In The Sky This Month – December 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of December 2010.

December 2010 Highlights
* Great Total Lunar Eclipse for the Americas and Eastern Asia on Dec 21
* Geminid Meteor Shower peaks on Dec 14
* Jupiter dominates the evening sky, while…
* Venus dominates the morning sky
* Comet 103P/Hartley 2 slowly fades as it moves away from the Earth and Sun

Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Moon - The big event this month is a Total Lunar Eclipse on the night of Dec 20/21. The Moon will be located nearly overhead during the peak of the eclipse for North American observers.

The start of the umbral eclipse (when the darkest part of Earth’s shadow covers the Moon) will occur at 6:32 UT (1:32 EST / 12:32 CST / 11:32 MST / 10:32 PST) with mid-eclipse at 8:16 UT (3:16 EST / 2:16 CST / 1:16 MST / 12:16 PST)

The table below lists important lunar dates for the month, including the phases of the Moon and nights of lunar-planetary and lunar-stellar conjunctions.

Dec 1 - Moon 7° from Saturn
Dec 2 - Moon 6° from Venus and 3° from Spica
Dec 5 - New Moon
Dec 6 - Moon 0.8° from Mars
Dec 7 - Moon 2° from Mercury
Dec 11 - Moon 5° from Neptune
Dec 13 - First Quarter Moon 7° from Jupiter
Dec 14 - Moon 6° from Uranus
Dec 19 - Moon 1.5° from Pleiades and 8° from Aldebaran
Dec 21 - Full Moon and Total Lunar Eclipse
Dec 23 - Moon 8° from Pollux
Dec 24 - Moon 4° from Beehive Cluster
Dec 25 - Moon 5° from Regulus
Dec 28 - Third Quarter Moon 7° from Saturn
Dec 29 - Moon 3° from Spica
Dec 31 - Moon 7° from Venus

Mercury – Mercury is in the middle of a evening apparition at the start of the month. It’s all downhill (literally) after that as the innermost planet creeps back into the bright twilight and out of view by mid-month. At the end of the month Mercury is back as it peeks above the SE horizon right before dawn.

Dec 1 - Greatest Elongation East
Dec 7 - Moon 2° from Mercury 

Mars - Mars is practically out of view this month for most of us. Those with exceptionally clear skies and unobstructed view of the SW sky in the evening might still catch a glimpse of this +1.3 magnitude planet.

Dec 6 - Moon 0.8° from Mars

Jupiter (and Uranus, too...) - The 'King of the Planets' continues his reign as the uncontested 'King of the Evening Sky'. though fading from magnitude -2.5 to -2.3, nothing but the Moon rivals it in brightness. Located on the Pisces/Aquarius border, Jupiter is easy to find in the south-south-east as it gets dark.

If you have a pair of binoculars or small telescope take a look at Jupiter. See if you can see any of its 4 bright Galilean moons or its large atmospheric belts (there are usually 2 prominent belts but 1 has recently disappeared though it may make a comeback at any time). In addition, Jupiter is within 2.9° of +5.8 magnitude Uranus on Dec 1 and 0.7° on Dec 31.

Dec 13 - First Quarter Moon 7° from Jupiter

Saturn - Saturn rises a few hours before the Sun. Located in Virgo, the ringed planet is a close match in brightness (mag +0.9) to the Spica, the brightest star in Virgo (mag +1.0). Saturn spends the entire month within 9-10° of Spica. It's rings are slowly opening up and are currently 9° from edge-on.

Dec 1 - Moon 7° from Saturn
Dec 28 - Moon 7° from Saturn

Venus - After passing through inferior conjunction in late October , Venus is now the dominant sight in the morning sky. On Dec 1, Venus rises 3 hours before the Sun in the eastern sky. By the end of the month, it is up almost 4 hours before sunrise. Unlike this year's evening apparition which was poorly placed, Venus' current stay in the morning sky will be a good one for northern observers.

