Dec 15/16/17/18 Meteors

Meteor rates continue to be elevated. Though the Geminids are now history for 2009, a number of minor showers are displaying an impressive amount of activity. In particular, the December Leonis Minorids are producing between 10 and 25% of the nightly total. It will be interesting to see if this shower remains active over the next few days.

From Bob’s note for the night of Dec 15/16 : “There was scattered cirrus at dusk last night. Conditions were still good enough for video observations. Unfortunately conditions quickly deteriorated and thicker cirrus prevented the recording of any activity between 0400 and 0900 UT (8pm-1am PST). Conditions improved during the remainder of the morning allowing the recording of some activity before dawn arrived.”

… for the night of Dec 16/17 : “The cirrus was less widespread than yesterday. It was more prevalent during the evening hours and then cleared during the morning hours. It’s puzzling to see the dip in rates between 11-12 UT when it was mostly clear. It’s also surprising not to see any Antihelions prior to midnight, as the radiant is high in the sky.”

… and for the night of Dec 17/18 : “The cirrus clouds were back tonight with vengeance. It was mostly cloudy until 11UT (3am PST). The next hour seemed to be totally clear and then clouds interfered again the next hour. The last 46 minutes had mostly clear skies again. The new “COM’s” have been a disappointment. They are supposed to be slightly weaker than the “DLM’s” but the difference to me is striking with the “DLM’s” being the far stronger shower. Note that my first Ursid was detected tonight.”

Obs  Date(UT)      Time    TOT SPO ANT GEM HYD MON DLM DAD COM URS
TUS  2009-12-18   12h 12m   36  13  2   -   5   4   9   -   2   1
SDG  2009-12-18   11h 55m   33  23  4   -   2   1   2   -   0   1
TUS  2009-12-17   12h 12m   48  29  2   0   1   1   9   -   3   2
SDG  2009-12-17   12h 00m   64  47  4   -   4   1   7   -   1   0
TUS  2009-12-16   12h 06m   13  4   2   3   2   0   0   -   2   -
SDG  2009-12-16   11h 58m   32  23  2   2   1   1   2   1   0   -

TUS - Camera in Tucson operated by Carl Hergenrother
SDG - Camera in San Diego operated by Bob Lunsford
TotTime - 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
GEM - Geminids
HYD - Sigma Hydrids
MON - Monocerotids
DLM - December Leonis Minorids
DAD - December Alpha Draconids
COM - Coma Berenicids
URS - Ursid

Dec 13/14/15 and the Peak of the Geminids

Sunday night marked the predicted peak of this year’s Geminid meteor shower. Observers from around the world submitted observations to the International Meteor Organization. These observations showed that a possible double peak was observed on Dec 13 at ~18 UT and on Dec 14 at ~1 UT. At its best the Geminids produced ~130 meteors per hour (assuming a dark site where stars as faint as magnitude 6.5 could be seen and the radiant was overhead). The measured peak rate may change with further analysis. If the ZHR of 130 per hour holds then this year’s Geminids were pretty much as strong as predicted. Some predictions called for the peak to occur on Dec 14 at 5 UT so the actual peak was a few hours early.

The 2 graphs below are from the International Meteor Organization. The first shows the hourly rate of Geminids for the past 11 nights. The 2nd focuses on the peak of activity.

Graph of Geminid ZHR rates as determined from data submitted to the IMO. Credit: International Meteor Organization

Graph of Geminid ZHR rates centered on the time of the peak. Credit: International Meteor Organization

Here in Tucson something other than meteors was falling from the sky. The clouds and rain kept me from observing. Still I left my 2 cameras on and they were able to detect 7 meteors between the clouds. This is the 2nd year in a row that the Geminids have been clouded out for Tucson. Not too far to the south of Tucson in Hermosillo, Salvador Aguirre had better luck. On the night of the peak he observed 33 Geminids. Even better was his tally for the night before the peak when he observed 260 Geminids including 21 Geminids seen in a single 15 minute span.

Last night the sky was clear once again though Geminid activity has greatly decreased from the night before. 2010 will be another great year for the Geminids. Though the Moon will be a problem until around midnight. After that the sky will be nice and dark.

