In The Sky This Month – January 2011

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of January 2011.

January 2011 Highlights
* Quadrantids Meteor Shower peaks on Jan 4
* Jupiter rules the evening sky, while...
* Venus dominates the morning sky with ...
* Mercury also in the midst of a good morning apparition

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.

Jan 1 - Moon 3° from bright star Antares
Jan 2 - Moon 4° from Mercury
Jan 4 - New Moon
Jan 10 - Moon 6° from Jupiter and Uranus
Jan 12 - First Quarter Moon
Jan 15 - Moon 1.3° from Pleiades
Jan 16 - Moon 8° from bright star Aldebaran
Jan 19 - Full Moon 9° from bright star Pollux
Jan 20 - Moon 4° from Beehive Cluster
Jan 21 - Moon 5° from bright star Regulus
Jan 25 - Moon 8° from Saturn and 3° from bright star Spica
Jan 26 - Third Quarter Moon
Jan 29 - Moon 3° from bright star Antares
Jan 30 - Moon 4° from Venus

Jupiter (and Uranus, too…) - The ‘King of the Planets’ continues his reign as the uncontested ‘King of the Evening Sky’ though fading from magnitude -2.3 to -2.2, nothing but the Moon rivals it in brightness. Located on the Pisces/Aquarius border, Jupiter is easy to find in the south as it gets dark. Jupiter then spends the rest of the evening getting lower in the southwest sky.

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 close to Uranus all month long. On Jan 4 the two are 0.5° apart.

Jan 4 - Jupiter and Uranus within 0.5° of each other
Jan 10 - Moon within 6-7° of Jupiter and Uranus

Saturn – Saturn rises during the middle of the night. Located in Virgo, the ringed planet is a close match in brightness (mag +0.7) to Spica, the brightest star in Virgo (mag +1.0). Saturn spends the entire month within 8-9° of Spica.

Jan 25 - Moon within 8° of 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 almost 3 hours before the Sun in the eastern sky. 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. Through a telescope it currently looks like a brilliant ‘half moon’.

Jan 8 - Venus at Greatest Elongation West
Jan 17 - Venus within 8° of bright star Antares
Jan 30 - Moon within 3.5° of Venus

Mercury – Mercury is in the middle of a good morning apparition all month long.

Jan 2 - Moon within 4° of Mercury
Jan 9 - Greatest Elongation West

Mars – Too close to the Sun for observation.

Meteors

Meteor activity starts to plummet in January. 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

Quadrantids (QUA) [Max Date = Jan 4, Max Rate = ~60-150 per hour under dark skies]

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 on the northern reaches of the constellation Bootes.

Another strike against observing the Quadrantids is their short duration. Most 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.

The peak time for this shower is always uncertain on the order of half a day or so and the IMO prediction calls for a peak some time between 21:00 UT on Jan 3 and 6:00 UT on Jan 4. This well placed for observers in Europe. Here in the US activity during the prime early morning hours should be rapidly tailing off.

Back in 2009 this shower put on a great show with the peak well observed from the US. Peak rates that year reached a ZHR of ~150-160. But in 2008, rates “only” reached into the 80s. With the Moon near New the sky will be dark. Who knows what we’ll get this year so we’ll just have to brave the cold and see.

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 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 January around magnitude 8-9 and should steadily fade to around magnitude 9-10 by the end 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 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 1.37 AU from the Sun and 0.47 AU from Earth. By mid-month it will be 1.49 AU from the Sun and 0.57 AU from Earth. At the end of the month, Hartley 2 will be 1.62 AU and 0.73 AU from the Sun and Earth, respectively.
The comet is located in the southern part of the winter Milky Way. Slowly moving north 103P will spend most of the month in Canis Major before crossing the border back into Monoceros near the end of the month. It is a month past opposition and is highest in the sky during the middle of the night.
 

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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.

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 8.3, brightens to 7.9 at opposition on the 24th and then fades to 8.1 at the end of the month..

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 – 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.

Oct 28/29 to Nov 5/6 Meteors and the Lack of Any ‘Hartley-ids’

The current streak of consecutive nights with a meteor detection is up to 41 now. And with no storm systems in the forecast the end of the streak is no where in sight.

