Here Comes the Geminids!

Tonight is one of the best nights of the year to see a meteor as the Geminid meteor shower is predicted to reach its 2014 peak. The Geminids are one of two annual showers (the other being August’s Perseids) that are almost guaranteed to produce high rates of meteors (at least one every few minutes or better).

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

How To See Them

This year the Geminids will be near peak intensity on Saturday night/Sunday morning, December 13/14. From a dark, moon-less sky, the Geminids have consistently produced peak rates of ~100 meteors per hour. According to the IMO, the Geminids reached ZHR rates of 134 per hour in 2013, 109 in 2012, 198 in 2011, 127 in 2010, 120 in 2009, 139 in 2008, 122 in 2007 and 115 in 2006. Note, these rates assume ideal observing circumstances that are rarely achieved. Dark sky observers may see rates that approach the ZHR values. Most of us observing under light polluted skies will see lower rates (perhaps much lower for city dwellers or observers watching before 10pm).

Unlike most showers that can only be observed in the early hours of the morning, the Geminids radiant rises as early as 7 pm and a good number of meteors can be seen by 10 pm. The radiant is nearly overhead at 2 am and it still well placed for the rest of the night. This year the Last Quarter Moon (located close to a brilliant Jupiter) will hinder Geminid watching after midnight. The shower can still be observed after Moonrise though fainter meteors will be washed out. It helps to keep the Moon out of your line of sight.

As the name implies, the Geminids appear to radiate from a point in the constellation of Gemini. More specifically from a point just to the north of the bright star Castor, the northern star in the Castor-Pollux pair. During the evening Geminids will be coming out of the northeast. By the middle of the night the radiant will be close to overhead and meteors will be raining down on all sides.

In general it is best not to look directly at the radiant. Meteors are easier to see by looking 30 or more degrees from the radiant (for reference 10 degrees is the width of your hand at arms length). The key is to look up and regardless of where you look you should see quite a few Geminids.

2014_Geminids

The night sky for December 13 at 11:00pm local time over Tucson. The Geminid radiant is shown as a yellow circle with Geminid meteors radiating away from it. Chart produced with Stellarium.

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Sky brightness matters when it comes to seeing most meteors and the Geminids are no exception. As always, the darker the sky the better. If you are located in a place with pitch black skies (mountaintops, middle of the desert, national parks) rates can be as high as ~100 per hour. In rural areas near small towns rates will be a bit lower and probably in the 80-90 per hour range. In the suburbs rates will vary depending on how close to a major city you are but you should expect rates of 20-50 per hour. In a major city rates will be very low though 2-10 per hour should be seen.

To increase your chance of seeing the Geminids find a spot with a clear view of the sky. Any obstructions (trees, buildings, etc.) can block some of the meteors. Also find a spot where lights (streetlights, security lights, etc.) aren’t shining in your eyes. This will allow your eyes to dark adapt and you will be able to see fainter, and more, meteors. The most important thing to remember is to get comfortable when observing. A lawn chair is perfect for reclining back and taking in the sky. Remember that it is cold this time of the year in the Northern Hemisphere so bundle up. It does not take much time, especially when relatively inactive, to start freezing.

Where They Come From

The Geminids were created by an enigmatic object named (3200) Phaethon. For starters Phaethon is an asteroid and only displayed what might be considered cometary activity for a few days in 2009. But meteor showers are created by comets and nearly all comets have orbits that carry them at least as far from the Sun as the orbit of Jupiter. Yet Phaethon only travels out to a distance of 2.4 AU, roughly half the distance to Jupiter’s orbit. Based on its orbit it is hard to call Phaethon anything but an asteroid.

Phaethon2014

Image of Geminid parent body (3200) Phaethon by Jean-Baptiste Kikwaya on 2014 November 27 with the Vatican Observatory VATT 1.8-m.

So what is Phaethon?