From Bob’s note for the night of Dec 14/15 : “After a week of clouds and rain the sky finally cleared. There was still a thin layer of high clouds which seemed to affect the sporadic count more than any of the showers. At 11:51:20 UT (3:51:20 am PST) a Sigma Hydrid fireball estimated at magnitude -7 was captured in the northeastern sky passing just east of the Big Dipper.”

A -7 magnitude Sigma Hydrid from Bob Lunsford camera on Dec 15 @ 11:51:20 UT. Credit: Bob Lunsford

Obs  Date(UT)      Time    TOT SPO ANT GEM HYD MON PUP DAD DLM COM
TUS  2009-12-15   12h 07m   58  23  2   18  6   0   0   1   7   1
SDG  2009-12-15   12h 00m   71  33  6   16  5   2   0   0   7   2
TUS  2009-12-14   02h 17m   7   2   1   4   0   0   0   0   0   0

TUS - Camera in Tucson operated by Carl Hergenrother
SDG - Camera in San Diego operated by Bob Lunsford
TotTime - 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
GEM - Geminids
HYD - Sigma Hydrids
MON - Monocerotids
PUP - Puppids/Velids 
DAD - December Alpha Draconids
DLM - December Leonids Minorids
COM - Coma Berenicids

Dec 11/12/13 Meteors

The Geminids peak for 2009 is now upon us. The peak is scheduled for around 5 UT tonight (Sunday night). That works out to about midnight EST and 9 pm PST. The peak is not very sharp so rates will be good all night long. In fact for western observers, there will be very few meteors observable at 9 pm because the radiant will still be low. It is better to wait till 10 or 11 before going out.

There does seem to be one big problem with tonight’s shower, the weather. Most of the country is under clouds or fog. The visible weather image below was taken at 20:15 UT and is from The National Center for Atmospheric Research (http://www.rap.ucar.edu/weather/satellite/).

Here in Tucson we have 2 storms moving through. The 1st one is here and has produced thick cloud cover. The 2nd is forecast to move through some time tonight and bring some showers with it. I’m hoping for a bit of clear patch between the storms.

Luckily the past 2 nights stayed clearer than predicted. It is obvious that the rate of Geminids have shot up recently. Based on the IMO Real ZHR page, ZHR visual rates were on the order ~40-50 last night. This means last night would have been a fine night for watching meteors. Assuming it is clear, rates for tonight will be 2-3 times greater than last night.

Obs  Date(UT)      Time    TOT SPO ANT GEM HYD MON PSU PUP DAD DLM COM
TUS  2009-12-13   11h 27m  110  13  3   83  4   5   0   0   1   1   0
TUS  2009-12-12   12h 11m   63  14  3   38  4   0   0   1   1   1   1

TUS – Camera in Tucson operated by Carl Hergenrother
SDG – Camera in San Diego operated by Bob Lunsford
TotTime – 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
GEM – Geminids
HYD – Sigma Hydrids
MON – Monocerotids
PSU – Psi Ursae Majorids
PUP – Puppids/Velids
DAD - December Alpha Draconids
DLM - December Leonids Minorids
COM – Coma Berenicids

Highlight on the Geminids

This Sunday evening/Monday morning will bring the peak the Geminids, one of the year’s better meteor showers. It’s usually a toss up as to which is better, the Perseids of August or the Geminids, though lately the Geminids have been routinely out-producing the Perseids. If the sky is clear where you live this Sunday/Monday night will provide one of the few nights of the year when it’s almost guaranteed that you will be able to observe a meteor after about 10-20 minutes of observing.

From a dark, moon-less sky, the Geminids have been known to consistently produce rates of over 100 meteors per hour at their peak. Unlike most showers that can only be observed in the early hours of the morning, the Geminids can be seen in good numbers as early as 10 pm and are great anytime after midnight. The Geminids will appear to radiate from the constellation of Gemini near the bright star Castor.

According to analysis of meteor video data by Sirko Molau, the Geminids are active for almost an entire month between the dates of November 23 and December 21. Though high rates are only possible within a few days of the peak. This year the peak is predicted for the nights of December 13/14.

The International Meteor Organization (IMO) has a “live” graph showing the rate of the Geminids as reported by visual observers around the world.

Most meteor showers are produced by comets with orbits that extend out to the orbit of Jupiter or beyond. The Geminids are different. They are on a very short uncomet-like orbit that extends from a very close 0.14 AU from the Sun to a not so far 2.40 AU.