Dec 2 - Venus at its brightest (magnitude -4.5 to -4.9 depending on the source)
Dec 2 - Moon 6° from Venus
Dec 31 - Moon 7° from Venus

Meteors

Meteor activity is still quite high in December. 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, 10-16 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Geminids (GEM) [Max Date = Dec 14, Max Rate = ~60-120 per hour under dark skies]

Along with the Perseids of August, the Geminids are one of the best meteor showers delivering great displays year after year. This year's Geminids are nicely timed with the First Quarter Moon will be setting around midnight.

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 night of December 13/14 though numerous meteors should be visible for a day or two on either side of the peak. 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 (though with the caveat for this year that the Moon will spoil the show until it sets around midnight). Under a dark rural moon-less sky, the Geminids can produce as many as 100+ meteors per hour. Observers under suburban skies will see lower rates.

The Geminids are the result of the break-up and subsequent activity of the "asteroid" (3200) 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.

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.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally's and Mark Davis's NAMN Notes, and the International Meteor Organization's 2010 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 - 8.0)

Comet 103P/Hartley 2 - Comet 103P/Hartley 2 continues its retreat from the Earth and Sun. Well past its late October peak in brightness, the comet starts December around magnitude 6 and should steadily fade to around magnitude 8 by the end of the month.

.103P was discovered at Siding Spring Observatory (Australia) on March 15, 1986 by  Malcolm Hartley. With an orbital period of 6.47 years, the comet's orbit currently stretches from 1.06 AU to 5.89 AU from the Sun. Though not an especially big comet, this year it passed 0.12 AU from Earth on October 21 allowing the comet to get much brighter than usual.The comet starts the month at a distance of 1.16 AU from the Sun and 0.29 AU from Earth. By mid-month it will be 1.24 AU from the Sun and 0.36 AU from Earth. At the end of the month, Hartley 2 will be 1.36 AU and 0.46 AU from the Sun and Earth, respectively. 

Even though the comet is currently 6th magnitude and theoretically bright enough to be an easy binocular object, in reality this is a difficult object to observe. With a coma diameter approaching 1° across, the light of the comet is spread over a wide area. As a result, even small amounts of light pollution renders much of the coma invisible. Dark skies are always a plus and will help in observing this challenging comet.

The comet is located in the southern part of the winter Milky Way. The start of December sees the comet in Puppis just to the south of the bright open clusters M46 and M47. By the end of the month it will have retrograded into Canis Major. It is a morning object and is visible after midnight.

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On November 4 the NASA EPOXI (ex-Deep Impact) spacecraft encountered Hartley 2 giving us close-up views of the comet's nucleus. This is the xth comet visited by a spacecraft after Comets 21P/Giacobini-Zinner (1985), 1P/Halley (1986), 19P/Borelly (2001), 81P/Wild 2 (2004), 9P/Tempel 1 (2005). On February 15, 2011, Tempel 1 will be the first comet to be re-visited by a spacecraft.

A finder chart for Comet Hartley 2 can be found at Comet Chasing and Sky and Telescope.

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 = 8.0 - 10.0)

Comet P/2010 V1 (Ikeya-Murakami) - Probably the surprise comet of the year, Comet Ikeya-Murakami is a rare visual find. Not long ago most bright comets were discovered by amateur astronomers visually through the eyepiece of their telescopes without the help of computers. Nowadays, the professional surveys are able to scan large swathes of sky and with the help of digital CCD cameras and detection software find most comets.

The reason Ikeya and Murakami could discover P/2010 V1 is probably because it is a small and usually weakly or even inactive comet. The fact that the comet was not visible to other comet hunters (including Ikeya) a day or two before discovery suggests it has recently undergone an outburst. CCD images of its rapidly expanding coma also point to a recent event. At discovery the comet was as bright as magnitude 7.5 to 8.0. At the start of this month the comet is around magnitude 9 to 10 and, baring another outburst, should quickly fade.