1) Phaethon could be a comet whose original orbit evolved into its current one after many millennia of close approaches with the inner planets. The probability of this happening is extremely low. Some models of the formation of the Geminids require the shower particles to be released over many centuries to millennia which is consistent with the behavior of a comet. Then again…

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 ices, 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. Or behind door #3…

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 ancient 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 from the stress of intense solar heating. 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 discrete event or events when Phaethon split or shed smaller pieces. 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 its discovery in 1983 it has been observed to ‘burp’. Near its perihelion, the asteroid is sometimes visible in near-Sun images taken with the STEREO spacecraft and occasionally appears to elongate as if it had a short tail and brighten. Analysis by David Jewitt and Jing Li (UCLA) found that Phaethon did release some surface particles. Due to intense heating (perihelion is 0.14 AU from the Sun or 7 times closer than the Earth is) some of the rocks on the surface may have fractured producing a cloud of dust which was knocked off the surface by solar radiation pressure. In effect, it is a rock comet. Still this event was very short-lived and produced a minimal amount of debris. So these type of events should not have been large enough to create the Geminids by themselves.

I penned a guest post on Phaethon for Dr. Dante Lauretta (PI of NASA’s OSIRIS-REx asteroid sample return mission) back in 2013. You can read it here.

Whether Phaeton is a traditional comet, a volatile-rich asteroid, an asteroid that split into pieces, or a ‘rock comet’, the result is going to be one of the best astronomical shows of the year. So go out and enjoy the show!

2014 AA impact site identified?

Sky and Telescope magazine is reporting that Peter Brown (University of Western Ontario) has made a preliminary identification of the impact site of 2014 AA, the New Year’s Earth impacting asteroid. Or more exactly, Dr. Brown has found the point where 2014 AA disintegrated in the Earth’s atmosphere.

Brown and his group used data from infrasound arrays to detect the ‘noise’ of the explosion. The location of the fireball was triangulated by measuring the time of arrival of the infrasound signal at a number of infrasound arrays around the world. This technique has been used to pinpoint the location of other large fireball events as well as the detonation of nuclear weapons. As reported by S&T, the preliminary location is at 40° west, 12° north or about 1,900 miles (3,000 km) east of Caracas, Venezuela.

The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.

The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.

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The discovery observations have also been posted at the websites of the NASA JPL NEO Project Office and the Catalina Sky Survey.

This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight "streaking" of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona
This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight “streaking” of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona

Jan 1/2 Meteors and Tonight’s Quadrantids

Tonight brings the peak of the best meteor shower you have probably never seen. The best showers of the year are almost always August’s Perseids and December’s Geminids. Number 3 and 4 are usually October’s Orionids or tonight’s shower, the Quadrantids.

The reason I say the Quads are probably the best shower you’ve never seen is two-fold. First as a northern shower, they take place in the dead of winter and only a few days after New Year’s. If the exhaustion from the Holiday’s season doesn’t keep most people inside then the cold definitely will. Also unlike most showers which have broad peaks which last a few days, the peak of the Quads is very narrow. Even if you are observing on the peak night, you can miss much of the show if you are off the peak by only 12 hours.

The International Meteor Organization predicts this year’s Quads peak to take place at ~19:30 UT on the 3rd which suggests the best viewing will be in Asia. But… predicting the peak time for this shower is always difficult so pretty much anywhere on Earth may see the best. The only way to know is to get out and look.

Bob Lunsford has posted an excellent guide to observing the Quads at the American Meteor Society (AMS) website. Please check it and the AMS (of which I am their Secretary) out.

For many years, astronomers were uncertain as to which comet caused the Quadrantids. No known comets was visible on a similar orbit even though the narrowness and strength of the meteor stream suggested it was created recently. We now know that the asteroid (196256) 2003 EH1 is the likely parent body of the Quads. Even though today it appears as nothing more than an asteroid it was a comet in the past and a rather bright one when seen in 1490. Earlier this year I observed 2003 EH1 with the Vatican Obs/Univ. of Arizona VATT 1.8-m as seen in the image below.

[I forgot to add that yesterday’s Earth impacting asteroid, 2014 AA, is not related to the Quadrantid meteor shower. The asteroid and the meteors have very different orbits and the fact that they both intersected the Earth on the same day (or two) is not only a coincidence but shows just how crowded space is with debris.]

Co-added R-band image of the Quadrantids parent body (xxx) 2003 EH1 taken on 2013 Sep. xx.xx UT with the Vatican VATT 1.8-m. Credit: Carl Hergenrother/Vatican Obs./University of Arizona.

Co-added R-band image of the Quadrantids parent body (196256) 2003 EH1 taken on 2013 Sep. 14.25 UT with the Vatican VATT 1.8-m. At the time the object showed no cometary activity. Credit: Carl Hergenrother/Vatican Obs./University of Arizona.