Still some nights do experience clouds. Two nights ago, for example, was hampered by thin cirrus for the entire night which resulted in only half the number of expected meter detections.

The Orionids were still going strong back on Oct 28/29 but have declined to a light sprinkle. Luckily the Leonids are starting up and last night saw a total of 5 Leonids detected between the two cameras.

As mentioned in the previous Meteor posting, there has been talk in the media about a possible ‘Hartley-id’ meteor shower. These meteors would have been produced by Comet Hartley 2 which passed within 12 million miles of Earth 2 weeks ago. A quick look at my data over the past week shows no evidence of any shower radiating from the region around the constellation of Cygnus where the ‘Hartley-id’ radiant should be located. Other video meteor observers such as Chris Peterson (Colorado) and Garry Dymond (Newfoundland and Labrador) also detected no ‘Hartley-id’ activity. The lack of any observational evidence agrees with theoretical work done by Jeremie Vaubaillon which suggests that any meteors released by Hartley 2 over its past few returns would miss Earth by ~0.06 AU. This distance matches the current miss distance between the Earth’s and Hartley 2′s orbit.

Obs  Date(UT)      Time    TOT SPO NTA STA ORI ETT BCN LEO AND
SAL3 2010-11-06   11h 34m   26  14  2   2   5   -   -   3   0
ALLS 2010-11-06   11h 54m   5   2   1   0   0   -   -   2   0
SAL3 2010-11-05   11h 32m   17  11  2   0   4   -   -   0   0
ALLS 2010-11-05   12h 01m   10  7   0   0   3   -   -   0   0
SAL3 2010-11-04   11h 20m   32  19  2   4   1   4   2
ALLS 2010-11-04   12h 00m   9   5   1   0   1   0   2
SAL3 2010-11-03   11h 29m   31  15  4   5   3   1   3
ALLS 2010-11-03   11h 58m   10  8   1   0   1   0   0
SAL3 2010-11-02   10h 55m   21  12  0   5   3   0   1
ALLS 2010-11-02   11h 09m   7   4   0   0   1   1   1
SAL3 2010-11-01   11h 17m   39  20  2   4   10  1   2
ALLS 2010-11-01   11h 30m   7   4   0   0   3   0   0
SAL3 2010-10-31   10h 38m   35  20  2   4   7   1   1
SAL3 2010-10-30   09h 59m   40  20  1   4   7   1   1
ALLS 2010-10-30   10h 12m   16  9   1   0   5   0   1
SAL3 2010-10-29   11h 09m   41  21  3   4   12  0   1
ALLS 2010-10-29   11h 19m   18  10  2   0   6   0   0

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
SDG - Camera in San Diego operated by Bob Lunsford
Time - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions  
NTA - Northern Taurids
STA - Southern Taurids 
ORI - Orionids
ETT - Eta Taurids
BCN - Beta Cancrids
LEO - Leonids
AND - Andromedids

EPOXI Visits Hartley 2

This morning EPOXI, the spacecraft formerly known as Deep Impact, flew within 435 miles (700 km) of the nucleus of Comet 103P/Hartley 2. Images taken during the encounter are being downloaded from the spacecraft throughout the day. A few of the images have been released by the EPOXI team and can be found here.

The nucleus which is 1.2 miles (2 km) long and only 0.25 miles (0.4 km) wide at its narrowest section resembles a dog bone. In fact, it looks like a contact binary which is an object that consists of 2 main masses held together by gravity. The smooth narrow section being made up of fine material around the contact point. Recent observations suggest this shape may be common among comet nuclei. Comet 8P/Tuttle is known to have this shape and even 1P/Halley may be another example. This  is just conjecture on my part and much better analysis will come from the EPOXI team in the coming days.

Congratulations to the EPOXI team for a job well done not  only with the Hartley 2 flyby but also with the Tempel 1 encounter and the cruise phase extrasolar planet observations!

Close-up image of the nucleus of Comet 103P/Hartley 2 taken with the EPOXI s/c on 2010 Nov 4. Credit: NASA/EPOXI Team/JPL.