Orbit diagram of the Geminids and their parent Phaethon. Chart is valid for Dec 13, 2009. Created with the freeware program C2A.

In 1983, the parent body of the Geminids was discovered and surprisingly it looked like an asteroid. Since its discovery, the Geminid parent (3200) Phaethon has not (or has it, more below?) shown any cometary activity. So what is it?

1) Phaethon could be a comet whose original orbit evolved into its current one after many millennia of close approaches with the inner planets. Some models of the formation of the Geminids require the shower particles to be released over many centuries to millennia. This is consistent with the behavior of a comet.

2) Phaethon may be a Main-Belt comet. Main-Belt comets are objects that originate in the outer Asteroid, or Main, Belt. Since they contain a sizable fraction of volatile material (water, carbon monoxide, etc.), they can occasionally exhibit cometary activity. Four of these objects have been observed to display cometary activity in the Main Belt. Since they start on asteroid orbits, it is not too difficult for one of them to find itself on an orbit similar to Phaethon.

3) Phaethon is an asteroid that broke up in the past. There is evidence to suggest that Phaethon is just the largest piece of a past break-up. In fact, two additional asteroids that may once have been a part of Phaethon have been found, (155140) 2005 UD and 1999 YC. According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets”, the Geminids can be explained by the break-up of Phaethon just after perihelion many orbits ago. Since Phaethon gets to within 0.14 AU (14% of the Earth-Sun distance), perhaps it split under the intense solar heat. BTW, this scenario does not rule out Phaethon as a ice-rich Main-Belt comet.

The recent discovery of additional asteroids related to Phaethon points to scenario 3 as the most likely origin of the Geminids. If true, the Geminids were not the result of long-term cometary activity like most meteor showers but were created in a single event when Phaethon split or shed a smaller piece. The Daytime Sextentids and perhaps the very minor Canis Minorids were created by even older break-up events.

Though Phaethon has behaved like an asteroid since discovery there was an event of something weird happening this summer. For a few days this July, the asteroid was visible in near-Sun images taken with the STEREO spacecraft. At the time Phaethon was near perihelion and appeared to be elongated as if it had a short tail. The asteroid also appeared to brighten at the time. Though the details are still sketchy and we await a more rigorous analysis, it is possible Phaethon released some particles for a few days. At the same time the asteroid was in the midst of a relatively dense stream of particles released emanating from the Sun (remember at the time Phaethon was only 0.14 AU from the Sun). Perhaps these particles knocked some fine regolith (science term for asteroid soil) off the surface and this sort of event is a common occurrence for objects with very small perihelia distances.

Meteor Activity Outlook for December 12-18, 2009

The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 13. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Unfortunately this year the bright moon spoils the show during the first week of the month. During the second week of December the moon will pass its last quarter phase and will not be such a nuisance .

As seen from the southern hemisphere the sporadic rates are increasing toward a January maximum. Shower rates are also good but the Geminids suffer a bit from the lower elevation seen from southern locations. Still with the warmer weather now occurring south of the equator, December is a great time to view celestial fireworks.

During this period the moon reaches its new phase on Wednesday December 16th. On that date the moon lies near the sun and cannot be seen at night. This weekend the waning crescent moon will rise during the late morning hours but will not cause any interference. The estimated total hourly rates for evening observers this week is near five as seen from the northern hemisphere and three from the southern hemisphere. For morning observers the estimated total hourly rates should be near forty from the northern hemisphere and twenty as seen from the southern hemisphere. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning December 12/13. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week.

Antihelions (ANT)

Now that the activity from particles produced by comet 2P/Encke has ceased encountering the Earth, the Taurid showers for 2009 are over and we resume reporting activity from the Antihelion radiant. This is not a true radiant but rather activity caused by the Earth’s motion through space. As the Earth revolves around the sun it encounters particles orbiting in a pro-grade motion that are approaching their perihelion point. They all appear to be radiating from an area near the opposition point of the sun, hence the name Antihelion. These were once recorded as separate showers throughout the year but it is now suggested to bin them into their category separate from true showers and sporadics. This radiant is a very large oval some thirty degrees wide by fifteen degrees high. Activity from this radiant can appear from more than one constellation. The position listed here is for the center of the radiant which is currently located at 06:16 (094) +23. This position lies in western Gemini near the fourth magnitude star Eta Geminorum. Antihelion activity may also appear from eastern Taurus, northeastern Orion, or southern Auriga. This radiant is best placed near 0100 local standard time (LST) when it lies on the meridian and is highest in the sky. Rates at this time should be ~3 per hour as seen from the northern hemisphere and ~2 per hour from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow speed.