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Last night was another clear night in Tucson. Though 28 meteors were detected, only 2 were possible Quads. Tonight should see a huge increase in Quadrantid meteors.

Obs  Date(UT)      Time    TOT SPO ANT AHY COM DAD DLM JLE QUA
SAL  2014-01-02   12h 33m   28  23  1   0   0   0   2   0   2

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
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
AHY - Alpha Hydrids
COM - Coma Berenicids
DAD - December Alpha Draconids
DLM - December Leonis Minorids
JLE - January Leonids
QUA - Quadrantids

2014 AA – New Year’s Earth impactor

2014 has started off with fireworks! The first designated asteroid of the year, discovered only half an hour before midnight on New Year’s Eve (Tucson local time) but 6.5 hours into 2014 in Universal (or Greenwich Mean) time by Richard Kowalski of the Mount Lemmon Survey, was an Earth impactor.

Based on 7 astrometric measurements taken over the course of 70 minutes, the Minor Planet Center’s orbit has determined that 2014 AA impacted the Earth around Jan. 2.2 +/- 0.4 UT somewhere along an arc stretching from the eastern Pacific Ocean, southern Nicaragua, Costa Rica, very northern Columbia and Venezuela, a long stretch of the Atlantic Ocean and the African countries of Senegal, Gambia, Mali, Burkina Faso, Niger, Chad and Sudan. Maps of the possible impact points have been produced by Bill Gray and can be found here and here. The most likely impact point is in the Atlantic Ocean off the coast of western Africa.

With an absolute magnitude of ~30.9, 2014 AA was likely a very small asteroid with a diameter on the order of 1-5  meters. Such an object would have posed no danger to the ground though small meteorites may have survived passage through the atmosphere. If it fell in the ocean there is a good chance that no one directly witnessed it though the signature of its resulting fireball may be found in weather satellite images.

This marks the second time that an asteroid was detected in space prior to impact. The first impactor, 2008 TC3, was also found by Rich Kowalski and the Mount Lemmon 1.5-m reflector. That body was observed to fall over northern Sudan and led to the recovery of many meteorites (named Almahata Sitta). More on the fall of 2008 TC3 and Almahata Sitta can be found at this blog (here, here, here, and here), the Meteoritical Bulletin and Wikipedia.

Note, that for every small asteroid discovered before hitting the Earth (of which we’ve seen only two) there are many thousands of similar sized objects (and countless smaller ones) that go undetected until seen as brilliant fireballs or meteors. Hopefully planned upgrades to current asteroid surveys such as the Catalina Sky Survey/Mount Lemmon Survey and future surveys like ATLAS will result in more warning time for incoming asteroids.

Awesome Fireball Event in central Russia

2012 DA14 may not be on a collision course with Earth later today but a smaller asteroid was. A major fireball (and most likely also a meteorite dropping event) occurred over the city of Chelyabinsk, Russia. Chelyabinsk is a city of 1+ million people located just to the East of the Ural Mountains and just north of the Russia-Kazakhstan border.

The fireball that occurred there this morning appeared brighter than the Sun and produced a sonic boom that shattered windows causing flying glass-induced injuries to hundreds of people. A large building in town also seems to have been damaged. Though it is still uncertain if this was due to a large meteorite or the sonic boom.

An event like this happening only hours before the close flyby of the ~45-meter in diameter asteroid 2012 DA14, begs the question of whether the two are linked. It is probably unlikely that the Chelyabinsk fireball and 2012 DA14 are related. Luckily there are so many great videos of the fireball that an accurate orbit for the asteroid that caused the fireball should be easily determined.

[Update: 2012 DA14 and the Russian fireball can not be related. The radiant (the region of the sky that a DA14 or a piece of DA14 would appear to come from) of DA14 is at the very far southern declination of -81 degrees. This is the reason why DA14 is only visible from the southern hemisphere as it approaches Earth. A radiant that far south could not produce a fireball over Russia which is in the northern hemisphere. Any pieces of DA14 would only be able to impact Earth over the southern hemisphere or a few degrees north of the Equator. The fact that the Russian fireball and the 2012 DA14 close approach are happening on the same day is just a coincidence.]

Up-to-date information can be found at RT, here and here, and RMNB.

Many videos have been posted. The first 2 show the fireball itself. The last 2 are videos of the resulting contrail. What is very impressive about the last two is that the videos also caught the sonic boom. In one of the videos you can hear glass shattering in the background. Simply awesome…

2012 DA14

Remember to duck this Friday!

