In the Sky This Month – November 2009 November 7, 2009

Posted by Carl Hergenrother in Asteroids, Comets, Meteors, planets.
Tags: Asteroids, astronomy, comet christensen, comet howell, comet linear, comet siding spring, Comets, Juno, jupiter, leonids, mars, melpomene, Meteors, taurids, vesta
9 comments

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of November 2009. Jupiter continues its reign as not only king of the planets but king of the evening sky. November also brings the Leonids which may put on a good show for some observers this year.

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment and I’ll post them on the blog.

Planets

Jupiter - Jupiter continues to dominate the evening sky. At magnitude -2.4, Jupiter is ~10 times brighter than the brightest stars in the sky this month. Of all the planets, only Venus, and on very rare occasions Mars, are brighter.

Jupiter is located high in the southern sky by the end of dusk for easy observation. As has been the case all year, it is slowly moving through the southern constellation of Capricornus.

Nov 23 - Moon passes 3° from Jupiter

Neptune – For those with a telescope or binoculars and a dark sky, Neptune is located within 1/2 to 3/4 degrees of Jupiter. Jupiter will be a bright magnitude -2.4 while Neptune will be a faint +7.9. Even Jupiter’s 4 large Galilean moons are about a dozen times brighter than Neptune even though they are much smaller. The big reason for the faintness of Neptune is its distance from both the Earth and Sun. It is roughly 6 times further away from us and the Sun as Jupiter. The distance also explains its apparent small size of 2.3″. A good sized telescope will be required to see Neptune as anything other than a faint star.

Uranus – Uranus is located in western Pisces and is bright enough to be seen in small binoculars at magnitude +5.8 but will still require a telescope in order to see it as anything other than a star (it’s disk is only 3.5″ across).

Mars – Mars can be seen rising in the eastern sky late in the evening (~11 pm at the start of the month and ~9 pm at the end of the month). Mars is rapidly brightening and will reach magnitude 0.0 by the end of the month, matching that of many of the brightest stars visible in the morning sky. Mars will continue to brighten as it approaches its opposition on Jan 29 of next year. This month Mars marches through eastern half of the constellation of Cancer.

Nov 9 – Moon passes close (3°) to Mars

Venus - Venus rises an hour before dawn. When it is visible it is easily the brightest “star” in the sky. It was at its highest in the morning sky back in August and is continuing its slow crawl lower. It is located just above the horizon in the ESE sky right before the start of dawn. For binocular and telescope users, Venus will appear nearly full and is much smaller than it appeared this spring (now 11″ across versus 50″ last spring).

Nov 15 – Moon passes 6° from Venus

Mercury - Mercury starts the month behind the Sun with superior conjunction occurring on November 5. For the rest of the month, Mercury slowly pulls away from the Sun into the evening sky. Southern hemisphere observers will be able to catch a glimpse of Mercury low in the WSW sky during evening twilight. Northern observers will have to wait till December for their chance at seeing Mercury again.

Nov 5 – Mercury at superior conjunction

Saturn – Saturn is easy to observe during the last few hours of the night. Located in Virgo at magnitude +1.0, Virgo only rises right before the start of dawn. Telescope users should note that Saturn’s rings are still close to edge-on.

Nov 12 – Moon and Saturn within 7° of each other

Meteors

November hosts the sometimes great Leonids. In addition, the background rate of meteors is near an annual high. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During November, 12 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Leonids (LEO)

The Leonids have produced some of the most spectacular meteor displays in history. Rates as high as ~70,000 meteors per hour (that’s ~20 meteors per second) were seen in 1833 and 1966. Every ~33 years, the parent comet of the Leonids, Comet Tempel-Tuttle, returns to the vicinity of the Earth. For a few years after Tempel-Tuttle’s last perihelion in 1998, the Leonids produced enhanced rates of meteors as high as 100s to 1000s of meteors per hour.

What will 2009 bring? In a normal year, the Leonids produce maximum rates of ~10-15 meteors per hour. This year there are a number of predictions of enhanced activity.

J. Vaubaillon presents his predictions for this year’s Leonids at the website of the L’Institut de Mécanique céleste et de calcul des éphémérides (IMCCE). The Earth will encounter 4 dense dust trails produced by the Leonid parent comet. On November 17 at ~21:43 UT (or half an hour to an hour later), the Earth will encounter a trail produced in 1466 which may produce as many as ~115 meteors per hour from a dark site. At nearly the same time, November 17 at 21:50 UT, the 1533 trail may produce 80 meteors per hour. Combined the 2 trails may (may being the important word) produce ~200 meteors per hour. A display this strong would not be considered a “storm” but would be better than the Perseids or Geminids at their best by nearly a factor of 2. The predicted times favor observers in central Asia. Unfortunately for those of us in the US, we will miss out.

Two weaker and much more uncertain trails will be observable from the Western hemisphere. On November 17 at ~7:27 UT, the 1567 trail may produce 25 meteors per hour. Since this is in addition to the usual background rate of Leonids may result in total rates of 35-50 per hour which is comparable to last month’s Orionids. Also on November 18 at ~3:29 UT, the very old 1102 trail may enhance activity by 10-50 meteors per hour.

What does this mean? Most of us, especially in the United States, will only see the “normal” maximum on the morning of November 17 with hopefully an extra dozen or two meteors per hour from the 1567 trail. For those located in central Asia, a very good shower may be visible. The Leonids are best observed in the hours before sunrise. They will appear to radiate from the western part of the constellation of Leo.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Starting this month, info on most of the minor showers will be provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.

Northern and Southern Taurids (NTA/STA)

The Taurids never produce more than ~5 meteors per hour. They make up for their low rates by being active for over two months and by producing many bright fireballs. Their fireballs are more apparent to the average observer because, unlike most meteor showers, the Taurids are observable all night long rather than just in the morning. There is a chance that the Taurids will produce a higher number of fireballs this year than usual. There is a good chance that most fireballs being reported this month will be Taurids. They are active for the entire month of November with the northern branch (NTA) peaking around November 14. Though named after the constellation of Taurus, theTaurids radiate from a point between the constellations of Taurus and Aries this month.

The Taurids are produced by Comet 2P/Encke. Encke is an enigmatic object with the shortest period for any known comet at 3.3 years. First observed in 1786, it has been observed over ~60 orbits and has been seen every year since 1993.

Additional information on these showers and other minor showers not included here can be found at the following sites: Robert Lunsford’s Meteor Activity Outlook, Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2008 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

Comet 88P/Howell

P/Howell is an evening comet and currently the brightest in the sky. Howell is a short-period comet and takes only 5.49 years to orbit the Sun. Ellen Howell was a student at Caltech when she found the comet on photographic plates taken on 1981 August 29 with the 48″ Palomar schmidt.

In 1981 the comet was on an orbit that never brought it closer to the Sun than 1.62 AU (perihelion distance). As a result, it never got very bright. A relatively close approach to Jupiter in 1990 changed its perihelion distance to 1.40 AU. Further perturbations by Jupiter have decreased its perihelion distance to 1.36 AU. The closer perihelion distance allows the comet to get bright enough for small backyard telescopes. In addition, the comet seems to be running about ~2 magnitude brighter than usual. No obvious reason for the additional brightening has been observed yet.

This year perihelion occurred on Oct 12 so the comet is currently moving away from the Sun and should be fading. A day after perihelion I observed the comet from Tucson with a 12″ dobsonian. The comet was very difficult to observe from the city. At the time, I estimated its brightness at magnitude 8.5. The comet should be a little fainter (from 8.8 to 9.5) this month. The comet is located low in the southwest sky after dusk and will spend most of the month in Sagittarius. At mid-month P/Howell will be 1.41 AU from the Sun and 1.79 AU from Earth.

A finder chart for Comet Howell can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2006 W3 (Christensen)

This comet was discovered nearly 3 years ago on 2006 November 18 by Eric Christensen of the Catalina Sky Survey north of Tucson. At the time the comet was located 8.7 AU from the Sun which is nearly the distance of Saturn.

The comet reached perihelion at a rather distant 3.12 AU from the Sun on 2009 July 6. Because of its large perihelion distance, the comet will only slowly move away from the Sun and, though it will slowly fade, it should remain bright enough to be seen in modest sized backyard telescopes this month.

At mid-month, the comet is 3.37 AU from the Sun and 3.82 AU from Earth. Though observed as bright as magnitude ~8.2 it is now around magnitude 9.5 to 10.0. It is moving southeast while paralleling the summer Milky Way. This month the comet can be found in southern Aquila near the Sagittarius and is well placed for evening observing. This will probably be the last month that this comet will be observable in small scopes.

A finder chart for Comet Christensen can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet 217P/LINEAR

217P/LINEAR is also a short-period comet though it takes a little longer than Howell to circle the Sun, 7.83 years versus 5.49 years. P/LINEAR also comes closer to the Sun with perihelion at 1.22 AU from the Sun. The comet is already a month past perihelion which occurred on Sept 8.