Monocerotids (MON)

The Monocerotids (MON) are active from a radiant located at 06:52 (103) +07. This position lies in northwestern Monoceros halfway between the bright stars Betelgeuse (Alpha Orionis) and Procyon (Alpha Canis Minoris). This shower peaked on December 8, so activity is waning. Current rates would most likely average < 1 per hour no matter your location. The Monocerotids are best seen near 0100 LST when the radiant lies highest above the horizon. At 41 km/sec. the Monocerotids produce mostly meteors of medium velocity.

Geminids (GEM)

The Geminids (GEM) are active from a radiant located at 07:33 (113) +32. This position lies in northern Gemini near the fourth magnitude star Rho Geminorum. Although Geminid meteors can be seen all night long, they are best seen near 0200 LST when the radiant lies highest above the horizon. This shower is expected to peak Sunday and Monday December 13/14 when rates can surpass 60 shower members per hour as seen from dark sites. Geminid activity can be seen from the southern hemisphere but at at much reduced rate. As seen from south of the equator, Geminid activity could only be seen for a few hours before and after 0200 LST. At 35 km/sec. the Geminids produce mostly meteors of medium velocity.

Puppids-Velids (PUP)

The Puppid-Velids (PUP) are a vast complex of weak radiants located in the constellations of Puppis and Vela. Visual plots and photographic studies have revealed many radiants in this area during November and December. The combined strength of these radiants can produce a ZHR of 10. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. The center of this activity is currently located at 08:26 (126) -45. This position lies in western Vela, five degrees northeast of the second magnitude star Gamma Velorum. Peak rates occurred near December 7 so current activity is waning. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Observers located in the Southern Hemisphere have an advantage viewing this shower as the radiant will rise higher into their sky allowing more activity to be seen. At 40 km/sec. the Puppid-Velids produce meteors of medium velocity.

Sigma Hydrids (HYD)

The Sigma Hydrids (HYD) are active from a radiant located at 08:42 (130) +01. This position lies in western Hydra, just below the group of fourth magnitude stars that make up the “head” of the water serpent. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates would be ~1 per hour no matter your location. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.

December Leonis Minorids (DLM)

The December Leonis Minorids (DLM) are active from a radiant located at 10:22 (155) +34. This position lies in central Leo Minor, approximately ten degrees north of the third magnitude star Zeta Leonis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 20th so current rates would be ~1 per hour as seen from the northern hemisphere and < 1 per hour as seen from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

Coma Berenicids (COM)

Activity from the Coma Berenicids (COM) has just begun for 2009. The radiant is located at 11:30 (173) +18. This position actually lies in eastern Leo, five degrees northwest of the second magnitude star Denebola (Beta Leonis). These meteors are best seen near 0600 LST when the radiant lies highest above the horizon. This shower peaks on December 16th so current rates would be ~1 per hour no matter your location. At 65 km/sec. the Coma Berenicids produce mostly swift meteors.

December Alpha Draconids (DAD)

Lastly, the December Alpha Draconids (DAD) are active from a radiant located at 14:00 (210) +58. This position actually lies in northeastern Ursa Major, six degrees northeast of the second magnitude double star Mizar (Zeta Ursae Majoris). These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is near the end of its activity period so expected rates would be < 1 no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see ~16 Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be ~3 per hour. As seen from the mid-southern hemisphere (45S), morning rates would be ~10 per hour as seen from rural observing sites and ~2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning but may be used all week long.