As any one who has been following the news lately knows, a small asteroid named 2012 DA14 will make an especially close flyby of Earth later this week. The 50-meter wide (~150-foot) asteroid will pass within 27,700 km (22,200 miles) of the Earth’s surface at 19:24 UT on February 15. At that time the asteroid will be over the Indian Ocean.

This is the closest known approach of an asteroid of this size. Such an occurrence should happen once every 40 years, on average. The reason this is the first detected close approach of its kind is because we only possessed the technology to easily discover such object over the past 10-15 years.

There is a zero probability that this object will hit the Earth this week. Its orbit is well enough known that not only will it not hit the Earth but it will also not be impacting any Earth-orbiting satellites. There is a 1-in-50,000 chance DA14 could hit the Earth in the years between 2080 and 2109, though it is likely that even these small impact probabilities will drop to zero after this week’s flyby.

More on the close approach of 2012 DA14 can be found at NASA/JPL and Sky & Telescope.

As close as this asteroid gets to Earth, it small size means it never gets very bright. It will brighten to about 7-8th magnitude at its closest which will make it an easy binocular or small telescope object. The hard part will be finding it. It will be moving as fast as nearly a degree per minute at its fastest. Not too mention being so close also means parallax will be an issue.

By the time the sun sets in the United States, it will have faded to 11th-12th magnitude. Only observers with relatively large telescopes will be able to spot DA14 by then as it recedes into the distance near the north star, Polaris.

In the Transient Sky – February 2013

February 2013 Highlights
* Not one but two comets should be naked eye brightness for SH observers (C/2011 L4 and C/2012 F6)
* Up north only comets 273P/Pons-Gambart and C/2012 T5 are bright enough for small scopes at 9th magnitude
* Comet C/2011 F1 (LINEAR) is also in range of small telescopes from the SH
* Small near-Earth asteroid 2012 DA14 passes 34,000 km from Earth on the 16th
* Mercury and Mars pass within 1/2° of each other low in the WSW evening sky on the 7th
* The Moon joins Mercury and Mars on the evenings of the 10th and 11th
* Moon occults Jupiter for observers in southern Australia
* Saturn rises before midnight
* Jupiter continues to dominate the evening sky
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

Evening Planets

Mercury -Mercury will have three good evening apparitions for Northern Hemisphere observers this year. The first takes place this month. The innermost planet is a relatively bright -1 magnitude at the start of the month. Though it slowly fades every night it rapidly ascends higher nightly in the western sky during dusk. On the 7th it passes ~0.4° from much fainter Mars. A very thin crescent Moon is located to the lower right of the duo on the evening of the 10th and to the upper right on the 11th. By the second half of the month Mercury is fading to 1st-2nd magnitude and falling back into the twilight glow.

Mars - Use Mercury and the Moon (see above) to spot Mars this month. The red planet will be all but unobservable for most observers for the next few months as it passes behind the Sun.

Jupiter – The King of the Planets dominates the evening sky being visible nearly overhead at the end of evening twilight. Jupiter is now two months past opposition. It spends the month just north of the stars of the Hyades cluster in Taurus as it fades from magnitude -2.5 to -2.3.  The Moon pays Jupiter a visit on the evenings of the 17th and 18th.

Morning Planets

Saturn – Saturn is an early morning object rising around 1:00 am at the start of the month and 11pm by the end of the month.  All month Saturn glows at magnitude +0.5 between Virgo and Libra. The Moon passes close to Saturn on the morning of the 3rd.

Venus – Venus is too close to the Sun for easy observation this month. It will be back, this time in the evening sky, this summer.

Meteors

The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers. Meteor activity is still near an annual maximum this month.

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 February mornings, 5 or so Sporadic meteors can be observed per hour from a dark moonless sky. The rate is near an annual minimum this month.

Major Meteor Showers

None this month.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are 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 International Meteor Organization’s 2012 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

C/2011 L4 (PANSTARRS)

Last month Comet PANSTARRS looked on pace to peak around magnitude -1 near its March 10th perihelion. But over the past few weeks the comet has not been brightening as quickly as hoped. As a result it is likely that the comet will be much fainter than -1 at its peak brightness and more along the lines of 2nd to 4th magnitude. The comet will still be a nice sight especially in binoculars and telescopes.