Another interesting thing about this comet is its orbit. With an aphelion of only ~4.2 AU, the comet does not extend far enough to reach the orbit of Jupiter. Unlike most cometary orbits, this orbit is very asteroidal and suggests that it more closely related to volatile-rich Main belt comets than the typical comet from the outer Solar System.

Perihelion occurred on 2010 Oct. 11 at 1.57 AU. The comet is now outbound and at mid-month is located 1.68 AU from the Sun and 2.21 AU from Earth. Starting the month in Virgo the comet will cross into Libra by mid-month.

A finder chart for Comet Ikeya-Murakami 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 < 9.0)

(7) Iris

Iris is an inner Main-Belt asteroid that can occassionally get as bright as any asteroid. This year, Iris will not get as bright but will still become a binocular object at opposition on January 24 at magnitude 7.9. During December, it is located in the constellation of Cancer a few degrees to the southwest of the Beehive Cluster. It starts the month at magnitude 8.9 and ends it at magnitude 8.3.

With a size of 240 x 200 x 200 km, Iris is the 5th largest stoney S-type asteroid. It was discovered in 1847 by John Russel Hind, the 1st of 10 asteroids he discovered.

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.

In the Sky This Month – October 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of October 2010.

October 2010 Highlights 
* Comet 103P/Hartley 2 is a naked eye object under very dark skies
* Jupiter dominates the eastern evening sky
* Uranus remains within 3 degrees of Jupiter all month
* Orionids meteor shower will be washed out by bright Moonlight

Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Moon - The table below lists important lunar dates for the month, including the phases of the Moon and nights of lunar-planetary and lunar-stellar conjunctions.

October 1 - Last Quarter 
October 2 - Moon 8° from Pollux 
October 3 - Moon 4° from Beehive Cluster 
October 4 - Moon 5° from Regulus
October 7 - New Moon 
October 9 - Moon 3° from Venus
October 10 - Moon 3° from Mars
October 11 - Moon 3° from Antares 
October 14 - First Quarter  
October 20 - Moon 7° from Jupiter and Uranus
October 23 - Full Moon
October 25 - Moon 1.5° from Pleiades 
October 26 - Moon 8° from Aldebaran
October 29 - Moon 8° from Pollux
October 30 - Last Quarter
October 30 - Moon 4° from Beehive Cluster

Venus – Venus starts the month very low in the SW sky at sunset. By the end of twilight it has already set. Conditions only get worse as it descends towards the Sun. By mid-month, Venus is invisible in the evening sky. After passing inferior conjunction on the 29th, Venus will rapidly climb higher in the morning sky and should be visible by early next month.

October 1 - Venus 7° S of Mars
October 9 - Moon passes within 3.4° of Venus 
October 29 - Venus at inferior conjunction

Mars – Mars continues its slow grind lower in the southwestern evening sky. At a relatively faint (for a planet anyway) magnitude of +1.5, Mars is only visible low in the SW during evening twilight.

October 1 - Mars 7° N of Venus
October 10 - Moon passes within 3° of Mars

Jupiter (and Uranus, too…) – This month the ‘King of the Planets’ is also the ‘King of the Evening Sky’. At magnitude -2.8 Jupiter is the brightest ‘star’ in the eastern evening sky. It is currently located on the Pisces/Aquarius border.

If you have a pair of binoculars or small telescope take a look at Jupiter. See if you can see any of its 4 bright Galilean moons or 2 large atmospheric belts. In addition, Jupiter is within 3° of +5.7 magnitude Uranus all month long.

October 20 - Moon within 7° of Jupiter and 6° of Uranus

Saturn – Saturn starts the month behind the Sun. By the end of the month, the +0.9 magnitude planet can be seen very low  in the eastern sky during dawn. It is currently located in Virgo and will be for the next year or so.