P/LINEAR was first observed by the Lincoln Near Earth Asteroid Research (LINEAR) survey on 2001 June 21 though it wasn’t until 2001 July 11 that it was recognized as a comet. The 2009 apparition is the first return since the discovery apparition.

Though P/LINEAR and P/Howell have similar perihelion distances, LINEAR is a much fainter (or less active) comet. While Howell is ~9th magnitude at a rather distant 1.65 AU from Earth, P/LINEAR is a little fainter at magnitude ~10.0 though it is much closer (0.61 AU from Earth). This may be the last time to see P/LINEAR in small backyard telescopes until its 2048 return when it will pass within 0.40 AU of Earth. All the returns between 2009 and 2048 will be more distant.

I was able to observe 217P/LINEAR with 30×125 binoculars on the morning of Sept 25. In order to see the comet I had to drive out to a dark site. The comet was a rather nondescript smudge about 1.5′ across and with a brightness of magnitude 10.1. On Oct 16, I dragged my 12″ dob to a dark site. The comet was easy to observe with a nice short 0.08° long tail. At that time, the estimated brightness was magnitude 9.9.

This month the comet will be visible in the morning sky in the faint Milky Way constellation of Monoceros. It should remain at magnitude ~10 or a little fainter for the entire month. At mid-month the comet will be 1.49 AU from the Sun and 0.64 AU from Earth.

A finder chart for Comet LINEAR can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2007 Q3 (Siding Spring)

This long-period was first seen on 2007 August 25 by Donna Barton of the Siding Spring Survey in Australia. This past Oct. 7th the comet reached a rather distant perihelion at 2.25 AU from the Sun. Unfortunately, the comet and Earth are located on opposite sides of the Sun so the comet is rather far from Earth. Still the comet is observable before the start of dawn as a ~9.0 to 9.5 magnitude comet near the Leo/Virgo border. At mid-month the comet is 2.30 AU from the Sun and 2.71 AU from Earth.

A finder chart for Comet Siding Spring can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids (V < 9.0)

(3) Juno

Juno was the 3rd asteroid to be discovered after (1) Ceres and (2) Pallas. It was found by German astronomer Karl Harding on September 1, 1804. With dimensions of 320×267×200 km (192 x 160 x 120 miles) Juno ranks as the 10th largest asteroid in the Main Belt though it is the 2nd largest stony S-type asteroid.

This month it will be moving slowly southwestward in Aquarius. Peak brightness occurred at opposition on Sept. 22 when Juno was as bright as magnitude 7.6. In November it will fade from magnitude 8.4 to 8.9. Twenty degrees or so to the east of Juno is another bright asteroid, (18) Melpomene which is described in its own section.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Juno from Heavens Above.

(18) Melpomene

About 25 degrees to the east of (3) Juno lies another nice asteroid target for small telescopes. (18) Melpomene is located in the constellation of Cetus and is roughly the same brightness as Juno, in November it will fade from magnitude 8.3 to 9.0.

Melpomene is another stoney S-type asteroid and similar to Iris was also discovered by John Russel Hind. Found in 1852, it is his 5th of 10 asteroid discoveries.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Iris from Heavens Above.

(4) Vesta

Though not as large as Ceres, Vesta is more reflective making it the brightest asteroid in the Main Belt. Vesta is peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta is similar in size to Pallas with dimensions of 347×336x275 miles or 578×560×458 km. Vesta will also be visited by NASA’s Dawn spacecraft which will arrive in 2010.

Vesta is once again observable in the morning sky before the start of dawn. It is brightening from magnitude 8.1 to 7.7 as it travels eastward just north of Regulus in Leo.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Vesta from Heavens Above.

In The Sky This Month – September 2009 September 1, 2009

Posted by Carl Hergenrother in Asteroids, Comets, Meteors, planets.
Tags: Asteroids, astronomy, aurigids, comet christensen, comet kopff, Comets, juno. melpomene, jupiter, Meteors, september perseids, venus
55 comments

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of September 2009. Jupiter continues its reign as not only king of the planets but king of the evening sky.

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment and I’ll post them on the blog.

Planets

Jupiter -Jupiter continues to dominate the evening sky. Based on the comments left on this blog, many people have been noticing Jupiter in the southeast sky during the evening. At magnitude -2.8, Jupiter is ~13 times brighter than the brightest stars in the sky this month. Of all the planets, only Venus, and on very rare occasions Mars, are brighter.

Jupiter is already located high enough in the southest sky by the end of dusk for easy observation. Due to Jupiter’s location in the southern constellation of Capricornus , it never gets very high above the southern horizon this year.

Aug 2 – Nearly Full Moon passes within 3° of Jupiter and Neptune
Aug 29 – Moon within 3° of Jupiter

Chart of the sky during the middle of September showing the position of Jupiter. Chart created with Stellarium (www.stellarium.org).

Neptune – For those with a telescope or binoculars and a dark sky, Neptune is located within 1/2 to 3/4 degrees of Jupiter. Jupiter will be a bright magnitude -2.8 while Neptune will be a faint +7.8. That makes Jupiter over ~17,000 times brighter than Neptune. Even Jupiter’s 4 large Galilean moons are about a dozen times brighter than Neptune even though they are much smaller. The big reason for the faintness of Neptune is its distance from both the Earth and Sun. It is roughly 6 times further away from us and the Sun as Jupiter. The distance also explains its apparent small size of 2.3″. A good sized telescope will be required to see Neptune as anything other than a faint star.

Though Neptune wasn’t discovered until 1846, it was actually observed by Galileo on two occasions in 1612 and 1613. Similar to this month’s circumstances, Jupiter was passing very close to Neptune. Galileo observed and recorded Neptune as a star in the vicinity of Jupiter. There is also evidence that he noticed that Neptune had moved but didn’t follow up on it. So when you observe these 2 planets imagine what Galileo must have been thinking nearly 400 years ago.

Uranus – This month Uranus is at opposition which means it is at its closest to Earth and at its brightest. Uranus is located in western Pisces and is bright enough to be seen in small binoculars at magnitude +5.7 but will still require a telescope in order to see it as anything other than a star (it’s disk is only 3.5″ across).

Sept 17 - Uranus at opposition

Mars – Mars can be seen in the eastern sky during the 2nd half of the might. It rises around midnight though it won’t get high enough to clear most trees and building till about 1-2 am. At magnitude +0.9, its brightness matches those of many of the brightest stars visible in the morning sky. This month Mars marches through the constellation of Gemini. Mars will continue to brighten as it approaches its opposition on Jan 29 of next year.

Sept 13 – Moon within 1.1° of Mars

Chart of the sky on the morning of Sept 16. Chart created with Stellarium (www.stellarium.org).

Venus - Venus is the brightest “star” in the sky a hour or so before dawn. It was at its highest in the morning sky last month but now begins its slow crawl lower though it will remain an easy object for early risers over the next 2-3 months. For binocular and telescope users, Venus will appear nearly full and is much smaller than it appeared this spring (now 12″ across versus 50″ last spring).

Sept 16 – Moon passes 3° from Venus
Sept 20 – Venus within 0.5° of the 1st mag star Regulus

The Venus-Moon conjunction on the morning of Sept 16. Chart created with Stellarium (www.stellarium.org).

Mercury - For northern observers, Mercury is not visible until the last days of September when it can be seen as a 1st magnitude star rising in the east just before the Sun.

Sept 20 – Mercury at inferior conjunction (located between the Sun and Earth)

Saturn – Saturn is not visible this month as it is located on the opposite side of the Sun from Earth. As a result, it is located too close to the Sun in the sky to be easily observed. This is a shame because on September 4th, Saturn’s rings will be edge-on and would appear as a very thin line or even disappear in telescopes.

Sept 17 – Saturn at conjunction (located on the side of the Sun opposite Earth)

Meteors

September does not have many good showers though the background rate of meteors is near an annual high. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During September, 12 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

None this month.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

Aurigids (Max Date = Sept 1, Max ZHR = ~3 per hour)

The Aurigids are active from Aug 25 to Sept 8 with a peak on Sept 1. The shower is created by Comet Kiess, a comet only observed in 1911 though it should be back in ~70 years. The Aurigid shower is a minor one with a peak rate of 5 meteors per hour for observers under very dark skies.

This shower does have a history of producing short but spectacular outbursts. Reported outbursts in 1935, 1986 and 1994 allowed scientists to predict an outburst in 2007. The prediction was so good that the peak time was accurate to ~10 minutes. I was lucky enough to have observed this shower that only lasted for ~1 hour. At its maximum it produced a maximum ZHR of ~130 meteors per hour. Unfortunately no outbursts are predicted over the next 25 years, but you never know…

The shower appears to radiate from a position just to the east of the body of the constellation of Auriga. This shower is sometimes called the Alpha Aurigids.