Montage of 5 images taken by the EPOXI s/c as it flew past the nucleus of 103P/Hartley 2. Credit: NASA/EPOXI Team/JPL.

In The Sky This Month – November 2010

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

November 2010 Highlights
* Comet 103P/Hartley 2 is still a naked eye object (though fading) under very dark skies
* Jupiter dominates the eastern evening sky
* Uranus remains within 3 degrees of Jupiter all month
* Venus rockets into the morning sky
* Leonids meteor shower has a weak peak on the 17th

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.

Nov 1 - Moon 5° from Regulus
Nov 4 - Moon 7° from Saturn and 3° from Spica
Nov 5 - Moon 1° from Venus (but 12° from Sun)
Nov 6 - New Moon
Nov 7 - Moon 2° from Mars
Nov 8 - Moon 3° from Antares
Nov 13 - First Quarter 
Nov 16 - Moon 7° from Jupiter and 6° from Uranus
Nov 21 - Full Moon
Nov 21 - Moon 2° from Pleiades
Nov 22 - Moon 8° from Aldebaran
Nov 25 - Moon 9° from Pollux
Nov 26 - Moon 4° from Beehive Cluster
Nov 28 - Last Quarter
Nov 28 - Moon 5° from Regulus

Mercury – Mercury pops above the southwestern horizon around mid-month for a relatively poor evening apparition for northern observers (it is a pretty good one for those south of the equator). For most of the month Mercury hangs out with Mars and Antares. At magnitude -0.4, it is much brighter than the ‘Red Planet’. This evening apparition will continue into December.

Nov 15 - Mercury, Mars and Antares can fit within a 5° circle
Nov 20 - Mars and Mercury within 2° of each other 

Mars – Mars has fun this month with conjunctions with Mercury and 1st magnitude star Antares. Unfortunately, you’ll need an ultra-flat and ultra-clear southwestern horizon to see any of this. For most of us, the current Martian apparition is over. For the next few months the planet will be on the far side of the Sun and out of view.

Nov 7 - Mars 2° from the Moon
Nov 11 - Mars 4° from Antares 
Nov 15 - Mercury, Mars and Antares can fit within a 5° circle
Nov 20 - Mars and Mercury within 2° of each other 

Jupiter (and Uranus, too…) – ‘King of the Planets’ continues his reign as the uncontested ‘King of the Evening Sky’. though fading from magnitude -2.8 to -2.6, 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 2 large atmospheric belts. In addition, Jupiter is within 3.4° of +5.8 magnitude Uranus all month long.

Nov 16 - Moon within 7° of Jupiter and 6° of Uranus

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). It’s rings are slowly opening up and are currently 9° from edge-on.

Nov 4 - Saturn within 7° of the Moon

Venus – After passing through inferior conjunction last month, Venus begins a 10-month stay in the morning sky. On Nov 1, Venus rises only a half an hour before the Sun in the eastern sky. By the middle of the month, it is up 2 hours before sunrise and 3 hours before sunrise by the end of the month. 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.

Nov 5 - Moon 1° from Venus (but 12° from Sun)

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

Leonids (ORI) [Max Date = Nov 17, Max Rate = ~10-20 per hour]

The Leonids are the only November shower which can approach major shower status. Though this shower has produced some of the greatest meteor storms in history, in most year’s it produces a rather pedestrian 10-20 meteors per hour under dark skies. Now that we are 12 years removed from the last perihelion of Comet Tempel-Tuttle, the parent comet of the Leonids, rates should be low with little likelihood of any enhanced activity.

