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Comet C/2011 L4 (PANSTARRS)

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#1 droid

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Posted 28 December 2012 - 07:13 PM

I just read that Comet C/2011 L4 (PANSTARRS) will be brightest in the March evening sky perhaps 2nd magnitude or better?
With that only being three or so months away, is it visible now in a small telescope or binoculars????

#2 RobK

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Posted 28 December 2012 - 08:31 PM

I just read that Comet C/2011 L4 (PANSTARRS) will be brightest in the March evening sky perhaps 2nd magnitude or better?
With that only being three or so months away, is it visible now in a small telescope or binoculars????


At present it's a southern object only but it has been picked up again after its flirtation with daylight, brightening nicely. I photographed it in twilight on 18 Dec and there have been two observations posted which average out at around mag 9 or a touch brighter. Northern hemisphere observers will have to wait until March 2013 to see it assuming all goes well, but you'll get the best of it! In the south, we will see it until mid-February only, but quite low in the sky. Bright moonlight is currently washing it out visually.

FWIW, here's a link to my image, just a dot!
http://i727.photobuc...012smsttext.jpg

Cheers -

Rob

#3 BrooksObs

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Posted 28 December 2012 - 09:52 PM

Just as Rob indicates, Comet PANSTARRS is currently a Southern Hemisphere object only, soon to be lost in the twilight. Not until very near the time of the comet's perihelion passage (March 10) will it begin to come within range of most of us in mid northern latitudes.

Unfortunately, reliable information concerning the comet's upcoming apparition has been rather sparse of late. Even the February issue of S&T devotes only a relatively brief and general column to PANSTARRS, although it could possibly prove to be a major spectacle in March.

A major point of conjecture concerning the comet's likely performance centers on the fact that the orbit is ever so slightly hyperbolic, implying that this is the first time PANSTARRS has ever passed close to the Sun. Oort Cloud comets like 2011 L4 carry within them a high potential for not living up to expectations with regard to their brightness predictions. Comets Cunningham, Kohoutek, and Austin have been past prime examples of this. Widely heralded as "Great Comets to be", each dramatically failed to live up to anywhere near their early brightness predictions.

Another rather disheartening fact concerning Comet PANSTARRS is that it will be visible only very low in the west in twilight during almost its entire apparition. So, even if it does turn out being very bright, much of its luster could be lost in the fading glow of daylight.

As if to add insult to injury, the March new moon will enter the evening sky just as Comet PANSTARRS becomes visible, the moon's steadily growing brightness thereafter hampering observations of the comet's tail. However, a rather extraordinary imaging opportunity may exist on March 13th. That evening the thin crescent moon is likely to be seen projected onto the outer portion of the comet's ion tail!

BrooksObs

#4 Jure Atanackov

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Posted 29 December 2012 - 10:23 AM

It's quite amazing to see how the same situation we had with comet C/2006 P1 (McNaught) is repeating with comet C/2011 L4 (PanSTARRS). Observing geometry for comet McNaught during the last three months before perihelion was so poor, that we had almost no useful observations of the comet. It was nearly impossible to make any predictions. The same is now repeating for comet PanSTARRS.

While the comet is still at r~1.7 a.u. and entering the heliocentric distance range where many comets have experienced breaks in their photometric curves, I'm quite optimistic about its current brightness. The last pre-conjunction that I know of and feel comfortable with (experienced observer, good conditions) was by J.J. Gonzalez on August 23 with the comet at m1=9.5 and 6' coma diameter. The last observation of this comet that I know of was by Alexandre Amorim on December 24 at m1=8.1. This was with the Sun at -12° and he only saw 1' of coma, so the comet must actually be much brighter. It's probably pointless to speculate how bright it is, but it just might be doing fine at the moment.