October 1 - Saturn at conjunction with Sun

Mercury - Mercury is rapidly dropping towards the Sun at the beginning of the month. By  the end of the first week of October it will be too close to the Sun to be seen.

October 17 - Mercury at Superior Conjunction

Meteors

Meteor activity is near a yearly maximum in October. 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, 10-16 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Orionids (ORI) [Max Date = Oct 21, Max Rate = ~20-70 per hour]

The Orionids are one of the most reliable and productive showers of the year. Another point in their favor, is their high level of activity over the course of ~5 nights or so. This gives ample opportunity to catch a few Orionid meteors. Unfortunately this year the nearly Full Moon will severely hamper watching this shower.

The meteors that make up the Orionid shower were originally released by the one comet everyone has heard of, Comet Halley. 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).

The Orionids are 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. During the last  two years rates reached 40-45 meteors per hour which is nearly half the rate observed in 2007 (70 per hour). With a bright Moon-lit sky, actual rates will be much lower making this a dificult year to see the Orionids.

The Orionids appear to come from an area in northern Orion. 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.

More can be found at earlier Orionids posting from 2008 and 2009.

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.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2010 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

Comet 103P/Hartley 2 – Comet 103P/Hartley 2 should be the comet of the year. Currently as bright as magnitude +5.5 to +6.5 magnitude, naked eye sightings of this comet have already been reported from very dark sites. The comet will continue to brighten during the course of the month.

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103P was discovered at Siding Spring Observatory (Australia) on March 15, 1986 by  Malcolm Hartley. With an orbital period of 6.47 years, the comet’s orbit currently stretches from 1.06 AU to 5.89 AU from the Sun. Though not an especially big or active comet, this year it passes 0.12 AU from Earth on October 21 allowing the comet to get much brighter than usual.

The comet starts the month at a distance of 1.12 AU from the Sun and 0.18 AU from Earth. By mid-month it has moved into Andromeda and will be 1.21 AU from the Sun and 0.29 AU from Earth. Closest approach to Earth occurs on October 21 at 0.12 AU while closest approach to the Sun happens on October 28 at 1.06 AU. At the end of the month, Hartley 2 will be 1.06 AU and 0.14 AU from the Sun and Earth, respectively.

Last month there was concern that the comet was running much fainter than expected. Due to the large diffuse nature of its coma, many observers were underestimating the brightness of the comet. The comet still appears to be a little fainter than predicted but it should still brighten to a nice magnitude +4.5 to +5.0 by the end of October.

Under very dark skies the comet can already be seen with the naked eye. For most of the rest of us, Hartley 2 is a large (30’+) diffuse fuzz ball. Under my moderately light polluted sky (LM +5.5), the comet was a difficult object in 10×50 binoculars. As always, the darker the sky the better.

The comet is traversing the winter Milky Way and starts the month in Cassiopeia before running the length of Perseus and Auriga and ending the month in Gemini. It is visible all night long at the start of the month but becomes solely a morning object by mid-month.

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In early November the NASA EPOXI (ex-Deep Impact) spacecraft will encounter the comet giving us close-up views of the comet’s nucleus.

A finder chart for Comet Hartley 2 can be found at Comet Chasing and Sky and Telescope.

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

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

None

Asteroids

Binocular and Small Telescope Asteroids (V < 9.0)

(6) Hebe and (8) Flora

These 2 large inner Main Belt asteroids will move in tandem this fall. Both are S-type asteroids with similar compositions and albedos. (6) Hebe is the larger of the pair (205 x 185 x 170 km). Recent research suggests that it is the source of many ordinary chondrite meteorites and near-Earth asteroids. (8) Flora is a little smaller (136 x 136 x 113 km) and is the largest surviving member of a numerous asteroid family created by a long ago impact.

This month Hebe is retrograding in Cetus and will fade from magnitude 7.7 to 8.4. Just across the border in Aquarius Flora fades from magnitude 8.5 to 9.1.