September Perseids (Max Date = Sept 9, Max Rate = ~5 per hour)

The September Perseids are not related to the great Perseids of August. The showers were created by separate comets. This shower showed little sign of unusual activity until enhanced activity was observed on the night of Sept 9, 2008. That surprise display was also the topic of the very first Transient Sky post.

I have not seen any published research into last year’s high activity so its possible this years may see a repeat. Unfortunately, the moon will be bright and will drown out many fainter meteors.

Delta Aurigids (Max Date = Sept 28, Max Rate = ~3 per hour)

This weak shower appears the overlap the Sept Perseids and for some time they were considered part of the same shower. We now know that the showers come from different (though unknown) comets. The Delta Aurigids radiate from a point north of the body of Auriga and the bright star Capella.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

Comet C/2006 W3 (Christensen)

This comet was discovered over 2 years ago on 2006 November 18 by Eric Christensen of the Catalina Sky Survey north of Tucson. At the time the comet was located at 8.7 AU from the Sun which is nearly the distance of Saturn. The comet continues to move closer to the Sun and Earth and is currently 3.8 AU from the Sun and 3.4 AU from the Earth.

The comet is currently around magnitude 8.2 and should be at its brightest this month. It is moving southeast while paralleling the summer Milky Way. This month the comet will cross the constellation of Aquilia. The is well placed for evening observing.

The comet reached perihelion at a rather distant 3.12 AU from the Sun on 2009 July 6. Because of its large perihelion distance, the comet will only slowly move away from the Sun and though it will slowly fade from here on out it should remain bright enough to be seen in modest sized backyard telescopes for all of 2009.

A finder chart for Comet Christensen can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

22P/Kopff

All of the above comets are long-period comets which will not return to the inner Solar System for thousands to millions of years. Comet Kopff is a frequent visitor with an orbital period of 6.4 years. Discovered on 1906 August 20 by August Kopff of Germany, the comet has been observed during every subsequent return except one.

The comet reached perihelion at 1.58 AU from the Sun on May 25. Though now moving away from the Sun, the comet still moving closer to Earth and will be located 0.78 AU from us at the end of the month. Recent observations place the comet at magnitude 9.5 to 10.5. It is now slowly fading. The comet spends September in Aquarius.

A finder chart for Comet Kopff can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids (V < 9.5)

(3) Juno

This month it will be moving slowly eastward through Pisces. Peak brightness will come at opposition on Sept. 22 when Juno will be as bright as magnitude 7.6. A few degrees to the eats of Juno is another bright asteroid, (18) Melpomene which is described in its own section.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Juno from Heavens Above.

(18) Melpomene

Just a few degrees to the east of (3) Juno lies another nice asteroid target for small telescopes. (18) Melpomene is also located in the constellation of Pisces and is only a little bit fainter than Juno, brightening from magnitude 8.7 to 8.0 in September.

Melpomene is another stoney S-type asteroid and similar to Iris was also discovered by John Russel Hind. Found in 1852, it is his 5th of 10 asteroid discoveries.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Iris from Heavens Above.

In The Sky This Month – May 2009 May 1, 2009

Posted by Carl Hergenrother in Asteroids, Comets, Meteors, planets.
Tags: Asteroids, astronomy, comet cardinal, comet christensen, comet garradd, comet itagaki, comet stereo, comet yi-swan, Comets, eta aquarids, eta lyrids, Meteors, planets
3 comments

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of May 2009.

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment. I’ll post them here.

Planets

Mercury - Last month saw Mercury’s best evening apparition of 2009 (at least for Northern Hemisphere observers). Mercury is now descending back into the glow of the Sun. For the first week or so of the month it is still visible low in the west during evening twilight. Unlike last month, it is much fainter now (+0.9 magnitude on the 1st, +3.7 on the 11th).

Saturn – Saturn is the easiest planet to observe in May. By the end of twilight, Saturn is just south of zenith (straight up) under the eastern part of the constellation of Leo.

This year Saturn is dimmer than usual. At magnitude +0.8 to +0.9, there are at least a dozen stars that are brighter than it. The reason is the rings of Saturn contribute a lot to the brightness of Saturn. But this year, is a ring plane crossing year meaning that the rings are nearly edge-on. As a result, the rings are reflecting much less light in the Earth’s direction this year. Saturn’s appearance through a telescope will match the below image taken on April 23.

Image of Saturn by C. Hergenrother. April 23 w/ 12" with DMK41AF02 camera.

The Moon will pass a relatively distant 5.5 degrees to the south of Saturn on the evening of May 3.

Venus - Venus continues to slowly climb higher every night. It is currently a morning object and is best seen an hour before sunrise low in the eastern sky. For Southern Hemisphere observers, it will reach its highest point during the 2nd half of the month. For Northern observers, Venus will continue to climb higher until early August.

For binocular and telescope users, Venus will start the month as a large fat crescent, 39″ across and only 25% illuminated. By the end of the month, it will have shrunk to 25″ across but will also be nearly half illuminated at 46%.

Jupiter and Neptune - Jupiter rises a few hours before sunrise. By the end of the month, the king of the planets peaks above the horizon a little after midnight. Other than Venus, it is the brightest “star” in the morning sky at magnitude -2.2 to -2.4. Due to Jupiter’s location in the southern constellation of Capricornus , it never gets very high this year.

For those with a telescope or binoculars and a dark sky, Jupiter will pass close to the planet Neptune on the morning of May 27. At their closest, the 5th and 8th planet will only be 0.39 degrees apart. Jupiter will be a bright magnitude -2.4 while Neptune will be a faint +7.9. That makes Jupiter nearly ~12,000 times brighter than Neptune. Even Jupiter’s 4 large Galilean moons are about a dozen times brighter than Neptune even though they are much smaller. The big reason for the faintness of Neptune is its distance from both the Earth and Sun. It is roughly 6 times further away from us and the Sun as Jupiter. It’s distance also explains its apparent small size of 2.3″. A telescope will be required to see Neptune as anything other than a faint star.

Uranus – Uranus is located in western Pisces. It is bright enough to be seen in small binoculars at magnitude +5.9 but will still require a telescope in order to see it as anything other than a star (it’s disk is only 3.4″ across).

Both planets are early morning objects low in the southeastern sky.

Mars – Mars can be seen very low in the eastern sky all month long. At magnitude +1.2, it is only as bright as some of the brighter stars. Venus passed a distant 4 degrees to the north of Mars on April 24. Mars and Venus will continue to move apart until around mid-month when they will be 6.5 degrees apart. After that their distance from each other will shrink as they approach a 2 degree conjunction on June 21.

Meteors

The month of March experiences no major showers and only a few minor ones. It continues the annual lull in meteor activity from mid-January to mid-April.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During April, 8 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Eta Aquarids (ETA)

The Eta Aquarids are a major shower, especially for southern hemisphere observers, when they peak on May 5. For northern observers, the shower will only be observable for an hour or two before dawn. Since the radiant doesn’t get very high for NH observers, rates can be low. The radiant is located near the “jar” of Aquarius.

The ETA were produced by Comet Halley which also gives us the Orionids in October. Models suggest that the ETA were released by Comet Halley no later than 837 AD. The Orionids are easy to see because the particles are hitting the Earth from the anti-solar direction. This means the meteor shower can be seen in the middle of the night. The ETA are produced by meteoroids moving outbound from the Sun, as a result the radiant is located relatively close to the Sun. This means that the ETA radiant is only visible for an hour or so before twilight. By luck, the nearly Full Moon will have just set making the last hour of the night dark.

The shower spans from April 19 to May 28 with a peak around May 5 with a maximum ZHR of ~60.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

Eta Lyrids (ELY)

This shower is associated with Comet C/1983 H1 (IRAS-Araki-Alcock). The comet is a long-period comet which passed within 0.03 AU of the Earth on 1983 May 11. Discovered by astronomers using the Infrared Astronomical Satellite (IRAS) and two amateur astronomers, Genichi Araki (Yuzawa, Niigata, Japan) and George Alcock (Peterborough, England, UK), the comet brightened to 1st magnitude for a few days around closest approach.

Though the comet is now long gone and will not return for quite some time, particles released during past perihelia can be observed every year in early May. The Eta Lyrids are a minor shower that have never produce more than ~3 meteors per hour. Peak time in on May 8 though some meteors can be seen from May 3-12. Meteors will appear to radiate from a point in the middle of a triangle made up of the bright stars Vega and Deneb and the “head” of the constellation Draco. The Moon, Full on May 7, will spoil the Eta Lyrids for this year.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V < 8.0)

None

Small Telescope Comets (V < 10.0)

Comet C/2009 F6 (Yi-SWAN)

Comet C/2009 F6 (Yi-SWAN) is a long-period comet which will pass within 1.27 AU of the Sun on May 7. The comet is currently around magnitude 8.5 making it bright enough to be seen in small telescopes. Right now the nearly Full Moon will make observing the comet difficult but in a few days the Moon will not be a problem for evening observers. The comet is located northeast of the Sun. For southern hemisphere observers, you are out of luck. For northern observers, the comet can be observed in the evening sky.

