Bright Comet : C/2011 L4 (Panstarrs) Mar. 2013!

[starfinder]

This news of a comet with a 'bright' future (peaking at around mag 0) seems very promising. However, there is a big BUT to it....

Here goes:

I think Comet C/2011 L4 (Panstarrs) would likely be mostly hidden-from-view when it is bright, unless it becomes extremely bright like the famous Comet McNaught or Comet Lovejoy did.

This is because Comet C/2011 L4 (Panstarrs) would remain very close to the Sun from the Earth's point of view for the crucial 4 weeks before and 4 weeks after its date of perihelion passage (11 March 2013).

Brightness wise, based on current magnitude estimates, it would only rise above mag 6 from around 10 Feb 2013 (4 weeks before perihelion), and then fall back below mag 6 after 10 April 2013 (4 weeks after perihelion). See the magnitude graph at Seiichi Yoshida's comet page (link below) as well as the magnitude graph further below which I've obtained from the Comet for Windows program (written by the same Seiichi Yoshida).

http://www.aerith.net/comet/catalog/2011L4/2011L4.html

Right below is a celestial chart showing the positions of the comet and the Sun from 1 Jan 2013 to end June 2013, which I've generated using The Sky6 planetarium software. Have a look at the various dates.

Taking specific points in time, based on data obtained from The Sky6 software:

- On 10 Feb 2013, the comet would be at R.A. 20hr 26m and the Sun would be at R.A. 21hr 36m (i.e. just 1 hr apart). From Singapore, the comet would rise at 6:14am and set at 6:08pm.

- On 01 Mar 2013, the comet would be at R.A. 23hr 25m and the Sun would be at R.A. 22hr 49m (i.e. just half hr apart). From Singapore, the comet would rise at 7:55am and set at 7:53pm.

- On 11 March 2013 (perihelion date), the comet would be at R.A. 00hr 26m and the Sun would be at R.A. 23hr 26m (i.e. exactly 1 hr apart). From Singapore, the comet would rise at 8:15am and set at 8:17pm; sunset would be at 7:17pm, and at that time the comet would be just 14 degrees above the horizon in the west and setting.

- On 25 Mar 2013, the comet would be at R.A. 00hr 37m and the Sun would be at R.A. 00hr 17m (i.e. very very close by). From Singapore, the comet would rise at 7:27am and set at 7:35pm.

- On 10 Apr 2013, the comet would be at R.A. 00hr 30m and the Sun would be at R.A. 01hr 16m (i.e. less than 1 hr apart). From Singapore, the comet would rise at 6:14am and set at 6:29pm.


Based on the above, one might say that the comet stays ‘irritatingly’ close to the Sun for the entire time it is brighter than mag 6, and so won’t be visible as it would be washed out by the glare of the Sun during that time.

I think the only possibility of this comet being worthwhile is if, as said above, it becomes an extremely bright sunset/sunrise comet near its perihelion date (when it would be at 0.3 AU, hardly a sungrazer since that is about 45 million km). Otherwise, us poor Earthlings won’t see much of it when it's bright.

[starfinder]

I was checking the list of 50 most recent CBETs this morning and saw that Comet C/2011 L4 (Panstarrs) is the subject of a new electronic telegram [add: CBET 3230 dated 2012 Sept 15]:
http://www.cbat.eps.harvard.edu/cbet/RecentCBETs.html.

I wonder what its about?

I hope its good news but it might be the opposite. The comet was recently reported to be around mag 9.5 but the IAU's Minor Planet Center states here that its now mag 13.9 (as at 15 Sept 2012):
http://minorplanetcenter.org/iau/lists/ ... etObs.html

Perhaps the comet has fizzled out or broken up??

[jiahao1986]

I hope its good news but it might be the opposite. The comet was recently reported to be around mag 9.5 but the IAU's Minor Planet Center states here that its now mag 13.9 (as at 15 Sept 2012):
http://minorplanetcenter.org/iau/lists/ ... etObs.html

Perhaps the comet has fizzled out or broken up??