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 Hebe from Heavens Above.

In The Sky This Month – September 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of September 2010.

September 2010 Highlights

* Venus, Mars and Spica together in evening sky at start of month
* The above 3 joined by the Moon on the 11th
* Jupiter at opposition (21st) with Full Moon (23rd) and Uranus nearby
* Mercury has a good morning apparition
* Comet 103P/Hartley 2 is bright enough for small telescopes and binoculars

Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Moon - This month brings a new addition to the “In The Sky This Month” lineup. The table below lists important lunar dates for the month, including the phases of the Moon and nights of lunar-planetary and lunar-stellar conjunctions.

September 1 - Last Quarter
September 1 - Moon 1° South of Pleiades
September 1 - Moon 8° North of Aldebaran
September 4 - Moon 8° SSW of Pollux
September 5 - Moon 4° SSW of Beehive Cluster
September 8 - New Moon
September 9 - Moon 7° SSW of Saturn
September 10 - Moon 3° SSW of Spica
September 11 - Moon 5° SSW of Mars
September 12 - Moon 0.6° from Venus
September 14 - Moon 2° NNW of Antares
September 15 - First Quarter
September 23 - Full Moon
September 23 - Moon 7° from Jupiter
September 28 - Moon 1.5° from Pleiades
September 29 - Moon 8° North of Aldebaran

Saturn – Saturn is located low in the west during evening twilight. By month’s end the +1.0 magnitude planet will be too close to the Sun to be seen easily by most observers.

September 9 - Moon within 7° of Saturn

Mars – Mars is the second of three planets visible in the west after sundown. This month +1.5 magnitude Mars starts a few degrees to the upper right of brilliant Venus. Though the planets will slowly move apart they will stay within 7° of each other all month long.

September 11 - Moon passes within 5° of Mars

Venus – Venus is the third and by far the brightest planet visible in the early evening (at magnitude -4.6 to -4.8). For northern observers this is a poor apparition. Though the planet is at its brightest and located almost as far from the Sun as it gets, the angle between the ecliptic and the horizon results in the planet staying close to the horizon. A clear view of the WSW horizon is needed in order to see Venus (and Mars and Saturn, as well). The planet sets 1.5 hours after sunset at the start of September and less than an hour by the end of the month. See the notes in the Mars section above about seeing Mars in the vicinity of Venus.

September 1 - Venus within 1° of Spica
September 11 - Moon passes within 0.6° of Venus
September 27 - Venus at its brightest (magnitude -4.6)

Jupiter (and Uranus, too…) – This month Jupiter rules the heavens. On the 21st, the ‘King of the Planets’ will be at opposition (meaning it is located directly opposite the Sun on the sky). All month Jupiter will shine at its brightest (near magnitude -2.9). Opposition also means it will be visible all night long, rising in the evening, reaching its highest elevation around midnight and setting during dawn.

If you have a pair of binoculars or small telescope take a look at Jupiter. See if you can see any of its 4 bright Galilean moons or 2 large atmospheric belts. In addition, Jupiter is within a degree of +5.7 magnitude Uranus all month long.

September 18 - Jupiter and Uranus within 0.8° of each other
September 21 - Jupiter and Uranus at opposition
September 23 - Moon within 7 of Jupiter and 6 of Uranus

Mercury - Mercury starts the month too close to the Sun to be seen. By mid-month, it is in the midst of its best morning apparition (for northern observers).

September 19 - Mercury at Greatest Elongation West (18 from Sun)

Meteors

Meteor activity is near a yearly maximum in September. 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, 10-16 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

No major showers this month.

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.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2010 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 – 8.0)

Comet 103P/Hartley 2

If it behaves as expected, Comet 103P/Hartley 2 should be the comet of the year. Currently magnitude +11.5, the comet is predicted to reach naked eye visibility (for dark sky observers) in October/November.