The comet starts the month in Perseus. As it travels to the southeast, it will enter Auriga by the last week of the month. The comet will never get far from the horizon so a clear dark northwestern horizon is a must to see this comet. By mid-month the comet will be too close to the Sun for easy observation.

On the morning of April 21, I was able to observe Yi-SWAN with 30×125 binoculars. My observing location isn’t too dark with a limiting magnitude of ~+5.5. Even then, the summer Milky Way was faintly visible. The comet was barely visible as it was large and diffuse. Interestingly, the comet was not visible during multiple attempts to observe it during the evening hours. The darker morning sky most definitely helped. Unfortunately, in May the comet will not be visible in the morning.

The comet was found by Dae-am Yi of Yeongwol-kun, Gangwon-do, South Korea on March 26. He noticed the obvious blue-green glow of a comet on 2 images he took with a Canon 5D digital camera and a 90-mm f/2.8 lens. The other discoverer was Robert Matson of Irvine, CA. Mr. Matson found the comet on a series of images taken with the SWAN instrument on the SOHO (Solar Heliospheric Observatory) spacecraft starting on March 29.

A finder chart for Comet Yi-SWAN can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2008 Q3 (Garradd)

Sometimes comets surprise us. From time to time what appears to be a faint run-of-the-mill comet will undergo an outburst and brighten substantially. This is the case with Comet Garradd. Gordon Garradd of the Siding Spring Survey (Australia) used the 0.5-m Uppsala schmidt telescope to discover this comet back on 2008 August 27.

The comet was a faint 19th magnitude at discovery. With perihelion expected on 2009 June 23 at 1.80 AU from the Sun, it was expected to brighten but only to about 12th-14th magnitude. Two weeks ago the comet was sitting at 15th magnitude. Bright enough for CCD imaging but too faint for nearly all visual observers. On April 20th Micheal Jager imaged the comet and found it too be much brighter. Over the next few days, visual observers were able to confirm the outburst and estimated the comet to be as bright as magnitude 8.9.

Whether the comet will continue in its excited state and brighten further as it approaches perihelion is not known. It’s possible that the outburst will be short-lived and the comet may revert back to its original activity level.

Right now this comet is only observable from the Southern Hemisphere as it rockets through the constellations of Indus, Pavo, Apus, Triangulum Australe, and Circinus. For us up north, the comet will become visible in June as an evening object.

I hope to have a link to a finder chart for this comet up soon.

Comet C/2006 W3 (Christensen)

The comet is currently around magnitude 9.5 and will slowly brighten during the month. It is moving near the border of Lacerta and Pegasus. The comet is best seen in the early morning.

The comet will continue to brighten as it approaches perihelion at a still rather distant 3.12 AU from the Sun on 2009 July 6. At that time, the comet will be 8th magnitude and visible in many smaller backyard telescopes and even binoculars from dark sites. Christensen should remain bright enough to see in modest sized backyard telescopes for all of 2009.

On the morning of April 21, I was able to observe this comet with both 30×125 binoculars and a 12″ dobsonian. The comet was much easier to see in the 12″. Observation was made under a moderately light polluted sky with a limiting mag of ~+5.5.

A finder chart for Comet Christensen can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2009 G1 (STEREO)

Jiangao Ruan of China found this comet on images taken by the SECCHI HI-1B instrument onboard one of the STEREO spacecraft. The comet was first visible on images taken on April 3 UT. Similar to SOHO (a spacecraft that was used to co-discover Comet C/2009 F6 (Yi-Swan)), the two STEREO spacecraft study the Sun and its immediate environment.

With perihelion on April 16 at 1.13 AU from the Sun, the comet is now moving away from the Sun. Luckily it is still moving closer to the Earth, though it will get no closer than 1.06 AU from Earth. With a current estimated magnitude of ~9.0, the comet may brighten a bit as it gets closer.

The comet starts the month in southern Aquarius and will pass through Sculptor before finishing the month in the far southern constellation of Phoenix. It was never an easy object for northern observers and is now only observable from southern latitudes.

A finder chart for Comet STEREO can be found at Comet Chasing.

A nice collection of images can be found at Seiichi Yoshida’s Comet Homepage.

Comet C/2009 E1 (Itagaki)

This comet was found by amateur astronomer Koichi Itagaki of Yamagata, Japan on March 14. Comet C/2009 E1 (Itagaki) is a long-period comet which will come within 0.60 AU of the Sun at perihelion on April 7. It is also periodic in that it returns once every ~250 years according to the latest orbit.

This is the 1st comet to bear Koichi Itagaki’s name but it is not his 1st discovery. Back in 1968, he was a co-discoverer of Comet Tago-Honda-Yamamoto. Due to the rule that only the 1st 3 discoverers can have their name attached to a comet, his name was left off. Only a few months ago, he also re-discovered long-lost comet Giacobini.

The comet is located in the morning sky moving through Andromeda and to just north of the “square” of Pegasus. Due to its proximity to the Sun over the past few weeks, it hasn’t been observed since early April. At the time, it was magnitude 7.5-8.0. If it is still in the magnitude ~8.0 to 8.5 range then the comet will bright enough to be seen in a reasonably sized backyard telescope.

A finder chart for Comet Itagaki can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany).

Comet C/2008 T2 (Cardinal)

Rob Cardinal, an astronomer at the University of Calgary in Canada, discovered this comet last October. The comet was discovered as part of a survey at the Rothney Astrophysical Observatory for new Near-Earth asteroids at high declinations. In fact the comet was found within 10 degrees of the North celestial pole. At the time of discovery, the comet was ~14th magnitude.

At perihelion on June 13th of this year, the comet will pass within 1.20 AU of the Sun. The comet is currently ~9.0 to 9.5 magnitude as it moves south across Gemini into Canis Minor in the evening sky. The comet should continue to brighten by another magnitude this month. Similar to most comets, access to a clear western horizon is necessary to see it.

A finder chart for Comet Cardinal can be found at Comet Chasing and Aktuelle Kometen (in German).

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids (V < 10.0)

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below its surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres fades from from magnitude 8.0 to 8.4 as it ends is retrograde motion just north of Leo. If you are observing Saturn with a telescope or pair of binoculars, try your hand at finding Ceres with one of the finder charts linked below.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Ceres from Heavens Above.

(8) Flora and (14) Irene

Irene was discovered by John Russel Hind in 1851, being only the 14th asteroid known at the time (if you are wondering ~400,000 asteroids have been discovered to date, we’ve come a long way). It is an S-type asteroid with a stoney or silicate composition. Its takes 6.3 years to orbit the Sun. This month Irene will fade from magnitude 9.0 to 9.7 as it moves through central Virgo.

Though it is a bit fainter than the asteroids I usually present, those up for a challenge can spot the asteroid (8) Flora a few degrees away from Irene.

Flora is a large asteroid roughly 136×136x113 km in dimension. It is innermost large asteroid in the Main Belt. As a result, it can get bright enough for backyard observers with modest sized telescopes and binoculars. Flora is a stoney S-type asteroid and also the largest member of the Flora family. This family was created when a large impact occured on Flora. The other family members are pieces of Flora that were thrown off by the impact.

Flora starts the month at magnitude 9.9. By the end of the month, it has faded to 10.5. Flora and Irene provide us with a 2-for since both objects are located within 5 degrees of each other.

Since I have not been able to find a nice star chart showing the position of Irene and Flora, here is one I made with the C2A program. The bright star that Flora passes close to towards the end of the month (right side of the chart, white circle) is zeta Virginis.

flora_irene_may

In the Sky This Month – January 2009 January 1, 2009

Posted by Carl Hergenrother in Asteroids, Comets, Meteors, planets.
Tags: Asteroids, astronomy, broughton, ceres, christensen, Comets, euterpe, harmonia, kushida, lulin, Meteors, pallas, planets, quadrantids, vesta
87 comments

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of January 2009. The month starts off with Mercury and Jupiter close together in the evening sky. January also has one major meteor shower, the Quadrantids on Jan 3/4.

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment. I’ll post them here.

Planets

Venus rules the month of January. Located about 30-40 degrees above the southwest horizon, Venus is the brightest “star” in the sky for the first few hours of the night. Through a telescope, Venus appears like a brilliant half moon. The Moon will pass within 2.5 degrees of Venus on the night of the 30th.

Jupiter is located well below Venus in the west-southwest during the first week of January. After that Jupiter will be too close to the Sun to be seen.