The following summary from the IMO  2010 Meteor Calendar states: “This year is not expected to produce enhanced rates, but theoretical work by Mikhail Maslov suggested peak ZHRs of ~ 20 might occur around November 17, 15h UT instead of at the usual nodal crossing time above [Nov 17, 21:15 UT]. ZHRs from that later possible peak are likely to be ~ 10–20. The waxing gibbous Moon will not set until 2 to 3 a.m. local time on November 17 across the mid-latitude globe (later moonsets for places further north). As the Leonid radiant rises usefully only around local midnight (or indeed afterwards south of the equator), there will still be plenty of dark-sky time between moonset and the onset of morning twilight to observe whatever happens this year. The ~ 15h UT peak timing would coincide with moonless skies from the extreme east of Russia east to Alaska and places at similar longitudes on the Pacific Ocean. The ~ 21h UT timing would favour locations at comparable longitudes to central-eastern Asia, from roughly India east to Japan/western Australia. Other possible maxima are not excluded, and observers should be alert as often as conditions allow throughout the shower, in case something unexpected happens.”

The Leonids appear to radiate from a spot in the ‘sickle’ of Leo. Like many showers, the radiant does not rise till after midnight and is not well placed until after 3 am.

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 is now in retreat from the Earth and Sun. Though past peak brightness the comet starts the month only a few tenths of a magnitude fainter than at its best (around magnitude +4.7). By the end of the month the comet will have faded by a magnitude or more.

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 1.06 AU from the Sun and 0.14 AU from Earth. By mid-month it will be 1.09 AU from the Sun and 0.20 AU from Earth. At the end of the month, Hartley 2 will be 1.15 AU and 0.28 AU from the Sun and Earth, respectively.

Even though the comet is currently 4th to 5th magnitude and theoretically bright enough to be seen with the naked eye, in reality this is a difficult object to observe. With a coma diameter greater than 1° across, Under very dark skies the comet can be seen with the naked eye. For most of us under brighter skies, the comet is not visible naked eye object but is visible in small binoculars as a large (30′+) diffuse fuzz ball. Under my moderately light polluted sky (LM +5.5), the comet was a faint but easy object in 10×50 binoculars if you know exactly where to look. As always, the darker the sky the better.

The comet is still racing south along the winter Milky Way. It starts the month in southern Gemini before crossing through Canis Minor and Monoceros and ending the month in Puppis between the bright open clusters M46 and M47. It is a morning object and is highest in the sky before the start of dawn.

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On November 4 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

(6) Hebe is a S-type asteroid with dimensions 205 x 185 x 170 km. Recent research suggests that it is the source of many ordinary chondrite meteorites and near-Earth asteroids.

This month Hebe is in Cetus and will fade from magnitude 8.4 to 9.0.

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.

Oct 25/26/27/28 Meteors

In the last ‘Meteor’ post, I was all excited about getting a clear night (Oct 25/26) to catch some Orionids. I guess I spoke too soon. Even though there were no obvious clouds in all of AZ on the IR satellite image, there were clouds over Tucson. I’ve seen this before where the entire state is clear but the Tucson valley forms a cap of clouds. Luckily, the conditions have gotten better and last night (Oct 27/28) was crystal clear.

Last night marked the 33rd straight night with a meteor detection. Sure, one of those nights consisted of a single meteor between the clouds but it is still an impressive run. With no storms in the forecast, the streak still has a way to go.

The Orionids are on the downswing but still make up half of the detected meteors. This is true on both the near all-sky fireball camera as well as the deeper, smaller FOV camera. Unfortunately the Moon is still an issue for visual observers. Currently it is sitting right on top of the Orionid radiant (as well as on top of Comet Hartley 2).

Speaking of Comet Hartley 2, the possibility of seeing ‘Hartley-ids’ next week has made the mainstream news. A NASA Science News story suggests that two bright fireballs, with an apparent common origin seen on Oct. 16 from Western Ontario and Alabama, might be from Hartley 2. With Earth making its closest approach to Hartley 2′s orbit on Nov 2/3, any shower related to Hartley 2 will appear to radiate from Cygnus.

Though the current orbit of Hartley 2 does come within 0.068 AU of Earth and in the past it came even closer (~0.03 AU) that really is not close enough to expect any meteors. Most of the showers we see come much closer to Earth’s orbit. Peter Jennsiken’s book ‘Meteors and Their Parent Comets’ does show that Hartley 2 may produce ‘Hartley-ids’ staring in the 2050/2060 time frame. Even with a very low probability of any ‘Hartley-ids’ this year the IMO video network of cameras will be up and running. If there are any Hartley-ids (actually the shower will probably be named ‘???? Cygnids’ after a bright star nearest to the radiant) we should catch them.

