PANSTARRS – The Next Bright Comet?

Comet C/2011 L4 PANSTARRS photographed on May 18. Credit: Ernesto Guido, Giovanni Sostero and Nick Howes

Last June astronomers at the University of Hawaii announced they’d discovered a comet with the 1.8 meter (70.7 inch) telescope atop Mount Haleakala as part of the Panoramic Survey Telescope & Rapid Response System or Pan-STARRS. The survey’s goal is to photograph the entire sky several times a month in search of Earth-approaching comets and asteroids that could pose a danger to our planet.

At the time, Comet C/2011 L4 PANSTARRS (or PANSTARRS for short) was extremely faint and nearly as far away as the planet Saturn.

After more observations pinned down the comet’s orbit, predictions showed it would pass perihelion – its closest point to the sun – at a distance of 28 million miles on the evening of March 9, 2013. That’s close enough to vaporize a lot of cometary ice, releasing the dust needed to form a bright coma and tail.

Just how bright, no one can be certain. We all know how unpredictable comets can be; the break up and fading of Comet Elenin is just one recent example. But estimates based on the PANSTARR’s distance from the sun and Earth at the time of perihelion put it at magnitude 0 or as brilliant as Vega or Arcturus.

Comet C/2011 L4 PANSTARRS will appear in the evening sky just days after perihelion. The date shown here is March 12, 2013 about 40 minutes after sunset. The ultra-thin crescent moon will lie just five degrees to the north of the comet. Maps created with Chris Marriott's SkyMap software

Circumstances for viewing a bright comet couldn’t be better. PANSTARRS pops into the evening sky only a few days after closest approach to the sun. Moving rapidly northward, it soon becomes visible all night long from mid-northern latitudes in April.

PANSTARR's orbit is steeply inclined (84 degrees). Right now it's below the plane of the solar system (dark blue) but after perihelion next March its orbit takes it quickly above the plane (light blue). Credit: JPL/NASA

You might be wondering why I’d bother writing a blog about something happening 10 months down the road. Let’s just say I want as many amateur astronomers as possible to have the opportunity to see the comet early.

Die-hard comet observers have been photographing and observing the comet since late this winter, more than a year before perihelion. I’ll take that as a good sign that PANSTARRS is on schedule.

I sought the comet a week ago using a 15-inch reflecting telescope and was surprised at how easy it was to see. Located near the bright star Antares in Scorpius the Scorpion, I estimated the comet’s brightness at magnitude 12.5 (at discovery it was 19 — faint!). PANSTARRS was a very small but dense knot of light about 20 arc seconds in diameter with a faint star-like center. Its compact appearance is a good indicator of lots of dust activity in the comet’s nucleus – another positive sign for the coming apparition. A second look this past Saturday morning showed it smidge brighter yet.

Use this map to help you find the comet in your telescope. Antares is at left and the head of Scorpius is outlined. The comet is low in the southern sky from mid-northern latitudes. Stars shown to about 10.5 magnitude. PANSTARRS look like a very small "cottonball" with a brighter center at medium and high powers.

If you start observing now, you’ll have the pleasure of watching Comet PANSTARRS brighten and develop on its journey to perihelion and beyond. Following a comet night by night can be very rewarding, comparable to studying a species of bird to better understand and appreciate its behavior. For the moment, you’ll need a 10-inch or larger scope and dark skies but as the weeks and months advance,  it will gradually brighten.

Skywatchers in mid-northern latitudes will be able to follow PANSTARRS through early August before it’s too low to view and lost in the glow of evening twilight. Our next opportunity won’t be until next March post-perihelion. Southern hemisphere observers will fare much better with the comet high in the sky and well-placed for viewing for months to come.

To assist you in your quest, either download comet orbital elements for your favorite star charting program at the IAU Minor Planet Center site  or use the map above which shows the comet’s position around 11:30 p.m. CDT every five nights. PANSTARRS is still 325 million miles from Earth or more than halfway to Jupiter.