Mercury is also visible a few degrees above Jupiter during the 1st week or so of January. It will be furthest from the Sun on the 4th and highest above the horizon on the 6th. By mid-month, Mercury will be too close to the Sun to be seen.

This month Saturn rises in the east around 11pm on the 1st and 9pm on the 31st. The best time to observe it, though, is when it is located directly overhead (5am on the 1st and 3am on the 31st). The Moon will pass close to Saturn on the night of the 15th.

Mars is still too close to the Sun to be seen.

Meteors

The month of January experiences 1 major shower, the Quadrantids, and only a few minor ones.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During November, six (6) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Quadrantids (QUA)

The Quadrantids are the best shower that you’ve probably never heard of. It’s bad enough that this shower peaks in the middle of winter in the northern hemisphere, but it is also named after a long defunct constellation. When first identified in the early 1800s, the meteors were observed to radiate from the small faint constellation of Quadrans Muralis (the Mural Quadrant). Unfortunately, the constellation didn’t make the cut when the official list of 80 constellations was set in 1930. Today, Quadrans Muralis and the radiant of the Quadrantids can be found north of the constellation of Bootes.

Another strike against observing the Quadrantids is their short duration. Showers, like the Perseids and Orionids, produce high rates of meteors for a few days near their maximum. The Quadrantids are only highly active for 12-24 hours. As a result, the shower can be missed if the peak does not coincide with your early morning observing.

This year there are 2 predictions for the peak. Based on past Quadrantid peaks, the International Meteor Organization predicts a peak on January 3 at 12h 50m UT. That’s 5:50 am MST or 4:50 am PST. If this prediction is correct, the Quadrantids will be best over western North America and probably pretty good for all of North America.

A second prediction is based on work by Jeremie Veubaillon and published in a chart in Peter Jenniskens’s book “Meteor Showers and Their Parent Comets”.It predicts an earlier peak on January 3 at ~1:00 UT. That’s in the early evening for North America at a time when the shower will not be easily visible. The Veubaillon prediction is based on all of the Quadrantids having been released during the break-up of a comet in 1490.

Last year rates reached as high as ~80 meteors per hour under a dark sky. Like most meteor showers, the Quadrantids are only observable early in the morning a few hours before dawn. The International Meteor Organization will post up-to-date observations of the activity level at their ZHR Live site.

Where do the Quadrantids come from? According to Peter Jenniskens, the Quadrantids are the result of an outburst of material or even the break-up of a comet in 1490. This comet was observed by Chinese, Korean and Japanese astronomers. In 2003, a new asteroid was discovered named 2003 EH1. It now appears that 2003 EH1 is either the same as the comet seen in 1490 or the largest surviving piece of that comet.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

Coma Berenicids (COM)

The Coma Berenicids are a minor shower with rates of ~5 meteors per hour at their peak. The shower is active from mid-December to late January as its radiant moves from southern Ursa Major through Coma Berenices and into Virgo. The shower may have been created by Comet C/1913 I (Lowe) a retrograde Halley-type comet. That is assuming Comet Lowe ever existed. There are some doubts that the comet was real since other observers were not able to observe the comet.

According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets” a number of meteor outbursts seen between the years of 609 AD and 764 AD may have caused by this shower.

Comets

Naked Eye Comets (V < 6.0)

There are no comets bright enough to be seen without binoculars or a telescope.

Binocular Comets (V < 8.0)

Comet C/2007 N3 (Lulin)

The brightest comet of the month can be seen low in the southeast right before dawn. Starting the month near the “head” of Scorpius, the comet will move into and cross the constellation of Libra during the month. Comet Lulin was discovered by the Lulin Sky Survey in Taiwan on 2007 July 11. At the time the comet was located beyond the orbit of Jupiter.

The comet will be closest to the Sun on 2009 January 10 at 1.21 AU from the Sun. It will be closest to Earth in late-February when it will be only 0.41 AU from us. At that time the comet may be as bright as 4th magnitude making it an easy object for binoculars and small telescopes. In fact, the comet will be visible to the naked eye as a small faint fuzzball from dark sites.

The comet is currently around magnitude 7.5 which makes it an easy object for binoculars and small telescopes from a dark sky. By the end of the month, it should be around magnitude 6 and perhaps visible to naked eye observers in very dark skies.

A finder chart for Comet Lulin can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Small Telescope Comets (V < 10.0)

Comet C/2006 W3 (Christensen)

The comet is currently around magnitude 10.2 and will slowly brighten during the month. It will be traveling south through the constellation of Lacerta and is nicely positioned for evening observing. I was able to observe the comet visually with my backyard 12″ reflecting telescope in November. Being small and condensed, the comet was fairly easy to see.

The comet will continue to brighten as it approaches perihelion at a still rather distant 3.12 AU from the Sun on 2009 July 6. At the time, the comet will be 8th magnitude and visible in many smaller backyard telescopes and even binoculars from dark sites. Christensen should remain bright enough to see in modest sized backyard telescopes for all of 2009.

A finder chart for Comet Christensen can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2006 OF2 (Broughton)

Similar to Comet C/2006 W3 (Christensen), C/2006 OF2 (Broughton) is another intrinsically bright comet with a large perihelion distance. It was the 2nd comet discovered by amateur astronomer John Broughton of Queensland, Australia. He first saw it on 2006 July 17 with a CCD-equipped 0.25-m telescope. At first, no cometary activity was detected and the object was classified as an asteroid. In late September of 2006, I was able to find evidence of cometary activity on images taken with the University of Arizona 1.54-m and the object was reclassified as a comet.

Comet Broughton passed perihelion on 2008 September 15 at a distance of 2.43 AU from the Sun. Based on its prior brightness behavior, it was not expected to be brighter than 10th magnitude. In the past few weeks, the comet has experienced a minor outburst in brightness. At its current magnitude of 9.8, the comet can be seen in large backyard telescopes. Moving south through the constellation of Auriga, the comet should fade as it moves away from both the Sun and Earth.

A finder chart for Comet Broughten can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet 144P/Kushida

Comet Kushida was discovered by Japanese amateur astronomer Yoshio Kushida back on 1994 January 8. With an orbital period of 7.6 years, this year marks its 3rd appearance since discovery.

The comet was not expected to get brighter than magnitude 10 or 11 but recently observers have estimated it is as bright as magnitude 8.8. With perihelion this January 26 at 1.44 AU from the Sun, the comet may brighten a little more over the next few weeks. It is currently retrograding through western Taurus.

A finder chart for Comet Kushida can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet 210P/Christensen

Yet another comet discovered by Eric Christensen may be visible in backyard scopes in January. This comet is a short-period comet with a period of 5.7 years. It is very faint except when close to the Sun. Perihelion occurred on December 19 at a distance of 0.53 AU from the Sun.

Alan Watson found Comet 210P/Christensen on images taken by the STEREO-B spacecraft on 2008 December 8 and 9. At the time, he thought the comet might be new until Maik Meyer suggested the STEREO comet was actually Comet 210P/Christensen. STEREO (which stands for Solar TErrestrial RElations Observatory) is a NASA mission to study the Sun and its immediate environment. Though not designed specifically to observe comets, its cameras have the ability to pick up bright comets close to the Sun. Quite often, these comets are too close to the Sun to be seen from Earth due to the scattering of sunlight by Earth’s atmosphere.

Though too close to the Sun to be seen from Earth, another spacecraft was able to see the comet as it sped past the Sun. Observations by the SOHO spacecraft estimated that the comet reached a brightness of 6th magnitude. The comet may still be bright enough for large backyard telescopes during the 1st half of January. The comet should be 9th-10th magnitude as it speeds through the constellation of Ophiuchus in the pre-dawn sky.

Asteroids

Binocular and Small Telescope Asteroids (V < 10.0)

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below the surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres is located in Leo brightening from magnitude 7.9to 7.2.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Ceres from Heavens Above.

(2) Pallas

Pallas is also a carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is large with dimensions of 350×334x301 miles or 582×556x501 km. This month it moves through the far southern constellations of Caelum and Eridanus. It fades from magnitude 8.0 to 8.2 over the course of the month.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Pallas from Heavens Above.

(4) Vesta

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Vesta from Heavens Above.

(27) Euterpe

Euterpe was the 27th asteroid discovered when it was first seen in 1853. It is an S-type asteroid with a stoney or silicate composition. With a diameter of 75 miles (125 km) it much smaller than Ceres, Pallas or Vesta. The reason it can get as bright as them is due to its orbit which brings it closer to the Sun and Earth. This month Euterpe will be roughly 1 AU from Earth and 2 AU from the Sun.

This month Euterpe will brighten from magnitude 9.7 to 8.9 as it moves from Leo into Cancer. The asteroid will be at its brightest in early February at magnitude 8.8.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Euterpe from Heavens Above.

(40) Harmonia

[Thanks to Sam Millar for calling attention to this asteroid.]