Obs  Date(UT)      Time    TOT SPO NTA STA ORI EGE LMI OUI ETT BCN
SAL3 2010-10-28   07h 12m   35  12  2   2   17  1   0   1   0   0
ALLS 2010-10-28   11h 48m   18  6   1   0   9   1   1   0   0   0
SAL3 2010-10-27   06h 40m   40  12  2   6   11  1   2   0   2   4
ALLS 2010-10-27   11h 41m   19  7   1   0   10  1   0   0   0   0
SAL3 2010-10-26   04h 31m   18  4   1   0   11  0   0   0   1   1
ALLS 2010-10-26   04h 39m   13  4   0   0   6   0   0   1   1   1

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
SDG - Camera in San Diego operated by Bob Lunsford
Time - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions  
NTA - Northern Taurids
STA - Southern Taurids 
ORI - Orionids
EGE - Epsilon Geminids
LMI - Leonis Minorids
OUI - October Ursa Minorids
ETT - Eta Taurids
BCN - Beta Cancrids

Latest on Comet Hartley 2

Just a quick update on the status of Comet 103P/Hartley 2. This is the 3rd update on 103P (1st update on Sep.22 and 2nd update on Oct. 8). Up-to-date lightcurves and images will also be posted on a special page devoted to 103P. The 103P page can be located with the 103P tab at the top of the blog or by going here.

Summary

Comet 103P/Hartley 2 is currently in the middle of Auriga moving to the southeast at a little over 3° per day. With closest approach to Earth on Oct. 20 (0.121 AU) and closest approach to the Sun on Oct. 28 (1.059 AU), the comet is as big and bright as it will probably get for this return. Unfortunately, the bright Full Moon will make observing the comet difficult for the next week and a half. By the beginning of November the Moon will be out of the morning sky and the comet will be easily visible once again. At that time the comet should still be a large 4th magnitude fuzzball as it moves through Gemini. It should fade to magnitude ~6.0 by the end of November and magnitude 7.5 to 8.0 by the end of the year.

Finder charts can be found at Sky and Telescope.

Analysis

In the previous updates, there was concern that Comet Hartley 2 was not as bright as predicted. We have good data from the 1991 and 1997 returns which suggested that the comet’s 2010 return was running at least a magnitude fainter. There was also a question as to whether this was due to change in the intrinsic brightness of the comet or to difficulty in measuring the brightness of such a large object.

Based on the recent data (up to Oct 18), the apparent ‘faintness’ of the comet has more to do with measuring a large, low surface brightness coma than any intrinsic fading. 103P’s coma is LARGE. My most recent CCD images from Oct. 17 (see image further below) shows a coma over 70′ across (~1.2°). Other CCD observers such as Francois Kugel of France have reported coma measurements of 1° or larger. For comparison, the Moon’s average apparent diameter is 31′ so the comet appears ~2.3 times larger than the Moon. Only observers at very dark sites (lm of 6.5 or fainter) will be able to see the full extent of the coma with the naked eye or even optical aid. As a result, many visual observers (myself included) are not seeing the entire coma and have been underestimating the brightness of Hartley 2.

The brightest visual magnitude estimates are in the 4.5 to 5.0 range. Juan José González has consistently found the comet to be magnitude 5.0 or brighter over the past 2 weeks from extremely dark sites in northern Spain. My own CCD measurement from Oct. 17 was magnitude 4.6 so it’s probably safe to say the comet is currently a 4th magnitude object. If it brightens and fades at the same rate as it did in 1991 and 1997 then the comet is currently near its brightest and we can only expect another 0.1 to 0.2 magnitude brightening before perihelion. Unfortunately with the Moon now dominating the morning sky, the comet may actually appear fainter as bright moonlight washes out much of the coma.

The three lightcurves below are updates of the ones from my previous posts. Nothing has changed except for the addition of recent data (valid to Oct 18).