I still vividly remember how C/2002 T7 (LINEAR) fizzled in 2004. It brightened and developed very rapidly in January 2004, heading for a really good show, but then stalled in February and never became brighter than 2nd magnitude. I hope PanSTARRS fares better.
Clear skies!
Jure

#5 Centaur

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Posted 30 December 2012 - 04:43 PM

I've updated my graphics and data based on Solex orbital elements for Comet C/2011 L4 (PANSTARRS): www.CurtRenz.com/comets

#6 Tonk

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Posted 13 January 2013 - 05:05 AM

Oort Cloud comets like 2011 L4 carry within them a high potential for not living up to expectations with regard to their brightness predictions.


Jakub Cerny has posted an analysis of the recent brightness measurements and brightening trends on Comets-ML. He suggests that typical of this class of comet (Oort cloud originator) the brightning trend is dropping and that we should now expect a peak brightness 1 mag lower than the prior prodictions. I've attached a link to his analysis graph


http://www.kommet.cz...s-lc-2013_1.jpg

Analysis is based on 155 visual observations.


Any coments from the experts here? Is this analysis reasonable?

#7 BrooksObs

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Posted 13 January 2013 - 08:57 AM

Indeed, Tonk, Jakub's analysis and conclusions are quite valid and not at all unexpected as far as I am concerned. Comet PANSTARRS only just recently reached the approximately 1.5 a.u. solar distance threshold where dynamically "new" comets often exhibit a distinct decrease in their rate of brightening with approach to perihelion.

One of the biggest mistakes in cometary astronomy (particularly among amateurs) in these days of comets being discovered at enormous heliocentric distances is taking the early photometric data and extrapolating the initial brightness parameters all the way to the time of perihelion, particular when small. Behavior at very large solar distances does not imply the same level of activity will prevail when near to the Sun as the outgassing of different volatiles are involved.

The most famous example of this mistake was, of course, made in regard to Comet Kohoutek some forty years ago. As this widely heralded "comet of the century" crossed the orbit of Mars its photometric parameters steadily slowed until they were reduced to those similar to a simple reflecting body. The resulting celestial display, following months of ballyhooing by the press, turned off the general public to astronomers' credibility for years thereafter.

So, the warning goes out once more to be cautious about what is said concerning Comet PANSTARRS' future. Only its brightness behavior from now on until perhaps the very beginnings of March will actually be predictive of how bright it will look to northern hemisphere observers come mid March - all the beautiful plots and graphs compiled throughout 2012 from brightness data likely having little influence concerning what is yet to come.

BrooksObs

#8 Tonk

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Posted 13 January 2013 - 09:55 AM

Thanks John - nice explanation

... to Comet Kohoutek some forty years ago


I missed the hype (UK press didn't seem to get wind of it) but as a 15 year old on my first ever attempt at observing with binnoculars (prompted by a sky chart published in the Times). I found the comet and got hooked. I have only good memories of Kohoutek for that reason.

#9 Tonk

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Posted 19 January 2013 - 07:34 AM

A revised brightness formula prepared by Seiichi Yoshida from recent magnitude measurements of the comet now puts peak brightness at +3

http://www.aerith.ne...1L4/2011L4.html

Seiichi puts n now at 2.4 with m1 set at 5.5 meaning the comet is less intrinsically bright than originally thought and brightening slower than hoped.

This is a drop from the prior estimate using n = 4.0 and m1 = 4.0.

CN Experts - is this typical with Oort comets? (still learning my way round)

#10 Centaur

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Posted 19 January 2013 - 03:20 PM

A revised brightness formula prepared by Seiichi Yoshida from recent magnitude measurements of the comet now puts peak brightness at +3

http://www.aerith.ne...1L4/2011L4.html

Seiichi puts n now at 2.4 with m1 set at 5.5 meaning the comet is less intrinsically bright than orginally thought and brightening slower than hoped.

This is a drop from the prior estimate using n = 4.0 and m1 = 4.0.

CN Experts - is this typical with Oort comets? (still learning my way round)


Thanks for the info, Tonk. Indeed, estimates for the peak brilliance of a recently discovered distant comet are often reduced (greater magnitude) as it moves closer.