Shower Name                RA     DEC   Vel     Rates
                                        km/s   NH    SH
ANT Antihelions          06h 16m  +23    30     3     2
MON Monocerotids         06h 52m  +07    41    <1    <1
GEM Geminids             07h 33m  +32    35    60    20
PUP Puppids-Velids       08h 26m  -45    40    <1     2
HYD Sigma Hydrids        08h 42m  +01    61     1     1
DLE Dec Leonis Minorids  10h 22m  +34    64     1    <1
COM Coma Berenicids      11h 30m  +18    65     1     1
DAD Dec Alpha Draconids  14h 00m  +58    44    <1    <1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a
        dark site
NH - Northern Hemisphere
SH - Southern Hemisphere

Dec 10/11 Meteors

Lots of bright meteors last night… The Geminids are really ramping up nicely with rates that appear to be twice as high as the previous night. One great thing about the Geminids is that they are visible during most of the night. Unlike most showers which can only be seen during the morning hours, GEMs can be seen within a few hours of sunset.

With the peak scheduled for Sunday night, we are at T-2 nights and counting. Unfortunately for me, the weather forecast still looks horrible for Tucson.

Bob’ notes for the night of Dec 9/10 : “Skies were mostly clear with only thin cirrus during the evening hours. Lower clouds from an approaching front interfered during the morning hours and eventually forced a premature end to the session. The Puppid-Velids and Monocerotids were unusually active tonight.”

Obs  Date(UT)      Time    TOT SPO ANT GEM HYD MON PSU PUP DAD DLM
TUS  2009-12-11   10h 53m   59  20  3   22  4   4   0   1   1   3
SDG  2009-12-11   09h 55m   26  6   1   12  0   4   0   3   0   0

TUS – Camera in Tucson operated by Carl Hergenrother
SDG – Camera in San Diego operated by Bob Lunsford
TotTime – 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
GEM – Geminids
HYD – Sigma Hydrids
MON – Monocerotids
PSU – Psi Ursae Majorids
PUP – Puppids/Velids
DAD - December Alpha Draconids
DLM - December Leonids Minorids

Dec 6/7 to 9/10 Meteors

After a few days of clouds, a little rain (0.2″ ) and a soggy camera lens, my system was back up and running last night. The soggy lens is still drying out. In the meantime, I had to buy a new (used) lens which made its debut last night.

The big story this week is the build-up in the activity level of the Geminids. Peak activity will be this Sunday night/Monday morning.

Bob’ notes for the night of Dec 9/10 : “After nearly a week of clouds and rain, the sky cleared today. It was short-lived though as high clouds moved in during the night. The evening hours were mostly clear but the more active morning hours were mostly cloudy. I still managed to record 31 meteors, 9 of them belonging to the Geminid shower.”

Obs  Date(UT)      Time    TOT SPO ANT NTA GEM HYD MON KDR PHO PSU PUP DAD DLM
TUS  2009-12-10   10h 58m   37  7   3   -   13  6   2   -   -   3   0   0   3
SDG  2009-12-10   11h 49m   31  14  -   4   9   2   -   -   0   0   1   1   -
TUS  2009-12-09   02h 41m   1   1   0   -   0   0   -   0   0   0   0   -   0
TUS  2009-12-06   08h 19m   27  6   4   -   3   8   -   1   0   0   1   -   3

TUS – Camera in Tucson operated by Carl Hergenrother
SDG – Camera in San Diego operated by Bob Lunsford
TotTime – 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
GEM – Geminids
HYD – Sigma Hydrids
MON – Monocerotids
KDR – Kappa Draconids
PHO – December Phoenicids
PSU – Psi Ursae Majorids
PUP – Puppids/Velids
DAD - December Alpha Draconids
DLM - December Leonids Minorids

In the Sky This Month – December 2009

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of December 2009. Jupiter continues its reign as not only king of the planets but king of the evening sky. Though not visible until about 10pm or so, Mars will start to contest Jupiter’s reign this month. December also brings the Geminids which are one of the best meteor showers of the year.

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

Planets

Mercury - Mercury will be an evening object this month. Though not a great apparition for northern observers, it should be easy to see if you have an unobstructed view of the southwestern horizon. The best time to see Mercury will be when the Moon passes near it on during the evenings of Dec 17 and 18. At that time Mercury will be magnitude -0.5. By the end of the month, it will be rapidly fading and getting closer to the Sun.

Dec 18 - Moon within 1.3° of Mercury

Jupiter - Jupiter continues to dominate the early evening sky. At magnitude -2.2, Jupiter is ~10 times brighter than the brightest stars in the sky this month. Of all the planets, only Venus, and on very rare occasions Mars, are brighter.