Harmonia just barely makes the cut this month. Starting the month at magnitude 9.9, it peaks in brightness on January 12 at 9.5. By the end of the month, Harmonia is back below 10th magnitude.

Similar to Euterpe, Harmonia is a stoney silicate-rich S-type in the inner Main Belt. At opposition on the 12th, it will be 2.30 AU from the Sun and 1.31 AU from Earth.

Finder chart for Harmonia from Heavens Above.

In The Sky This Month – December 2008 December 1, 2008

Posted by Carl Hergenrother in Asteroids, Comets, Meteors, planets.
Tags: Asteroids, astronomy, ceres, christensen, Comets, geminids, jupiter, lulin, mcnaught, mercury, Meteors, metis, planets, saturn, ursids, venus, vesta
3 comments

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of December 2008. The biggest event of the month will be the Venus-Jupiter-Moon conjunction on the 1st. On the 13th, the Geminid meteor shower will peak. Though usually one of the best showers of the year, the Full Moon will ruin the show.

Planets

Venus and Jupiter start off the month in grand fashion. On the 1st, the two are located in the south-southwest just after sunset within 2 degrees of each other. Venus is by far the brighter of the pair. Not that Jupiter is a slouch only being the brightest “star” in the sky after Venus. To add to the sight, a thin crescent Moon will be located just to the upper left of the pair.

As the month progresses, Venus will rapidly move away from Jupiter. Venus will appear to start each evening higher and higher in the sky. Jupiter, on the other hand, will quickly drop towards the horizon and by the end of the month, will be located close to the southwest horizon. But Jupiter will not be alone and ends the month within 1.3 degrees of the innermost planet Mercury. The Moon can also be used at the end of the month to find the evening planets as it passes close to Jupiter and Mercury on the 29th and Venus on the 31st.

This month, Saturn starts to rise before midnight. The best time to observe it, though, is just before the start of dawn when it will be located high in the sky in the constellation of Leo. The Moon will pass close to Saturn on the nights of the 18th and 19th.

Mars is too close to the Sun to be seen.

Meteors

The month of December experiences 2 major showers, the Geminids and the Ursids, and a slew of minor ones.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During November, twelve (12) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Geminids (GEM)

Along with the Perseids of August, the Geminids are one of the best meteor showers delivering great displays year after year. Unfortunately, this year sees the worst circumstances possible for Geminid watching as the nearly Full Moon is located right next to the radiant. Similar circumstances occurred in October for the Orionids but observers were still able to see quite a few meteors.

According to Sirko Molau’s analysis of video data, the Geminids are already observable at the beginning of the month though their rates are very low. The peak is predicted for the nights of December 13-16. With a radiant near the star Castor in the constellation of Gemini, the Geminids are one of the rare major showers that are observable before midnight and can be observed as early as 8:00 pm though rates are usually best after 10:00 pm. Under a dark rural moon-less sky, the Geminids can produce as many as 100+ meteors per hour. With the bright Moon, rates of a few tens of meteors per hour may still be observed.

The Geminids are the result of the break-up and subsequent activity of the “asteroid” Phaethon. Why asteroid in quotes? Most meteor showers come from comets yet Phaethon is on a very non-cometary orbit and has never shown any cometary activity. There is still much scientific discussion about what exactly Phaethon is.

More details on the Geminids and their parent “asteroid” Phaethon will be posted as we get closer to its peak.

Ursids (URS)

The Ursids will produce up to 10 meteors per hour at their peak on December 22-23. That rate makes it a borderline major/minor shower though the Ursids have experienced a number of outbursts in the past. With a radiant near the “bowl” of Ursa Minor (the “Little Dipper”), this shower is also observable all night long though the best time to observe it is during the last hours of the night. More details on the Ursids and their parent comet, Comet Tuttle, will be posted later.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

December Phoenicids (PHO)

The December Phoenicids (also just called the Phoenicids) radiate from the far southern constellation of Phoenix. Due to its southern radiant, this shower is very difficult to observe from the Northern Hemisphere. The shower results from the break-up or splitting of Comet P/1819 W1 (Blanpain) in 1819. Most years the shower only produces a few meteors per hour but on occasion up to 100 meteors per hour have been seen (1887, 1938 and 1956). No further outbursts are predicted until 2050 though that doesn’t mean we can’t be surprised. The shower is predicted to peak on December 6. In 2003, the barely active nucleus of Comet Blanpain was re-discovered by the Catalina Sky Survey.

Puppid/Velids (PUP)

These showers are another two for the southern hemisphere. There is evidence that the Puppids and the Velids are part of a much larger complex of showers that span from November through February. Their orbits suggest they are the result of the break-up of a yet-to-be-discovered comet or asteroid on a high inclination orbit (50-70 degrees). At their best, Puppid/Velids produce 5-10 meteors per hour for those south of the equator. Not too many are visible for northern hemisphere observers.

Monocerotids (MON)

The December Monocerotids (sometimes just called the Monocerotids) are produced by Comet C/1917 F1 (Mellish). Discovered in 1917 this bright comet is on a ~145 year orbit and isn’t due back till around 2062. There is evidence that this shower may have produced a number of bright fireballs during the 11th through 16th century. The shower is predicted to peak on December 7th-9th with a paltry 2 meteors per hour radiating from the faint constellation of Monoceros (located just east of Orion).

σ-Hydrids (HYD)

With a peak on December 9th of only 3 meteors per hour, these meteor from the “head” of the constellation of Hydra will be difficult to observe by all but the most advanced observers. Not much is known about this shower other than it was created by an unknown long-period or Halley-type comet with a perihelion of ~0.25 AU and an inclination of ~125 to 130 degrees.

Coma Berenicids (COM)

The Coma Berenicids are another minor shower with rates of ~5 meteors per hour at their peak. The shower is active from mid-December to late January as its radiant moves from southern Ursa Major through Coma Berenices and into Virgo. The shower may have been created by Comet C/1913 I (Lowe) a retrograde Halley-type comet. That is assuming Comet Lowe ever existed. There are some doubts that the comet was real since other observers were not able to observe the comet.

According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets” a number of meteor outbursts seen between the years of 609 AD and 764 AD may have caused by this shower.

Comets

Naked Eye Comets

There are no comets bright enough to be seen without binoculars or a telescope.

Binocular Comets

Comet C/2007 N3 (Lulin)

The brightest comet of the month is not visible for the 1st half of the month. Comet Lulin will be too close to the Sun until after mid-month when it will be visible low in the southeast (near the “head” of Scorpius) at the start of dawn. Comet Lulin was discovered by the Lulin Sky Survey in Taiwan on 2007 July 11. At the time the comet was located beyond the orbit of Jupiter.

In December the comet should brighten from 7th magnitude to 6th. I say “should” because the comet has not been seen since late October because it has been too close to the Sun. As a result, we don’t know how bright Lulin is right now. Baring a new discovery or unforeseen outburst, Comet Lulin may be the best comet of 2009.

A finder chart for Comet Lulin can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Small Telescope Comets

Comet C/2008 A1 (McNaught)

Comet McNaught is a long-period comet that passed closest to the Sun on Sept 29 at a distance of 1.07 AU (100 million miles or 160 million km). It was the first comet discovered in 2008 having been found by Robert McNaught of the Siding Spring Survey back on January 10. It was McNaught’s 43rd comet discovery.

The comet is only visible from the Northern Hemisphere and during December it travels through northern Ophiuchus into southern Hercules. After getting as bright as 6th magnitude at perihelion, the comet will slowly fade from magnitude 8.8 to 10.0 during the month. This will probably be the last month to see this comet in regular sized backyard telescopes.

A finder chart for Comet McNaught can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet C/2006 W3 (Christensen)

The comet is currently around magnitude 10.2 and will slowly brighten during the month. It will be traveling south through the constellations of Cepheus and Lacerta and is nicely positioned for evening observing. I was able to observe the comet visually with my backyard 12″ reflecting telescope a few weeks ago. Being small and condensed, the comet was fairly easy to see.

A finder chart for Comet Christensen can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Comet P/2003 K2 (Christensen)

Yet another comet discovered by Eric Christensen may be visible in backyard scopes in December. This comet is a short-period comet with a period of 5.7 years. It is very faint except when close to the Sun. With perihelion predicted for 2009 January 8 at a distance of 0.53 AU from the Sun, the comet may be bright enough for backyard observers by the end of the month.

There are a lot of question marks about this comet. It was only observed for 1 month in 2003 and those observations were made after perihelion. The comet has yet to be observed during this return and its exact location is unknown. Plus since the comet has never been observed before perihelion we don’t know how bright it should be. Hopefully the comet will be picked up in the next few weeks. When/if that happens, we’ll have a better idea of how observable it will be.