For prediction algorithms, JPL puts the comet total magnitude (M1) at 4.7 and the comet total magnitude slope (K1) at 10. Those are their figures today and have been for some time.

Plugging those figures into the formula puts the current estimated magnitude at +7.1. The greatest brilliance would occur on March 9 at magnitude -0.3.

If your researcher is correct, I suspect JPL will revise its data. At that time I’ll update the related graphics on my website: www.CurtRenz.com/comets

#11 Jure Atanackov

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Posted 21 January 2013 - 03:14 AM


Tonk,

the latest analysis of photometric data by Jakub Cerny shows an even worse trend, with the comet reaching only magnitude 3.5 at perihelion.

Clear skies!
Jure

#12 Tonk

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Posted 21 January 2013 - 04:23 AM

Thanks for the update Jure. I haven't read my comets-ml digest this morning

My purchase of a new high quality camera lens was predicated by the prospects of this comet - decision time being mid February. Looks like I'll defer until the autumn for ISON an fall back to my trusty TV85 for this one as I've plenty of experience with imaging mag 4 comets! If ISON doesn't play ball I'll save some money!

#13 curiosidad

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Posted 21 January 2013 - 09:10 AM

Hello,
Such comets are often very unpredictable, and do not know why, they usually get worse!

#14 Tonk

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Posted 21 January 2013 - 09:44 AM

and do not know why


I think the "why" is understood - its down to comet composition and structure. If that could be ascertained when the comet is remote a better prediction would be forthcoming.

However its usually the other way round - how a comet performs amongst other measurements (orbit/spectra etc) gives a clue to what its made of and its structure. I.e. after/during the event and not in advance :foreheadslap:!

#15 BrooksObs

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Posted 22 January 2013 - 10:34 AM

Hello,
Such comets are often very unpredictable, and do not know why, they usually get worse!


There a number of competing explanations available, with many of the most recently proposed being highly complex and involved. One of the earlier, simpler, models suggested that dynamically "new" comets, like PANSTARRS, approaching the Sun for the very first time have a thin outer crust, or coating, of highly volatile and easily evaporated material. As the comet first approaches the Sun, these materials sublimate very rapidly and give the impression that the comet is brighter and more active than it really is. However, once gone, the deception ends with the comet's more normal, less active, surface exposed, revealing the intrinsically much fainter and tamer object that it actually is. Honestly there are several variations to this interpretation alone, but the one offered here is probably the most easily understood by the average amateur astronomer.

BrooksObs

#16 pogrzex

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Posted 26 January 2013 - 04:54 AM

Hi, any news from last days? Is there even any chance for this comet to be visible with tail in 10x50? I mean from northern hemisphere.

#17 Tonk

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Posted 26 January 2013 - 08:20 AM

You will have to wait until March when it is visible in N Hemisphere

Patience!

#18 BrooksObs

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Posted 26 January 2013 - 09:11 AM

Hi, any news from last days? Is there even any chance for this comet to be visible with tail in 10x50? I mean from northern hemisphere.


The most recent observation that I am aware of is this one:

2013 Jan 24.74 UT; m1=7.2; Dia= 5’; DC= 6; 11x70 B [Chris Wyatt, Walcha, NSW,
Australia]
Twilight, tail to WSW, fan shaped WSW to ESE, tail more defined on the NW edge,
5’ in length on the longest side (WSW), ESE edge much shorter. Bright stellar
pseudo nucleus with diffuse and fainter outer coma.

The comet's current magnitude implies a continuation of the reduced rate of brightening exhibited since its recovery several weeks ago. Considering that currently a rudimentary dust tail is evident visually, this suggests that a more prominent example of such a feature will evolve as the comet approaches the Sun.

However, when theoretically near its brightest and best during March the comet will be situated very low in the western sky and backed by rather bright twilight for Northern Hemisphere observers. While this initially did not seem likely to pose a serious problem when the comet's peak magnitude was anticipated to be zero, or brighter, it is increasingly likely that twilight will indeed be a major factor, along with light from the waxing moon, in this likely fainter comet's visibility.