103P was discovered at Siding Spring Observatory (Australia) on March 15, 1986 by  Malcolm Hartley. With an orbital period of 6.47 years, the comet’s orbit currently stretches from 1.06 AU to 5.89 AU from the Sun. Though not an especially big or active comet, this year it passes 0.12 AU from Earth on October 21 allowing the comet to get much brighter than usual.

The comet starts the month in the faint constellation of Lacerta at a distance of 1.31 AU from the Sun and 0.39 AU from Earth. By mid-month it has moved into Andromeda and will be 1.21 AU from the Sun and 0.29 AU from Earth. By month’s end, the comet will just south of the brightest star in Cassiopeia (Alpha Cas) and 1.13 AU from the Sun and 0.19 AU from Earth.

[Note: The following paragraph has been updated to reflect recent observations.]

Now that the Moon is out of the morning sky, visual observers have been able to estimate the brightness of the comet. Observations over the past few days show the comet to be around magnitude 8.5. This is very close to its predicted brightness and suggests the comet may live up to its expected maximum brightness of 5th or 6th magnitude this Oct/Nov. The comet is large and diffuse with much of its brightness contained in a large, faint outer coma. As a result, the comet may appear much fainter to observers using large telescopes or observing from bright sites. By the end of the month the comet should be around magnitude 6.5 making it an easy binocular object.

In early November the NASA EPOXI (ex-Deep Impact) spacecraft will encounter the comet giving us close-up views of the comet’s nucleus.

A finder chart for Comet Hartley 2 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 = 8.0 – 10.0)

Comet 10P/Tempel 2

’10P’ says it all. This was only the 10th comet to be observed at a 2nd apparition meaning we’ve been following this comet for a long time. Discovered by prolific German comet discoverer Ernst Wilhelm Leberecht Tempel in Marseille, France on July 4, 1873, Tempel 2 has been observed at nearly every return since then. The comet’s current orbit brings it to within 1.42 AU of the Sun on July 4 and to within 0.65 AU of Earth in late August.

The comet is currently at a brightness of 9.0 to 9.5 magnitude. This is a large diffuse object so it will be more difficult to see than your average 9th magnitude comet or deep sky object. From my moderately light polluted backyard and 12″ telescope, the comet was a difficult object and was estimated to be magnitude 10.0. From a dark site and 30×125 binoculars, the comet was much brighter (magnitude 9.5), larger and easier to see. The added brightness was probably due to the dark site allowing me to see much more of the comet’s coma.

At mid-month the comet will be 1.61 AU from the Sun and 0.67 AU from Earth. Tempel 2 is a morning object moving through the constellation of Cetus.

A finder chart for Comet Tempel 2 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 < 9.0)

(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 the other target of NASA’s Dawn spacecraft which is scheduled to visit it in 2015.

This month Ceres is an evening object moving from Ophiuchus into Saggitarius. The asteroid will start the month at magnitude 8.6 and fade to magnitude 9.0 by the end 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 Ceres from Heavens Above.

(6) Hebe and (8) Flora

These 2 large inner Main Belt asteroids will move in tandem this fall. Both are S-type asteroids with similar compositions and albedos. (6) Hebe is the larger of the pair (205 x 185 x 170 km). Recent research suggests that it is the source of many ordinary chondrite meteorites and near-Earth asteroids. (8) Flora is a little smaller (136 x 136 x 113 km) and is the largest surviving member of a numerous asteroid family created by a long ago impact.

This month Hebe is retrograding in Cetus and will brighten from magnitude 8.0 to 7.7. Just across the border in Aquarius Flora will brighten from magnitude 8.4 and peak at magnitude 8.2 in early September before fading back to 8.4 at the end 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 Hebe from Heavens Above.

Evening Planets – August 10

With all of the excitement about this week’s upcoming Perseids display, don’t forget that the early evening hours have their own celestial show.