Lightcurve 1 : Apparent magnitude of Comet 103P versus time from perihelion. For comparison, the expected brightness of the comet (based on observations from the 1997 return) is also plotted (dashed line). Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Lightcurve 2 : Heliocentric magnitude of Comet 103P versus time from perihelion. Magnitudes are normalized to a distance of 1 AU from Earth and Sun and to o° phase angle. For comparison, visual magnitude observations from the 1991 return (dark grey boxes) and 1997 return (light grey circles) are also plotted. Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Lightcurve 3 : Heliocentric magnitude of Comet 103P versus heliocentric distance. Magnitudes are normalized to a distance of 1 AU from Earth and Sun and to o° phase angle. For comparison, visual magnitude observations from the 1991 return (dark grey boxes) and 1997 return (light grey circles) are also plotted. Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Closest approach to Earth occurred on Oct. 20 at 0.121 AU (11.25 million miles / 18 million km / ~48 lunar distances). The image below was taken a few nights earlier on Oct. 17 with a 10.6-cm refractor operated by Global-Rent-a-Scopes in New Mexico. Due to the rapid motion of the comet I was able to do a median combine on the 13 60-sec exposures and remove most of the stars. The remaining stellar signal can be seen as short fuzzy streaks. When the contrast is stretched the coma extends to a diameter of 71′. At the time the image was taken, the comet was 0.123 AU from Earth. Using these 2 bits of information we can determine the actual size of the coma at ~236,000 miles or ~378,000 km across which is roughly the distance from Earth to the Moon. Though large, the coma is mostly empty space filled with a scattering of cometary dust and gas. The nucleus responsible for producing all of this dust and gas is much, much smaller. At only ~1.2 km across, the nucleus is swamped by the glow of the coma and is not directly visible at this time (at least not at visible wavelengths, it could be directly observed at IR wavelengths).

The image (as well as those by others) shows a faint dust tail extending to the west-south-west. On the Oct. 17 image its length was just under 1°. Based on images from the 1991 return I’m surprised that we haven’t seen evidence of a long, narrow gas tail yet. [Added later: After reading Nicolas Biver’s recent posting on comets-ml, I’m of the opinion that the tail in my images is the ion tail. According to his calculations, the ion tail should be in a position angle (PA) of ~245° while the dust tail is at a PA of ~296°. The tail in the Oct. 17 image has a PA of 245° so it is an ion tail. It will be interesting to see if this tail lengthens in the coming weeks. Also to watch is the appearance of a dust trail as we pass through the orbit plane in early November.)

The next image was taken with a single-shot color CCD. The image only shows the inner coma of the comet but does a good job of representing the color and appearance of the comet in small telescopes.

Update on Comet Hartley 2

Comet Hartley 2 has now reached naked eye brightness for those lucky enough to observe from a dark site. For the rest of us the comet is actually a rather difficult object. Under any level of light pollution, the comet is nearly impossible to see with just the naked eye. At my home (Lm = +5.5) the comet is a faint, barely discernible fuzzball in 10×50 binoculars. At least the comet’s location is relatively easy to find due to the large number of bright stars available for star-hopping. Still the comet has not been an impressive sight and I’d guess that most inexperienced observers will have a hard time finding it.

For example, I just went out to catch a glimpse of the comet as it passed by the Double Cluster in Perseus. I  was rather surprised that I could not find it at first. Because it was located near a few bright stars it was swamped by their glow. The proximity to the stars also ruled out any attempt at estimating its brightness. On of these nights I need to drive out to a darker site and see how much of a difference that makes.

The reason for the difficulty in seeing the comet is twofold. One, the comet is large with recent CCD images finding the comet’s light spread over a coma 36′+ across. Two, any amount of light pollution really does a number on low surface brightness objects. Since most of us live and observe near city lights, objects like Hartley 2 can literally be lost against the bright sky.

The comet is much easier to see in CCD images and I continue to observe it with the LightBuckets 0.2-m (8″) astrograph. The two images below are from the nights of Oct. 2 and 6 UT, respectively. Due to the increasingly rapid motion of the comet I was able to median combine the 19 individual images from Oct. 6 UT in such a way as to make the stars (mostly) go away. The coma is fairly circular and there is little fine detail in the coma. A narrow dust(?) tail points just west of south (PA ~200-205) and can be traced up to 12′ from the nucleus. This is still within the outer coma so this comet does not (yet at least) display the ‘lollypop’-type appearance typical of 5th to 6th magnitude comets.