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

Dec 21 - Moon passes 4° from Jupiter
Dec 21 - Jupiter passes 0.5° from Neptune

Neptune – For those with a telescope or binoculars and a dark sky, Neptune is located within a few degrees of Jupiter. This month Jupiter and Neptune will experience the 3rd of this year’s triple conjunction as they pass ~0.5° from each other on the night of Dec 20/21. For most of the month, the 2 planets will be very close to each other and within the same field of view of most small telescopes and binoculars. This is a great opportunity to use the easy-to-find Jupiter to help locate the usually hard-to-find Neptune. Jupiter will be a bright magnitude -2.2 while Neptune will be a faint +8.0. Even Jupiter’s 4 large Galilean moons are about a dozen times brighter than Neptune even though they are much smaller. The big reason for the faintness of Neptune is its distance from both the Earth and Sun. It is roughly 6 times further away from us and the Sun as Jupiter. The distance also explains its apparent small size of 2.3″. A good sized telescope will be required to see Neptune as anything other than a faint star.

Dec 21 - Jupiter passes 0.5° from Neptune

Uranus – Uranus is located in western Pisces and is bright enough to be seen in small binoculars at magnitude +5.9 but will still require a telescope in order to see it as anything other than a star (it’s disk is only 3.5″ across).

Mars – Mars can be seen rising in the eastern sky late in the evening (~9:30 pm at the start of the month and ~8 pm at the end of the month). Mars is rapidly brightening and will double in brightness this month as it rises from +0.0 to -0.7 magnitude. By the end of the month, Mars will be brighter than all stars expect Sirius and far southern Canopus. Mars will continue to brighten to a max of magnitude -1.3 at its opposition on Jan 29 of next year. This month Mars will appear roughly stationary as it starts its retrograde motion near the Leo/Cancer border.

Dec 6 - Moon passes close (5°) to Mars

Saturn – Saturn is easy to observe during the last few hours of the night. Located in Virgo at magnitude +0.9, Virgo only rises right before the start of dawn. Telescope users should note that Saturn’s rings are still close to edge-on.

Dec 10 - Moon and Saturn within 7° of each other

Venus - Venus will be too close to the Sun this month for most observers. Some with unobstructed views of the southeastern horizon may catch a glimpse of Venus rising 30-50 minutes or so before sunrise.

Dec 15 - Venus and Moon within 3° of each other

Meteors

December hosts one of the best showers of the year in the Geminids. In addition, the background rate of meteors is still rather high. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During December, 10 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Geminids (GEM)

Along with the Perseids of August, the Geminids are one of the best meteor showers delivering great displays year after year. This year’s Geminids are perfectly timed as the Moon will be nearly New and will not spoil the show.

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. 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” 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.

Ursids (URS)

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

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 2008 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

Comet C/2007 Q3 (Siding Spring)

This long-period was first seen on 2007 August 25 by Donna Barton of the Siding Spring Survey in Australia. This past Oct. 7th the comet reached a rather distant perihelion at 2.25 AU from the Sun. Unfortunately, the comet and Earth are located on opposite sides of the Sun so the comet is rather far from Earth. Still the comet is observable in the early morning hours as a ~9.0 to 9.5 magnitude comet in Coma Berenices. At mid-month the comet is 2.38 AU from the Sun and 2.43 AU from Earth.

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

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

Comet 88P/Howell

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

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

This year perihelion occurred on Oct 12 so the comet is currently moving away from the Sun and should be fading. A day after perihelion I observed the comet from Tucson with a 12″ dobsonian. The comet was very difficult to observe from the city. At the time, I estimated its brightness at magnitude 8.5. The comet should be a fainter (95 mag or fainter) this month. The comet is located low in the southwest sky after dusk and will spend the monthcrossing Capricornus. At mid-month P/Howell will be 1.53 AU from the Sun and 2.02 AU from Earth.

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

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

Asteroids

Binocular and Small Telescope Asteroids (V < 9.0)

(4) Vesta

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

Vesta is once again observable in the morning sky before the start of dawn. It is brightening from magnitude 7.7 to 7.2 as it travels just north of Regulus in Leo.