Comet Hartley 2 photographed by NASA's EPOXI mission. The bowling pin shaped nucleus is about 1.2 miles long. Jets of material, from ice vaporized by the sun's heat, are being ejected from the nucleus. Credit: NASA/JPL-CalTech/UMD

Returning to the question of the comet’s brightness, that may depend on whether it’s making its first or hundredth trip around the sun. On a first swingby,  exotic ices of nitrogen and carbon dioxide, long preserved in the deep freeze of the outer solar system, vaporize at great distances from the sun, making the comet appear unusually bright. If we’re not careful, we might extrapolate that behavior to the time of closest approach and predict a very bright passage. Unfortunately, once those ices are gone, the comet may have only a modest amount of water ice remaining for the sun to vaporize and not brighten as expected when closer to the sun.

Three types of orbits are possible for bodies in the solar system. Most orbit in ellipses around the sun. Credit: Oracle ThinkQuest Education Foundation

Comets that return time and again all have elliptical orbits around the sun like the planets but more stretched out or elongated. Comet PANSTARRS’ orbit appears for the moment to be nearly parabolic. A parabola is a sort of open-ended ellipse with one end near the sun and the other a return trip to infinity. Most comets on parabolic orbits come from the far edge of the solar system and have their orbits reworked by giant planets Jupiter and Saturn into very long but closed ellipses with orbital periods of hundreds of thousands to millions of years. PANSTARRS might be one of those “fresh” comets and putting on a good show now despite its distance. We’ll have to just wait and see.

47 Responses

  1. John

    Aren’t there numerous comets that have been discovered by PANSTARRS? Such comets are typically referred to with a more complete designation. I believe the one you’re talking about is C/2011 L4 (PANSTARRS).

    1. astrobob

      Hi John,
      Yes, it is C/2011 L4 PANSTARRS, the only PANSTARRS comet to date to rise to the level of amateur astronomer and public attention. I thought I had included that as a first reference, but looking back, I see I didn’t. I updated the blog appropriately. Thanks very much for bringing it to my attention.

  2. Edward M. Boll

    At this point I am being optimistic. I am thinking that a magnitude of -3 is not out of the question for perihelion.

  3. Edward M. Boll

    The British Astronomical Association has placed Panstaars at Magnitude 1110. 5 or brighter. If it is 10.5, it is not only the brightest comet but if it stays on track it could brighten 14 or 15 magnitudes yet, possibly becoming a faint daylight comet.

    1. astrobob

      Hi Edward,
      That’s correct. It’s currently about magnitude 10.5. It’s possible the comet will brighten that many magnitudes – and I hope it does! – but brightness predictions, especially for newly-discovered comets, can be off by several magnitudes or more. Seiichi Yoshida, a comet observer who maintains a regular website on current comets (, created a light curve showing C/2011 L4 (PANSTARRS) at about -1 mag. when brightest.

  4. Ellis F Wells

    How many arc seconds will the comet be in March when it is expected to be at its closest point? I have photographed several other comets with my 35 mm camera and am prepairing to buy a 10 in meade to photograph it. I fear i will not have enough field of view to see all of the comet and it’s tail. Suggestions?

    1. astrobob

      Hi Ellis,
      I can’t predict the size exactly, but would guess at least 6-15 arc minutes for the bright inner coma along with a couple-degree-long tail. It will be too big to capture the full comet in your scope, but you will be able to get nice shots of the comet’s head. A straight telephoto lens (200-300mm) might work well or better, a small, wide-field refractor or reflector. If the comet gets nice and bright with a several-degree-long tail, even a 35mm lens will make a great pic in a scenic setting.

  5. paul

    If what thay say about Planet X is true, we might not be around to see anything, or it might just add to the disruption that is comming. That ‘s if Planet X is really out their. However i will be looking forward yo seeing it.

    1. astrobob

      Hi Paul,
      No Planet X has been discovered – at least not yet. And if it is, it will be in an orbit at a great distance from Earth revolving peacefully around the sun.