The comet was first seen by the Hawaiian based PanSTARRS asteroid survey on June 6, 2011 at a large distance of 7.9 AU from the Sun. At perihelion it will approach within 0.30 AU of the Sun. The comet is a new Oort cloud comet meaning it is making its first passage through the inner Solar System. The fact that it is a new Oort cloud comet explains its failure to brighten as quickly as first predicted. These sort of comet often appear relatively bright when far from the Sun because they still contain a large amount of very volatile ices. As the comet approaches the Sun, these ices sublimate and the comet brightens at a slower rate.

This month, the comet starts at a distance of 1.0 AU from the Sun with that distance dropping to 0.43 AU at the end of the month. A few recent observations place it at magnitude ~6.5-7.0. If it continues to brighten at its current rate it should become a naked eye object by mid-month. The comet will only be observable from the Southern Hemisphere this month as moves from the constellation of Sagittarius to Piscis Austrinus. Northern observers will have to wait till late March when the comet should be a naked eye object.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2011 L4 (PANSTARRS)
Date            RA        DEC    Delta   r   Elong    V
2013 Feb 01   19h 21m  -45d 22'  1.649 1.009   34    6.8
2013 Feb 10   20h 26m  -45d 15'  1.427 0.822   34    6.0
2013 Feb 19   21h 49m  -41d 06'  1.238 0.626   30    4.5
2013 Feb 28   23h 16m  -29d 13'  1.118 0.431   22    3.0

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

C/2012 F6 (Lemmon)

Everyone was expecting C/2011 L4 (PANSTARRS) and C/2012 S1 (ISON) to be the two naked eye comets of 2013. No one was expecting C/2012 F6 (Lemmon) to be vying for the status of naked eye comet when it was discovered by Alex Gibbs of the Mount Lemmon survey back on March 23, 2012. At that time the comet was a faint 20th-21st magnitude and 5.0 AU from the Sun. It also appeared to be an intrinsically faint comet. So faint in fact that I though it had a good chance of disintegrating near perihelion. Instead the comet has brightened at a rapid rate. If this brightening trend continues the comet may be a fine naked eye object this February through May. Perihelion will occur on March 24, 2013 at a distance of 0.73 AU from the Sun.

Over the past few days visual observers have estimated the comet at magnitude 6.2 to 6.5.

The comet is already too far south for most northern observers and the comet will continue to travel deeper into the southern sky this month. As a result, this comet will only be visible to southern observers till May.

The comet starts the month around magnitude 6.3 and will continue to rapidly brighten all month. By the end of the month the comet may be as bright as magnitude 6.0. It will be traveling through the far southern constellations of Musca, Octans, Tucana and Phoenix.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2012 F6 (Lemmon)
Date            RA        DEC    Delta   r   Elong    V
2013 Feb 01   13h 32m  -81d 08'  0.993 1.221   76    6.3
2013 Feb 10   23h 00m  -81d 07'  0.993 1.098   67    5.5
2013 Feb 19   23h 52m  -65d 58'  1.053 0.981   57    4.5
2013 Feb 28   00h 03m  -52d 43'  1.154 0.877   47    4.0

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

Comet C/2012 T5 (Bressi)

Comet Bressi was first spotted by Spacewatch observer Terry Bressi from Kitt Peak on October 14, 2012. If any of the comets in this blog post are likely to not survive perihelion, this is the one.

The comet is currently just within 1 AU of the Sun and little over 1 AU from Earth. Even after a recent outburst a week or two ago the comet is still rather faint. My observations place it at V magnitude 13.0 but this is most likely an underestimate as the observations were hampered by a very right Moon nearby and the comet’s low elevation. Visual observers place it closer to magnitude 11-12.

Comet Bressi will reach perihelion on February 24 at a distance of 0.32 AU from the Sun. It will be interesting to see if it survives. If it does it may brighten enough to be seen in small telescopes though observations will be limited to southern observers until March.

Recent observations place the comet at magnitude 10.5. If it can hold together till perihelion it should can brighten up to 8th-9th magnitude. Northern observers will only be able to follow the comet till around mid-month. After that it will solely be a southern object till next month.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2012 T5 (Bressi)
Date            RA        DEC    Delta   r   Elong    V
2013 Feb 01   23h 51m  -30d 29'  1.016 0.709   41   10.5
2013 Feb 10   23h 20m  -33d 04'  0.984 0.517   30    9.8
2013 Feb 19   22h 28m  -32d 03'  0.933 0.357   21    8.9
2013 Feb 28   21h 34m  -19d 22'  0.917 0.344   20    8.0 or Puff!