Take a peek towards the western horizon as soon as it gets dark this evening. Use brilliant Venus to find Mars and Saturn nearby. If you have a clear view close to the horizon you might even be able to see quickly sinking Mercury.

Don’t worry if you miss the show tonight, the planets will be close together for the next week or so. In fact, the Moon will join the fun starting tomorrow night.

Celestial Triangle (+ Mercury and Vesta) – August 6

The early evening planetary show continues tonight. The celestial triangle of Venus, Mars and Saturn should be easy to spot with a good view of the western horizon. Mercury is also visible much closer to the horizon.

Fred Quintao of Brazil pointed out that the large asteroid Vesta is also visible nearby. His image from August 2 shows Vesta to the north of the Venus-Mars-Saturn triangle.

Image of the Vesta near the Venus-Mars-Saturn triangle. Image taken by Fred Quintao from Brazil on August 2, 2010. Credit: Fred Quintao.

Image of the Vesta near the Venus-Mars-Saturn triangle. Image taken by Fred Quintao from Brazil on August 2, 2010. Credit: Fred Quintao.

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For a view of tonight’s alignment see the chart below.

View of the western horizon after darkness falls on the evening of August 6, 2010. Created with Stellarium.

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For those wanting to find Vesta, the following chart is better. Vesta is too faint at magnitude +8.0 to be seen without the help of binoculars or a small telescope. Though not the biggest asteroid, Vesta is intrinsically the brightest due to a very high albedo (meaning it reflects a large fraction [42%] of the light that encounters it).

Fainter chart showing the position of asteroid (4) Vesta on the evening of August 6. Created with Stellarium.

Evening Trio of Planets

Look to the west right after dark this evening to see 3 (and maybe even 4!) planets grouped closely together. Fred Quintao (Brazil) shared his image of the 4 planets taken on August 3rd. Venus is the bright one with Mars and Saturn above and to the right and Mercury below and halfway to the horizon.

Image of Venus, Mars, Saturn and Mercury from Brazil on August 3rd. Credit and courtesy of: Fred Quintao.

Here in the northern hemisphere the ecliptic is at a shallow angle to the horizon. The Stellarium plot below shows the view for tonight. Venus is the brightest object in the sky after sunset so it should be relatively easy to find. Saturn is almost directly above Venus while Mars is further away to the upper left. If you have a clear view of the horizon and look early enough you can also glimpse Mercury.

Later this month after Saturn has sunk out of view, Venus and Mars will make another triple pairing with the bright star Spica. The brightest star in Virgo, Spica is visible to upper right of the current trio.

Star chart for the evening of August 5th. Produced with Stellarium.

In The Sky This Month – August 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of August 2010.

August 2010 Highlights

* Venus, Mars and Saturn close in on each other in the evening sky
* A 2nd trio of Venus, Mars and Spica form at the end of the month
* Perseid meteor shower visible under great conditions
* Mercury has a mediocre evening apparition in July/August (great from SH)
* Comet 10P/Tempel 2 reaches small telescope brightness in the morning 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

Venus, Mars and Saturn – Venus is the brightest “star” visible in the early evening (at magnitude -4.3 to -4.6). Low in the west it sets about 1.9 to 1.5 hours after sunset. Maximum height above the horizon was reached a few months ago. As a result, Venus will appear to sink lower in the sky every night. Still, it will be well placed for easy observing as it is at its brightest this month. If you are located south of the equator, this is a much better apparition and Venus is sitting as high above the horizon as it can get. Regardless, of where you are located it will be hard to miss brilliant -4 magnitude Venus in the west an hour or 2 after sunset.

This month Venus, Mars and Saturn form a tight trio in the early evening sky. On August 8, Venus (magnitude -4.3), Mars (magnitude +1.5) and Saturn (magnitude +1.1) are located within 4.8° of each other.