Recent visual magnitude estimates place the comet between magnitudes +5.3 and +6.5. My own visual estimate from last night (Oct. 7.22 UT) gave a magnitude of +5.9. CCD derived measurements from the LightBuckets 0.2-m come in a little fainter at +6.3. The following table presents a summary of my visual and CCD observations in ICQ .

Oct. 07.22, m1= 5.9, Diam=24' (Visual, 10x50 binoculars)
     06.27, m1= 6.3, Diam=36' (0.20-m reflector + CCD + Astrodon G filter)
     04.17, m1= 6.5, Diam=16' (Visual 10x50 binoculars)
     02.43, m1= 6.7, Diam=38' (0.20-m reflector + CCD + Astrodon G filter)
     02.30, m1= 6.5, Diam=20' (Visual 10x50 binoculars)
Sep. 25.31, m1= 7.3, Diam=23' (0.20-m reflector + CCD + Astrodon G filter)
     15.28, m1= 8.2, Diam=24' (0.20-m reflector + CCD + Astrodon G filter) 
     12.23, m1= 8.1, Diam=26' (0.20-m reflector + CCD + Astrodon G filter)
     03.33, m1= 9.8, Diam=8'.6 (0.61-m reflector + CCD + Astrodon G filter)
Aug. 05.37, m1=11.9, Diam=4'.4 (0.32-m astrograph + CCD + Astrodon G filter)
June 17.41, m1=16.8, Diam=0'.6 (0.32-m astrograph + CCD + Astrodon G filter)

As the graphs below show, the brightness trend has not changed over the past month. All but a single visual estimate has fallen below the expected brightness of the comet (based on its last well observed return in 1997). So unless we are all missing a large fraction of the coma and the comet is actually brighter than is being reported, Hartley 2 is on pace to peak at magnitude +4.5 to +5.0 in two weeks.

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.

Introducing Comet Hartley 2

The upcoming close approach of Comet Hartley 2 should be the cometary event of the year. If the comet behaves as it did during past returns, we should expect it to be a faint naked eye comet in October and November.

Officially designated Comet 103P/Hartley, it is sometimes known by its original moniker of Comet Hartley 2. A member of the Jupiter family of comets, the comet returns to perihelion once every 6.5 years. Its current orbit takes it to within 1.059 AU of the Sun (just beyond earth’s orbit) and as far out as 5.88 AU (about 60 million miles beyond Jupiter’s orbit).

103P was first seen on photographic plates obtained on 1986 March 15, 17 and 20 by Malcolm Hartley at the Siding Spring Observatory in Australia. At the time, the comet was a faint 17th magnitude object and 9 months past perihelion. At its first two predicted returns in 1991 and 1997 the comet brightened to a nice 8th magnitude object easily visible in small telescopes and binoculars. The 2004 return was poorly placed and the comet could not be seen near perihelion. The current return, the 5th observed, is easily the best. In fact, there will be no better apparitions of Hartley 2 this century.

Before 1971, the comet was located on orbits with much larger perihelia. As a result, the comet never got bright enough to be discovered. Though the comet was probably very active during the 1973, 1979 and 1985 returns, perihelion passage occurred on the other side of the Sun and out of view from Earth. Hence the reason the comet was not seen earlier. Had Malcolm Hartley not happened upon it in 1986, the comet would have undoubtedly been found in 1991.

This year Hartley 2 reaches perihelion on 2010 October 28 at a distance of 1.059 AU from the Sun. Closest approach to Earth occurs on 2010 October 20 at 0.121 AU from Earth (11.3 million miles or 18 million km). Such close approaches by comets are uncommon though 2 have occurred in the past 15 years (C/Hyakutake in 1996 at 0.102 AU and 73P/Schwassmann-Wachmann in 2006 at 0.079 AU) and 2 more are predicted over the next 5 years (45P/Honda-Mrkos-Pajdusakova in 2011 at 0.060 AU and 209P/LINEAR in 2014 at 0.056 AU).