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

273P (Pons-Gambart)

On June 21, 1827, French astronomers Jean Louis Pons and Jean-Félix Adolphe Gambart discovered a comet among the stars of Cassiopeia. Both men were prolific comet finders. Pons was the most prolific discoverer of comets up until the modern era and still holds the record for most visual discoveries. A record that is unlikely to ever be broken. Between 1801 and 1827, Pons found 26 comets. Comet Pons-Gambart was his second to last comet find. Though not as prolific as Pons, Gambart is credited with 5 comet discoveries between 1822 and 1834. Comet Pons-Gambart was his 3rd find.

As the comet was already a few weeks past perihelion at discovery, it was only observed for ~1 month before it faded. Over the years, orbit computers have noticed that Pons-Gambart was on an obvious elliptical orbit and determined periods between ~45 and 65 years. The only problem was with periods that short the comet should have returned at least 2 to 4 times since 1827. Perhaps the comet was fainter now or even broke up in the intervening years to explain why it was constantly being missed.

Fast forward to this year… Robert Matson of Newport Coast, CA found evidence of an unknown comet on images taken with the SOHO spacecraft. SOHO’s SWAN imager is used to map the Lyman-α emission of the solar wind. SWAN is also very good at detecting hydrogen was dissociated water molecules released by comets. As a result, SWAN has been used to discover comets. Matson noted the presence of a comet on SWAN images from Nov. 7, 10, 11, 13 and 19. He then informed a number of observers about the new find and on Nov. 29 Terry Lovejoy of Australia found the comet.

Before the comet was even formally announed, Maik Meyer of Limburg, Germany noticed the similarities between the new SWAN/Matson comet and long-lost Comet Pons-Gambart. There is little doubt that the two are related and are probably the same object. Only problem is the 2012 observations don’t exactly match the 1827 observations assuming orbital periods of 45-65 years. A recent MPEC released by Gareth Williams of the Minor Planet Center found that the 2012 observations are consistent with a much longer period than previously assumed. It is likely that Pons-Gambart wasn’t really missed before because with a 188 year orbit this is actually its first return since 1827.

At first there was still come question as to whether the newly seen comet was Pons-Gambart and for awhile the comet was only known by its designation C/2012 V4. The Minor Planet Center has now officially announced it as 273P/Pons-Gambart.

After spending over a month too close to the Sun for observation, 273P is once again observable. This month it is a morning object traveling north from Serpens Cauda into Hercules.

Finder charts can be found at Chasing Comets.

Ephemeris for 273P/Pons-Gambart
Date            RA        DEC    Delta   r   Elong    V
2013 Feb 01   18h 30m  +05d 10'  1.636 1.132   42    9.0
2013 Feb 10   18h 22m  +10d 30'  1.538 1.243   53    9.2
2013 Feb 19   18h 10m  +16d 46'  1.432 1.359   65    9.4
2013 Feb 28   17h 54m  +24d 10'  1.331 1.477   77    9.7

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

C/2011 F1 (LINEAR)

No one has seen this comet for a few months because it has been too close to the Sun. It should be around magnitude 9-9.5 as it slowly moves away from the Sun.

The LINEAR near-Earth asteroid survey picked up this comet back on March 17, 2011 at 18th magnitude. It passed perihelion on January 8 of this year at 1.82 AU from the Sun.

It is yet another comet that can only be seen from the Southern Hemisphere this month as it moves from Sagittarius to Microscopium.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2011 F1 (LINEAR)
Date            RA        DEC    Delta   r   Elong    V
2013 Feb 01   19h 45m  -36d 01'  2.691 1.845   24    9.2
2013 Feb 10   20h 13m  -37d 51'  2.662 1.867   29    9.3
2013 Feb 19   20h 44m  -39d 26'  2.634 1.896   33    9.4
2013 Feb 28   21h 15m  -40d 44'  2.610 1.931   38    9.5

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

Asteroids

2012 DA14

On February 15th a ~50-meter asteroid will pass 34,000 km or 21,000 miles from Earth. The asteroid will appear as a fast moving star of 8th magnitude at its closest. For observers in the United States, the asteroid will already have made its closest approach when it becomes visible. As a result it will have faded to 11th magnitude by then.

I’ll post more on this object over the next week or so.

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