Hi Gavin,

The MPC data suggests "N", which means the number 13.9 refers to nuclear magnitude, aka the magnitude of the stellar-shapped condensed coma, thus does not include the diffused outer layer of coma and tail. If the data suggests "T", that would refer to the total magnitude.

For the most recent visual/photographic magnitude reports, I normally visit the comet-obs Yahoo group: http://tech.groups.yahoo.com/group/CometObs/messages

The latest total visual magnitude estimation done by an Australian fellow suggests the comet currently stays at around mag 12, which matches the originally predicted light-curve. That light-curve peaks at around mag -1 next March.

Actually a month before the comet's brightness sustained at a level 2 magnitudes higher than the predicted values, however, it fell back recently. The drop in brightness may attribute to the freshness of the comet nucleus, i.e. the comet is having a first trip to the solar system, thus the nucleus has never been fully heated and activated. The outer evaporative materials may have been exhausted, leading to the fading.

Hopefully the inside of the nucleus gets fully heated up and unleash enough materials to break the rocky non-evaporative shell soon. Otherwise we may not have another McNaught.

[starfinder]

Hi Jia Hao, thanks for all the info and analysis, and the link to the comet webpage.

I must differ my interpretation to the comet expert! It's reassuring to know that the comet is probably still A-OK.

Looks like there are so many factors involved in lighting up a comet.

Sigh.... a nice comet for our tropical skies is long overdue. Even this one won't be favourable for us at the equator.

How nice it would be if NASA could send a probe to one of the big icy comets and change its path towards Earth (but not too near)! And as I was saying, shake a large bag of sand and stones out of the ISS to send us a meteor storm. But then again, all that won't really be natural, might as well watch a fireworks display.

Anyway, I hope you're right that nothing seriously 'bad' has happened to Comet Panstarrs. If someone can find out what has been reported about it in CBET 3230 please let me know. (It's now viewable to subcribers only; though just a few weeks ago the latest 50 CBETs were viewable to the general public.)

Incidentally, I tried imaging Comet Panstarrs from here in central Singapore using my LX-90 8" SCT this past Wednesday night at 8pm when it was about 35 degrees above the horizon in the SW (in Libra near its border with Centaurus). That was a rare clear night here compared to the past 2 weeks overall: thanks to the haze from Indonesia and the clouds from just about everywhere. However, the comet was not visible in the images as far as I could tell.

[Airconvent]

wow Gavin. You have been keeping track! Well, I missed McNaught even though it was around for weeks due to clouds. Hope this one burst out in full bloom and we have clear skies!

[starfinder]

An update: Comet C/2011 L4 (Panstarrs) has recently been reported at mag. 11.3, as at 2012 Sep. 18.04 UT:
http://tech.groups.yahoo.com/group/Come ... ssage/4796
This observation was made after the CBET dated 15 Sept mentioned above. Therefore, the comet is still on track for a good performance in around March 2013. Looks like Jia Hao was correct. Let's hope Comet Panstarrs would be a tasty appetiser to the main course, the cometary piece de resistance, Comet ISON, later that year!


PS: Rich/Weixing, as mentioned, could you pls merge this thread on Comet Panstarrs with an earlier one started by Jia Hao? Also, could rename the thread something like ''Comet C/2011 L4 (Panstarrs) in 2013'' as there are now two bright comets projected for 2013. Thanks!

[starfinder]

I managed to image Comet C/2011 L4 (PANSTARRS) fairly decently this morning after trying for nearly 2 weeks. Clouds, clouds, and more clouds.

Conditions were difficult as the comet is a pre-dawn object in the southeast from Singapore city. When this image was taken, the comet was 10.5 degrees above the horizon and the nearby Sun was 10.5 degrees below the horizon. The sky was generally cloudy, with both low-level and high-level clouds. The comet was in Scorpius, just below the constellation figure.