Asteroids

Binocular and Small Telescope Asteroids

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below the surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres is located high in the sky right before sunrise in Leo brightening from magnitude 8.3 to 7.9.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(2) Pallas

Pallas is also a carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is large with dimensions of 350×334x301 miles or 582×556x501 km. This month it moves through the far southern constellations of Columba and Caelum. It peaks at magnitude 8.0 over the course of the month.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(4) Vesta

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(9) Metis

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

Report on the Impact of 2008 TC3 November 5, 2008

Posted by Carl Hergenrother in Asteroids, Fireballs.
Tags: 2008 TC3, Asteroids, astronomy, Fireballs
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The Near-Earth Object Program office at NASA-JPL has just released a report about the impact of 2008 TC3. TC3 was the small asteroid discovered less than a day before entering the Earth’s atmosphere over northern Sudan. The text of the report can be found at:

http://neo.jpl.nasa.gov/news/2008tc3.html

Some highlights from the report include …

Discovered on 2008 Oct 6 at 6:39 UT by Richard Kowalski at the Catalina Sky Survey using the Mount Lemmon 1.5-m telescope, north of Tucson, Arizona
26 observatories reported 570 astrometric (positional) observations
2008 TC3 entered the atmosphere on 2008 Oct 7 at 2:45:40 UT
It detonated (exploded) 5 seconds later due to the high pressure of rapidly moving through the Earth’s dense atmosphere
TC3 was moving at 12.4 km/s when it hit the atmosphere. That’s 7.4 miles/s or 26,640 miles per hour!
It was tumbling as it moved through space and rotated about two axes with periods of only 97 and 49 seconds. Those periods are how long a “day” (sunrise to sunrise) would have lasted on TC3. This is not uncommon for small asteroids.
It was the first natural body other than the Moon to be eclipsed by the Earth. It entered Earth’s shadow an hour before it hit the atmosphere.
TC3 detonated at a rather high altitude for a large fireball (37 km or 22 miles or 117,000 feet). This suggests that TC3 was rather weak when compared to most asteroids/meteorites.
The fireball and/or flash was observed by a European weather satellite, US Defense satellites, a KLM flight crew and a video security camera in southern Egypt.

In The Sky This Month – November 2008 November 1, 2008

Posted by Carl Hergenrother in Asteroids, Comets, Meteors.
Tags: Asteroids, astronomy, ceres, Comets, d'arrest, leonids, mcnaught, Meteors, metis, pallas, sporadics, taurids, vesta
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This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of November 2008.

Planets

Venus is the very bright “star” close to the southwestern horizon for an hour or so after sunset. When it is above the horizon, it is the brightest “star” in the sky. Every night Venus will appear to be a little bit higher in the sky. As the month progresses Venus will also appear a little further to the south. Venus starts the month in the constellation of Ophiuchus. It crosses into Sagittarius by the 2nd week of the month. By the end of the month, Venus will be located very close to Jupiter (within 2 degrees).

Jupiter is located in the constellation of Sagittarius. At the beginning of the month, Jupiter starts the night low in the southwestern sky and sets around 9 pm. As the month progresses, it will appear lower in the sky and further to the west. Jupiter is fainter than Venus but brighter than any star. As mentioned in the Venus section above, Jupiter will close in on Venus all month. By the end of the month, Jupiter and Venus will be located within 2 degrees of each other.

Saturn is located high in the east just before sunrise in the constellation Leo. It is as bright as many of the brightest stars.

Mercury is located low in the east-south-east right before sunrise. By the 2nd week of the month it is too close to the Sun to be seen. Mercury won’t be observable again until mid-December.

Mars is too close to the Sun to be seen.

Meteors

November sees a number of meteor showers including the Leonids which have produced spectacular storms in the past.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During November, sixteen (16) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Leonids (LEO)

What will 2008 bring? Well first off, this is a bad year with regards to the Moon. Similar to October’s Orionids, the Moon will be bright and close to the Leonid radiant during their peak limiting the number of fainter meteors that can be seen. In a normal year, the Leonids produce maximum rates of ~10-15 meteors per hour. The Moon will cut those rates in half or more.

There are 2 predictions for enhanced activity this year. The International Meteor Organization summarizes this year’s prediction with the following taken from their 2008 Meteor Calendar:

The Leonids may produce just a normal maximum close to their ‘traditional’ nodal time in 2008, on November 17, around 09h UT, though the bright waning Moon will be a severe problem if so. However, Mikhail Maslov proposed that the shower may show a peak with ZHRs ~ 130 at 00h22m UT on November 17 in WGN 35:1 (2006, p. 7), with meteors brighter than average. Many of his other model calculations for the Leonids in the period 2001 — 2006 showed some differences to what was actually observed, so while this this is an interesting possibility for 2008, its accuracy is unknown and unproven. Jérémie Vaubaillon finds instead two potential stream encounters, centred on November 17 at 01h32m UT (1466 trail; ZHR most uncertain — perhaps ~ 50, but maybe ~ 25 — 100) and November 18 at 21h38m UT (1932 trail; ZHR possibly ~ 20 at best?). Checking on all these times (or any others that may be suggested subsequently) will be difficult due to the Moon, but valuable.

What does this mean? Most of us, especially in the United States, will only see the “normal” maximum on the morning of November 17 with low rates due to the bright Moon. For those located throughout Eurasia, one, two or three of the possible outbursts may be observable. The Leonids are best observed in the hours before sunrise. They will appear to radiate from the western part of the constellation of Leo.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

Orionids (ORI)

When you see an Orionid meteor, you are seeing small pieces of Halley’s Comet which were released thousands of years ago. The Orionids were the best shower during the month of October. At their peak, Orionids appear to radiate from a point in the constellation of Orion, hence the name Orionids. Meteor shower radiants are not stationary and on average move about a degree per day towards the east. As a result, in November the Orionids actually appear to radiate from the southwestern Gemini. Though they peaked around Oct 21, a few Orionids will be observable after midnight till the middle of November.

Northern and Southern Taurids (NTA/STA)

Comets

Naked Eye Comets

There are no comets bright enough to be seen without binoculars or a telescope.

Binocular Comets

Comet C/2008 A1 (McNaught)

Comet McNaught is a long-period comet that will passed closest to the Sun on Sept 29 at a distance of 1.07 AU (100 million miles or 160 million km). It was the first comet discovered in 2008 having been found by Robert McNaught of the Siding Spring Survey back on Jan 10. It was McNaught’s 43rd comet discovery.

The comet is only visible from the Northern Hmisphere and during November it crosses the constellation of Ophiuchus. The comet will slowly fade from magnitude 7.5 to 8.5 during the month. I was able to observe this comet with my 12″ Dobsonian from my backyard in Tucson. The comet was not an easy object to see even in a large telescope from a site with moderate light pollution. Dark skies will definitely help with this one. From dark skies, it can be seen in binoculars or a small telescope. From brighter skies, a telescope is required.

A finder chart for Comet McNaught can be found at Comet Chasing.

Small Telescope Comets

Comet 6P/d’Arrest

Comet 6P/d’Arrest was one of the first short-period comets to be observed. First seen by the Frenchman Philippe de la Hire in 1678, the comet was definitively discovered by Heinrich Louis d’Arrest of Germany on 1851 June 28.

Comet d’Arrest is in a short-period orbit with a period of 6.5 years. It passed closest to the Sun back on Aug 14 at a distance of 1.35 AU (125 million miles or 200 million km). The comet is a very difficult object for observers in the Northern Hemisphere because it is located in the southern constellation of Sculptor. Even though it will slowly move north this month, observing conditions will not improve because the comet will also fade from magnitude ~9.5 to ~11.0 by month’s end. This comet will definitely require a telescope and dark skies to be seen.

A finder chart for Comet d’Arrest can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below the surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres is located low in the eastern sky right before sunrise in Leo brightening from magnitude 8.6 to 8.4.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(2) Pallas

Pallas is also a carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is large with dimensions of 350×334x301 miles or 582×556x501 km. This month it moves from the southern constellation of Lepus into the even further southern constellation of Columba. It brightens from magnitude 8.2 to 8.0 over the course of the month.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(4) Vesta

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(9) Metis

Metis was discovered in 1848 by Andrew Graham of Ireland. It is a S-type asteroid with a composition similar to stony meteorites (ordinary chondrites). With a diameter of 140×120x85 miles or 235×195×140 km, it is much smaller than Ceres, Pallas or Vesta. Metis will be at opposition and also at its brightest (magnitude 8.5) on November 4. Opposition is also the moment when Metis will be closest to Earth this year at a distance of 1.14 AU. During the rest of the month, it will slowly fade to magnitude 9.1 as it travels through Aries just a few degrees south of Vesta.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

The Orionid Meteor Shower October 18, 2008

Posted by Carl Hergenrother in Meteors.
Tags: Asteroids, meteor shower, Meteors, orionids
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Back in 1986, Halley’s Comet returned after a 76 year journey through the outer solar system. Not predicted to return again until 2061, you might think you missed your chance to see Halley. Well, yes and no. It will be a long time before anyone sees the comet again, but twice a year small pieces of Halley are visible as they burn up in the Earth’s atmosphere. Both the Eta Aquarid meteor shower in early May and the Orionids of mid-October were created by small dust particles released over thousands of years by Comet Halley.