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

Dec 2/3/4/5 Meteors

Every night seems to see at least one minor meteor show come and go. It’s been a little hard to keep up with them. Most of the showers are very minor, perhaps producing a meteor per hour at most. The majority of them have only been identified in the past few years in video and radar data.

The most important shower to become active over the past few nights is the Geminids. Though this shower is currently only producing a meteor or two per hour activity will pick up next week. By the time the shower peaks on the night of December 13/14 it will be producing between 100 and 150 meteors per hour for observers under dark skies.

It looks like the rains are finally coming to the southwest US. The forecast is for a series of storms to hit the area next week. Hopefully it will be clear for the Geminid peak. Speaking of rain, my zenith pointing camera is still out of commission due to condensation in its lens. I have ordered a new lens which will hopefully show up sometime this week.

Bob’ notes for the night of Dec 3/4 : “After two nights of clouds, the skies cleared enough for video observations. The bright gibbous moon and hazy conditions were not ideal. It was surprising that no northern Taurids were recorded tonight. Even though they are near the end of their activity period, the antihelion meteors included in the NTA count should have amounted to something.”

… for the night of Dec 4/5 : “Several layers of clouds moved in overnight greatly reducing the number of meteors recorded.

Obs  Date(UT)      Time    TOT SPO ANT NTA HYD NOO KDR PHO PSU PUP GEM DAD DLM
TUS  2009-12-05   11h 16m   15  6   0   -   3   2   0   0   1   1   2   -   0
SDG  2009-12-05   11h 49m   9   5   -   1   0   0   -   0   0   0   2   0   1
TUS  2009-12-04   12h 01m   19  9   1   -   4   2   0   0   1   1   2   -   -
SDG  2009-12-04   11h 53m   36  26  -   0   4   2   -   0   0   1   1   2   -
TUS  2009-12-03   12h 05m   10  6   0   -   3   1   0   0   0   0   -   -   -

TUS – Camera in Tucson operated by Carl Hergenrother
SDG – Camera in San Diego operated by Bob Lunsford
TotTime – 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
HYD – Sigma Hydrids
NOO – November Orionids
KDR – Kappa Draconids
PHO – December Phoenicids
PSU – Psi Ursae Majorids
PUP – Puppids/Velids
GEM – Geminids
DAD – December Alpha Draconids
DLM – December Leonids Minorids

Meteor Activity Outlook for December 5-11, 2009

The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 13. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Unfortunately this year the bright moon spoils the show during the first week of the month. During the second week of December the moon will pass its last quarter phase and will not be such a nuisance .

As seen from the southern hemisphere the sporadic rates are increasing toward a January maximum. Shower rates are also good but the  Geminids suffer a bit from the lower elevation seen from southern locations. Still with the warmer weather now occurring south of the equator, December is a great time to view celestial fireworks.

During this period the moon reaches its last quarter phase on Wednesday December 9th. On that date the moon lies ninety degrees west of the sun and rises near midnight local standard time (LST). This weekend the waning gibbous moon will rise during the evening hours and remain in the sky the remainder of the night. The bright glare from the gibbous moon will make it difficult to view any meteor activity. Once the moon passes its last quarter phase the moonlight becomes less of a problem. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and two from the southern hemisphere. For morning observers the estimated total hourly rates should be near ten from the northern hemisphere and seven as seen from the southern hemisphere. The actual rates will also depend on factors such as
personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Morning rates are reduced during this period due to moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning December 5/6. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week. The full descriptions of each active meteor shower will continue next week when
the moon becomes less of a nuisance to observers.

The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning but may be used all week long.

Shower Name                RA     DEC   Vel     Rates
                                        km/s   NH    SH
PHO Phoenicids           01h 12m  -53    18    <1    <1
NTA Northern Taurids     05h 16m  +26    29     2     1
MON Monocerotids         06h 32m  +08    41    <1    <1
GEM Geminids             07h 10m  +33    35     2    <1
PUP Puppids-Velids       08h 10m  -45    40    <1    <1
HYD Sigma Hydrids        08h 16m  +03    61    <1    <1
PSU Psi Ursae Majorids   11h 19m  +43    61    <1    <1
DAD Alpha Draconids      13h 34m  +60    44    <1    <1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a
        dark site
NH - Northern Hemisphere
SH - Southern Hemisphere