The comet is already a nice sight in small telescopes. The 2 images below were taken by myself with an ASA 8″ astrograph operated by Light Buckets, LLC. For more on LightBuckets and how to use their fleet of 3 Rodeo, New Mexico based telescopes (also a 24″ and 14.5″) see their site at LightBuckets.com.

Many observers have reported estimates of the brightness of the comet over the past few months. Thanks to organizations like the International Comet Quarterly, Comet Observation Database and the CometObs mailing list, we are able to monitor the brightness behavior of the comet and compare it with its behavior from past returns.

The following 2 plots show the visual and CCD magnitude estimates for the current return as well as the 1991 and 1997 returns. Each is a plot of reduced heliocentric magnitude (magnitudes normalized to geocentric and heliocentric distances of 1 AU and a phase angle of 0° ). The correction to 0° was made with the comet dust phase function of Joseph Marcus. The top plot is phase-corrected heliocentric magnitude versus the log of the heliocentric distance while the next plot is versus time from perihelion.

The next plot takes a best fit of the 1997 data and converts it to the expected brightness of the comet in 2010 (after adjusting the heliocentric and geocentric distances and the phase angle). Luckily the perihelion distance in 1997 (1.032 AU) and 2010 (1.059 AU) are similar. Unfortunately the perihelion distance in 1991 was significantly smaller at 0.953 AU so it was excluded.

A quick glance at the plots show that the comet appears to be running fainter than in 1997. This was very apparent in August when the comet was almost 2 magnitudes fainter than predicted. In September it appears to have almost  “caught” up to its expected brightness. My CCD data produced magnitude of +8.1 and +8.2 on the 12th and 15th, respectively. But is this really the case? As the images earlier in the post show, this comet is very large and diffuse. My CCD images from Sept 12 and Sept 15 revealed a coma 26′ and 23′ across, respectively. The apparent shrinkage of the coma between the 2 nights may have more to do with the increasing moonlight than a real change. My CCD derived magnitudes are also running brighter than the visual estimates. Though the visual estimates are catching up with the CCD derived estimates. Most likely what is happening is that much of the very large and very low surface brightness coma is not being seen by the visual observers, and possible also not being entirely measured in the CCD images. The panel below shows how the diameter of the coma can changed just by stretching the contrast on  my Sept 15 images.

Three different contrast stretches from my Sept 15 8" LightBuckets image. Note how a change in contrast dramatically changes the apparent size of the coma. Credit: Carl Hergenrother.

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The CCD observations (and perhaps some of the visual too) are also hampered by the very dense Milky Way star field the comet is currently passing through. For my observations, I re-observed each field on a later night without the comet. The brightness of the background stars in the photometric aperture were then measured and subtracted from the earlier (comet + stars) measurement. This will only become more of a problem as the comet grows larger on the sky as its continues to approach Earth.

Based on the 1997 data, the comet should reach a peak brightness of magnitude +4.5 a few days before perihelion (last week of October). Unless all current observers are underestimating the brightness of the comet (possible but, hopefully, unlikely) the comet is running a little fainter this return. Based on this a peak brightness of magnitude +5.0 might be more realistic. Still such a large diffuse comet will not be an “easy” magnitude +5.0. Unlike this summer’s Comet C/2009 R1 (McNaught) which had a very small coma and appeared star-like to the naked eye, Hartley 2 may grow to as large as a degree across. If true, the comet will only be a naked eye object to those observing from the darkest sky. For the rest of us, the comet will be a nice, large binocular object.

I’ll post updates as well as new images here and at the Cometary Science Center/International Comet Quarterly.

As always if you’d like to share your observations and/or images with my readers, send them to <transientsky1@yahoo.com> or just leave a comment on the blog.

Resources for finding the comet include:

The 103P/Hartley page at the Cometary Science Center/International Comet Quarterly.

The 103P/Hartley page at Seiichi Yoshida’s Comet pages.

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.

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