August 8 - Venus and Saturn within 2.7° of each other
August 13 - Moon passes within 4.2° of Venus, 7.3° of Saturn and 5.5° of Mars
August 19 - Venus and Mars within 1.9° of each othe

Jupiter - Jupiter once again returns to sight as a brilliant star in the east-southeast a few hours after sunset. The magnitude -2.6 planet will get brighter and better place for observing over the next few months. Last year Jupiter made a series of close approaches to Neptune. This year Jupiter will do the same for Uranus. All month long Jupiter will be located within a few degrees of Uranus.

August 27 - Moon passes within 6.7° of Jupiter

Mercury - Mercury is in the midst of a mediocre evening apparition for northern observers. The apparition is a great one for southern hemisphere observers.

August 12 - Moon passes within 2.2° of Mercury

Meteors

Meteor activity is near a yearly maximum in August. 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 August, 12-18 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Perseids (PER)

The Perseids are one of 2 showers that are worth getting up early for. This year the Moon will set early in the evening so the prime meteor watching hours will be nice and dark. Based on the their behavior in prior years a broad maximum is expected between 2010 Aug. 12, 18:30 UT and Aug. 13, 7:00 UT. There may even be a little enhancement as we pass through a dust trail ejected by the Perseids’ parent comet, Swift-Tuttle, in 441 AD at 13:19 UT on Aug. 13 (from the work of Mikhail  Maslov). An additional dust trail created in 1479 may also add a few meteors. The enhancements will be small and may only add another 10 or so meteors per hour to the expected maximum rate of 100 per hour.

These rates will only be visible for those under a very dark sky when the radiant is high in the sky. For most of us, rates will be lower due to light pollution. Still, unless you live in a bright major city, you should be able to see a few dozen meteors per hour.

The best time to look will be after about 1-2 am on the night of August 12/13. Meteors will appear to radiate from the constellation of Perseus in the northeast sky.

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.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2010 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 10P/Tempel 2

’10P’ says it all. This was only the 10th comet to be observed at a 2nd apparition meaning we’ve been following this comet for a long time. Discovered by prolific German comet discoverer Ernst Wilhelm Leberecht Tempel in Marseille, France on July 4, 1873, Tempel 2 has been observed at nearly every return since then. The comet’s current orbit brings it to within 1.42 AU of the Sun on July 4 and to within 0.65 AU of Earth in late August.

The comet is currently at a brightness of 9.0 to 9.5 magnitude. This is a large diffuse object so it will be more difficult to see than your average 9th magnitude comet or deep sky object. From my moderately light polluted backyard and 12″ telescope, the comet was a difficult object and was estimated to be magnitude 10.0. From a dark site and 30×125 binoculars, the comet was much brighter (magnitude 9.5), larger and easier to see. The added brightness was probably due to the dark site allowing me to see much more of the comet’s coma.

At mid-month the comet will be 1.49 AU from the Sun and 0.66 AU from Earth. Tempel 2 is a morning object moving from the constellation of Aquarius to Cetus.

A finder chart for Comet Tempel 2 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 < 9.0)

(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 the other target of NASA’s Dawn spacecraft which is scheduled to visit it in 2015.

This month Ceres is a month past opposition. The asteroid will start the month at magnitude 8.1 and fade to magnitude 8.6 by the end of the month. All month long it will slowly moving in the constellation Ophiuchus.

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.

(6) Hebe and (8) Flora

These 2 large inner Main Belt asteroids will move in tandem this fall. Both are S-type asteroids with similar compositions and albedos. (6) Hebe is the larger of the pair (205 x 185 x 170 km). Recent research suggests that it is the source of many ordinary chondrite meteorites and near-Earth asteroids. (8) Flora is a little smaller (136 x 136 x 113 km) and is the largest surviving member of a numerous asteroid family created by a long ago impact.

This month Hebe is retrograding in Cetus and will brighten from magnitude 8.7 to 8.0. Just across the border in Aquarius Flora will brighten from magnitude 9.2 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. Finder chart for Hebe from Heavens Above.

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