  6. anon

    Hi, I have a question that’s related to photographing the comet with long exposures.

    What will the apparent angular velocity and direction (assuming 0 degrees is perpendicular to the horizon) of the sky be, for an observer in Stockholm (60 degrees north) who is looking towards the horizon in the west?

    Do you happen to have a formula or a calculator for this?

    1. astrobob

      Objects in the western sky will be moving approximately 1 degree every four minutes toward your western horizon. Did you need a specific rate and angle to the horizon for L4 PANSTARRS?

      1. anon

        Thanks for the info. I don’t think my photographs will be of such precision that it’s necessary to be aware of it, but if you have the angular data about the comet, it would be interesting to know it too…

        1. astrobob

          No problem, glad to help. If you wouldn’t mind, ask me closer to the time you’re planning your photos.

  7. Lukas

    I have some questions.. would it be better to fly to the southern hemisphere to photograph the comet before its closest approach to the sun and earth???? WIll the southern hemisphere have an advantage after the comet goes by its closest approach? Will the comet be better visable down under March 8-12????

    1. astrobob

      Yes, L4 PANSTARRS will be visible shining between 2nd magnitude (late Feb. 2013) and 1st magnitude (March 5) low in the western sky during evening twilight from places like Australia. When it reaches peak brightness a few days later, both hemispheres will have a good view. Since the comet moves quickly to the north, the view rapidly deteriorates for the southern hemisphere but improves for the northern by mid-late March.

      1. Lukas

        Thank you.. if you were to reccommend a time to go to Chile and back to Northern Hemisphere for comet observing this one what dates would u reccommend?

        1. astrobob

          I think the first week of March would be best. The comet will be brightest and higher up than during the same period in the northern hemisphere. As it slowly fades, it drops very low from Santiago (March 12 onward) but improves for the north. I’m using Duluth, Minn. for my northern hemisphere calculation. I would caution before you make any plans to keep close tabs on the comet to make sure it’s brightening as predicted or hasn’t broken apart and faded. One other thing to keep in mind – the tail may be short closer to perihelion (when you’d be in Chile) but lengthen to make a beautiful spectacle a week or more after perihelion when it’s best seen in the northern hemisphere.

  8. Lukas

    WIKIPEDIA UPDATE: An estimate from October 2012 predicts the comet may brighten to apparent magnitude -4 (roughly equivalent to Venus),[8] but previous predictions were that it would brighten to roughly magnitude 0.

  9. Hi Bob, really enjoying this website!

    I would like to go trekking and camping in the mountains (somewhere pre-Alps, about 45°N) when this comet is at its best for minimal light pollution and a massive winter backdrop 🙂 But I do not have any astro-software and it is pretty hard for me to deduce from online info what the best days will be to view this comet in the evening sky from our latitudes (by ‘best’ I mean most spectacular overall appearance, so magnitude/tail and maybe also still visible by the end of twilight). I think I can take one week off.

    Thanks a lot for your help!

    1. astrobob

      Hi Willem,
      Sounds like a great plan. The comet will be brightest very low in the western sky during the week of March 11-18. I’m going to go out on a limb and say that the tail will be short at first, but gradually becoming longer and more impressive later in the week when the comet’s further from the sun. The crescent moon appears near the L4 PANSTARRS – should be a wonderful sight – but by the 18th the moon is nearing first quarter phase and will begin to brighten the sky and cause the comet to lose contrast. I hope this helps.

  10. .James Carney

    Astro Bob, I live in Dallas Texas ,so would the week of March12th,be the best time to ask off at work???I enjoyed your site and I’ll probobaly go back to Dry Tortugas National Park to watch comet ISON

    1. astrobob

      Hi James,
      That would be Comet L4 PANSTARRS (easy to confuse since we have TWO bright comets this year. ISON comes in Nov.). Yes, that week would be a good one based on predictions.

  11. Bob Crozier

    So, this comet has been observed for a relatively long time now. Am I correct in assuming from the comments here that it is still expected to meet the expectations that have been placed upon it? I understand that it is still about 10-11 weeks from the expected big show, but so far so good?