It's now reported at around only mag 8.4 (which is I think fainter than originally projected):
http://tech.groups.yahoo.com/group/Come ... ssage/4920

This comet is something of a difficult child. It's going to be quite difficult (or impossible) to see for observers in nearly areas of the world for several days to a few weeks before/after perihelion. Perihelion is just under 2 months away (on 10 March 2013).

[Gary]

Congrats and well done!

[starfinder]

Some not very good news.

Comet C/2011 L4 (PANSTARRS) has been observed this month to be dimmer than originally projected. Some have therefore revised its peak brightness downwards significantly. For example, Seiichi Yoshida has revised its predicted peak brightness downwards from around mag -1 to mag 3, see:

http://www.aerith.net/comet/weekly/current.html

This would amount to a demotion off its 'Great Comet' status. Seems that this 'difficult child' comet is going to make it even less worthwhile trying to spot it very low in the evening twilight from Singapore at perihelion, and in the week before and week after perihelion. Then again, it may surprise us then. Only way to find out is to wait and watch!

[starfinder]

There have been a lot of pessimistic predictions recently for Comet C/2011 L4 (PANSTARRS).

However, I decided to have a look at the historical records and accounts of the great Comet C/1975 V1 (West) to see whether there are similarities. The analysis is quite surprising. For Comet West, see:
http://www.cometography.com/lcomets/1975v1.html.
http://www.en.wikipedia.org/wiki/Comet_West

Comet West and Comet Panstarrs were/are both very long period comets (I think probably from the Oort Cloud), and thus both 'dynamically new' at the time. Comet West had a perihelion distance of 0.2 AU on 25 Feb 1976; Comet Panstarrs' perihelion on 10 March 2013 will be slightly further at 0.3 AU.

It is now (24 Jan 2013) 45 days (6.5 weeks) till Comet Panstarrs' perihelion. It's now reported at around only mag 7.5.

But what about Comet West? Taking info from the Cometgraphy website listed above, I've drawn up the following list:

Perihelion: 25 Feb 1976, at mag -2 or -3, seen in daylight, tail about 15 arcminutes long.

6 Dec 1975 (T-81): mag 12.5
End Dec 1975 (T-56): mag 9
Mid-Jan 1976 (T-41): mag 8 (about where we are now with Panstarrs)
Early-Feb 1976 (T-25): mag 6
13 Feb 1976 (T-12): mag 4 (first observation of tail)
19 Feb 1976 (T-6): mag 1
22 Feb 1976 (T-3): mag -1
24 Feb 1976 (T-1): mag -1.9
29 Feb 1976 (T+4): mag -1.3 to -1.8, tail 1 deg
3-4 Mar 1976 (T+7/8): mag 0, tail 10-15 deg long visual, 25 deg photographic.
9 Mar 1976 (T+13): mag 2
23 Mar 1976 (T+27): mag 4
13 Apr 1976 (T+48): mag 6

[Added: Another factor to consider in comparing Comet West and Comet Panstarrs is their distances during closest approach to Earth. For Comet West it was at 0.79 AU on 29 Feb 1976 (4 days after perihelion). For Comet Panstarrs, it would be about 40% further at 1.10 AU on 5 March 2013, 5 days before perihelion; and on 14 March 2013 which is 4 days after perihelion, the distance to Earth would be 1.134 AU
Sources: For Comet West: http://ssd.jpl.nasa.gov/?great_comets
For Comet Panstarrs: http://cometography.com/lcomets/2011l4.html and http://ssd.jpl.nasa.gov/sbdb.cgi?ID=dK1 ... 0#phys_par ]


There. Of course each comet is very different from one another, but I think Comet West could be a useful, and hopeful, comparison to Comet Panstarrs, esp noting that it too was at only mag 8 when 41 days before perihelion.

What do you think?