BrooksObs

#19 Special Ed

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Posted 26 January 2013 - 02:22 PM

Hi, any news from last days? Is there even any chance for this comet to be visible with tail in 10x50? I mean from northern hemisphere.


The most recent observation that I am aware of is this one:

2013 Jan 24.74 UT; m1=7.2; Dia= 5’; DC= 6; 11x70 B [Chris Wyatt, Walcha, NSW,
Australia]
Twilight, tail to WSW, fan shaped WSW to ESE, tail more defined on the NW edge,
5’ in length on the longest side (WSW), ESE edge much shorter. Bright stellar
pseudo nucleus with diffuse and fainter outer coma.

The comet's current magnitude implies a continuation of the reduced rate of brightening exhibited since its recovery several weeks ago. Considering that currently a rudimentary dust tail is evident visually, this suggests that a more prominent example of such a feature will evolve as the comet approaches the Sun.

However, when theoretically near its brightest and best during March the comet will be situated very low in the western sky and backed by rather bright twilight for Northern Hemisphere observers. While this initially did not seem likely to pose a serious problem when the comet's peak magnitude was anticipated to be zero, or brighter, it is increasingly likely that twilight will indeed be a major factor, along with light from the waxing moon, in this likely fainter comet's visibility.

BrooksObs


Today's Spaceweather (26 Jan.) has a recent pic--scroll down the page to see it.

Chris Wyatt's detailed observation report suggests that observers down south are getting a very good look at PANSTARRS. Even without reaching negative magnitudes it could prove to be a very satisfying sight in binoculars or small telescopes come March.

Being low in evening twilight might make for difficult or impossible naked eye observations, but I'll bet it will look good in binoculars.

I know that Comet C/2006 P1 (McNaught) was brighter before perihelion than PANSTARRS will probably ever be, but I needed 10x50 binoculars to get a good view of it just above the horizon when I made this sketch just 2 days before perihelion. Through the binoculars it looked like a magnesium flare. Of course, it then went on to greatness. :cool:

#20 Dave M

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Posted 27 January 2013 - 11:33 AM

I know that Comet C/2006 P1 (McNaught) was brighter before perihelion than PANSTARRS will probably ever be, but I needed 10x50 binoculars to get a good view of it just above the horizon when I made this sketch just 2 days before perihelion. Through the binoculars it looked like a magnesium flare. Of course, it then went on to greatness. :cool:


Be nice if PANSTARRS turned into a Northern Hemisphere (2006 McNaught) :grin:

#21 Dave Mitsky

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Posted 27 January 2013 - 02:53 PM

It certainly would.

Dave Mitsky

#22 BrooksObs

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Posted 27 January 2013 - 03:48 PM

For what it may be worth, I have just performed a linear regression analysis of 24 Southern Hemisphere visual magnitude estimates spanning 2013 January 01 to 26. The results indicate the following brightness formula prevails:

m1 = 5.98 + 5 log(D) + 7.59 log® , n = 3.04

I would note that this is in reasonably good agreement with parameters independently determined by Yoshida recently and indicating a much reduced peak brightness in March than had initially be projected.

However, I would add that the scatter in the data is definitely more that I would like to see.

BrooksObs

#23 Jure Atanackov

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Posted 27 January 2013 - 07:34 PM

I did a similar exercise a couple of days ago with 31 estimates from January 01 to 25 and got: H0=5.7, n=2.8. Both sets of photometric parameters give peak brightness at m1=2.3 (but that's still six weeks away).
Clear skies!
Jure

#24 pogrzex

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Posted 01 February 2013 - 12:06 PM

It's now Feb. the Moon is slowly going away I'm waiting for another obs.

#25 MikeBOKC

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Posted 01 February 2013 - 12:18 PM

There are some good locator charts for PANSTARRS in the new March issue of S&T.






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