    1. astrobob

      Hey Bob,
      Yes, so far, so good. The comet’s currently 8th magnitude and low in the southeastern sky in the morning hours as seen from southern latitudes like Australia. As far as I know, it’s still predicted to reach mag. 0 to -1. Like you, I’m most eager to catch sight of the comet again in early March.

  12. Neil Naude

    Hey Bob,

    Excellent site you have going here. Just a quick question from a total newbie to astronomy. I live in South Africa and would like to know in what constellation, from my location, will L4 PANSTARRS be when it is at its greatest magnitude early in March?

    Thanks again for a very informative site.


    1. astrobob

      Hi Neil,
      Thank you very much. L4 PANSTARRS will be in the constellation Pisces at that time. As it fades, it will move northward into Pegasus.

      1. Neil Naude

        Thank you very much for the response. Just to clarify, for my location Pisces and Pegasus will be to the east. And for the dates given for greatest magnitude of PANSTARRS they will come into view during sunrise. So will I be able to view the comet during that time?

        Excuse the many questions, but I would sure like to view this event if I can.

        Thanks again.

          1. Neil Naude

            Thank you very much indeed. Had to use Stellarium in the end to notice that Pisces is still visible for a while after sunset.

            Keep up the good work. And lets hope that L4 PANSTARRS lives up to our expectations.


          2. astrobob

            Yes, we won’t see many of Pisces dim stars in twilight but the northern half of Pegasus will be easier to spot.L4 PANSTARRS is currently mag. 8 and shows a slight tail.

  13. Jim Dire

    Hi Bob, thanks for the great info and the informative discussion. I figure at least one of the great comet possibilities of 2013 (PAN-STARRS or ISON) will provide a very stimulating display. Kind of like Hyakutake and Hale-Bopp back in the 1990s. I remember watching Hyakutake wheel around Polaris one night from my darkened living room. I also remember Ikeya-Seki from 1965 I think. ISON might be a part of the stream that produced it, or so I’ve heard.

    1. astrobob

      Hi Jim,
      Yes, it’s an interesting parallel you bring up – Hyakutake and Hale-Bopp in the mid-late ’90s and now another pair in 2013. Live long enough and you’ll see a bit of everything. I tried for Ikeya-Seki and did not see its grand turn around the sun because of clouds. I was just getting interested in astronomy at that time.

  14. Shardyn

    My latest sources put Panstarr’s magnitude at 1 to -1 in March with a very good chance of a long tail. Show of the decade perhaps?

    1. astrobob

      Hi Shardyn,
      Thanks for writing. Let’s hope so, because the latest observations and computations based on them indicate a peak now of mag. +2 to +3. I agree with you on the tail. In any event, we’ll never know for sure until we get closer to the time. Again, such is what makes comets so interesting in the first place.

    1. astrobob

      You asked at just the right time Curious. I’m writing a blog about just that topic for tomorrow. The comet will be visible a little better in the southern U.S. from March 7 to about the 12th. After that, all places in the U.S. are about equal.

  15. Soham

    Thankyu for providing this useful information. I jst want to ask cn ths commet be seen without binoculars frm parts of Rajasthan, India.???

    1. astrobob

      Hi Soham,
      If Comet Panstarrs brightens to 1st or 2nd magnitude – and it looks now like it might – it will be visible low in the western sky at dusk with the naked eye from Rajasthan.

  16. raman

    i live in india and have heard a lot bout comets , shooting stars and meteroits , but never got achance to see one . i am really very intrested to see them but unfortunately there is no information avaliable about the time and direction in india
    can u please help me bout timings

    1. astrobob

      Not sure of exact speed but comets move much faster when close to the sun and slow when far. PANSTARRS is probably in the 30-50km/sec. range (65,000-110,000 mph). The next bright comet is Comet ISON and will be visible with the naked eye sometime this October in the morning sky. It will be brightest around Thanksgiving.

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