Comet Halley is one of the most active and brightest known comets. Though there are brighter comets than Halley, it is the brightest comet which returns after a reasonable length of time (~76 years). As a result, it has been observed at 30 returns dating back to 239 BC. It was likely observed even earlier but those records have not survived. Halley travels in an orbit that takes it from as far as 35 AU (just beyond the orbit of Neptune) from the Sun to as close as 0.59 AU (just inside the orbit of Venus) from the Sun. It’s orbit is inclined 162 degrees from the Earth’s orbit. This means the comet orbits the Sun in almost the exact opposite direction than the Earth and the other planets which is common for comets with orbital periods greater than ~30 years. Two plots of Halley’s orbit are posted below.

Outer Solar System view of the orbit of Comet Halley. Image created at http://neo.jpl.nasa.gov/orbits/

Inner Solar System view of the orbit of Comet Halley. Image created at http://neo.jpl.nasa.gov/orbits/

What exactly are the Orionids?

Comets are mountain sized rocks which contain a large amount of ices (water, carbon monoxide, methane, and many others). Every time a comet passes close to the Sun, these ices sublimate (go directly from a solid to a gas). As the gases build up inside the comet, they eventually erupt into space much like geysers on Earth. These geysers of gas (on comets they are called “jets”) carry lots of dust with them. It is all of this escaping gas and dust that gives comets their “fuzzy” appearance. Over time the dust particles spread out and line the entire orbit of the comet. As a result, even though the comet may be far away (right now Halley is beyond the orbit of Neptune) dust can be found at any point in Halley’s orbit. When the Earth passes close to the orbit of Halley we can see some of this dust as it burns up in the atmosphere as meteors.

Over time the orbit of Halley changes. Computer simulations of the past movements of Halley and its dust suggest that many of this year’s Orionid meteors were released by Halley between 1265 BC and 910 BC (for some points of reference, the Trojan War took place around 1200 BC and King David ruled around 1000 BC).

So what can we expect this year and when should you look?

This Orionid meteor shower is usually active from Oct 3 to Nov 11 with a broad peak between Oct 18 and 24. During their peak, rates can be as high as 20-70 meteors per hour. Last year rates reached 70 meteors per hour and similar circumstances are predicted for this year with the best time being the morning of Oct 19 (for the US). However, a bright quarter Moon will wash out many of the fainter meteors resulting in smaller rates. Due to the bright Moon, rates may only be 1/3 as high as last year.

The Orionids appear to come from an area in northern Orion (marked by a yellow X in an O on the sky chart below). This area, called the radiant, rises around 10pm local time. It is best to wait till the radiant is high in the sky before looking for meteors (say 1am). The radiant is highest around 3:30am which is the best time to look. As you can see on the sky chart, the Moon is almost on top of the radiant. Meteors can appear anywhere in the sky so you don’t have to look at the radiant. In fact, with the Moon nearby, it is best to look without having the Moon in your line of sight.

If you live in a major city with only a few bright stars visible, you will not see too many, if any, meteors. It is always best to observe from a dark site. But due to the Moon, even dark sites may only see 10-20 meteors per hour. The International Meteor Organization has a near real-time graph of the activity level of the Orionids at this page. Note that the rates shown have been compensated for bright skies and moonlight (meaning this is the rate you would have seem if there was no Moon and you were observing from a dark rural location). The actual rate of meteors will be lower (perhaps much lower) due to the Moon and if you are at a site with bright skies.

Additional information on the Orionids can be found at the American Meteor Society.

Chart of the sky for 3:30 AM from the Northern mid-latitudes for mid-October. The Moon

More on the Sudanese fireball – 2008 TC3 October 8, 2008

Posted by Carl Hergenrother in Asteroids, Fireballs.
Tags: 2008 TC3, Asteroids, astronomy, fireball
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The fireball caused by the impact of 2008 TC3 has been confirmed. The NASA’s Near-Earth Object Project Office reports that the fireball was observed on October 7 at 02:45:45 UT. The energy released was estimated at 0.9 to 1.0 kilotons of TNT. They do not give the source of this information though they state that more information is forthcoming. My guess, is this sighting is from the US Department of Defense’s Defense Satellite Program (DSP) satellites. The DSP program consists of a constellation of missile early warning satellites which monitor most of the world for missile launches. These satellites are also very good at detecting bright fireballs. Hopefully more details will become available.

The NEO Project Office also reports that an infrasound station in the African nation of Kenya made a detection. Dr. Peter Brown of University of Western Ontario in Canada estimates the energy released at 1.1 to 2.1 kilotons of TNT. A third report comes from a pilot on a KLM flight over the nation of Chad who saw a flash at the time of the fireball. More info on this last two reports can be found at Spaceweather.com.

The fact that there are no videos of this fireball are disappointing but not surprising. The fireball occurred over northern Sudan which is sparsely populated and rather poor. Sudan is also not a country that you can just show up and drive around in. It would have been difficult to have traveled to the fireball site. It will be interesting to see if any meteorites are found on the ground from this fireball. Even with all of the difficulties of travel in Sudan, I’d be surprised if a few meteorite hunters don’t find their way to the predicted impact site.

[Exciting new news]

An image of the fireball taken from a European weather satellite has been posted by Jiri Borovicka of the Czech Academy of Sciences. The image can be found on the frontpage of Spaceweather.com. More info on the this sighting can be found at the webiste of the EUMETSAT.

Incoming Fireball Over Sudan!!! – 2008 TC3 October 7, 2008

Posted by Carl Hergenrother in Asteroids, Fireballs.
Tags: 2008 TC3, Asteroids, astronomy, Fireballs
12 comments

For the first time in recorded history a very small asteroid has been discovered before burning up in Earth’s atmosphere as a brilliant fireball. During the night of Oct 5/6, Rich Kowalski of the Mount Lemmon Survey discovered a new Near-Earth asteroid named 2008 TC3. It now appears that this object will hit the atmosphere of the Earth tonight (Oct 7 UT) at 2:46 UT (10:46 EDT) over northern Sudan in northeast Africa.

Based on the brightness of this asteroid, it is very small and probably on the order of 2-meters or 7-feet in diameter. As big as this may seem, objects this small usually break up into much smaller pieces with little remaining to hit the ground. If pieces do survive to hit the ground they will probably be small, no bigger than a grapefruit. What this object will do is produce a spectacular fireball for a few tens of seconds over the Sudan. The Near-Earth Object Project Office at NASA-JPL estimates that an event of this size occurs once every few months somewhere in the world. The fireball will probably be more spectacular than the Sept 19 fireball observed over southern California but will only be visible within a few hundred miles of northern Sudan. It will not be visible from the rest of the world.

This is the first time a small fireball producing asteroid has been observed before entering the Earth’s asteroid. Why hasn’t this happened before? Object of this size are very faint. In fact, of the 360000+ known asteroids, we have only found 2 other asteroids that are this small. Also asteroids very close to Earth move very fast. Now moving fast isn’t the problem, the problem is that there is so much junk in orbit around the Earth from decades of satellite launches, that it is very hard to tell the difference between a small close asteroid and an old satellite. So the current asteroid hunting telescopes have to be lucky to pick one of these objects up. In the future, the next generation of asteroid survey telescopes will be able to discover these objects further out. There may come a time in the not too distant future, when a spectacular fireball will be predicted to occur over a major population center days in advance. When that day happens, you won’t have to be lucky to see a fireball, you can just go outside at the predicted time and enjoy the show.

Before it hit the Earth’s atmosphere, 2008 TC3 was on an orbit that took it as close to the Sun as 0.91 AU and as far from the Sun as 1.63 AU. It took 1.43 years to orbit the Sun.

If any photos of the fireball become available I will post link to them.

Links to a few publications about 2008 TC3…

The discovery announcement from the Minor Planet Center

Press release from the University of Arizona

Press release from the Near-Earth Object Project Office at NASA JPL

older posts »

The Transient Sky – Comets, Asteroids, Meteors

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In The Sky This Month – May 2009 May 1, 2009

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In the Sky This Month – January 2009 January 1, 2009

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In The Sky This Month – December 2008 December 1, 2008

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Report on the Impact of 2008 TC3 November 5, 2008

In The Sky This Month – November 2008 November 1, 2008

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Meteors

Comets

Asteroids

The Orionid Meteor Shower October 18, 2008

More on the Sudanese fireball – 2008 TC3 October 8, 2008

Incoming Fireball Over Sudan!!! – 2008 TC3 October 7, 2008

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