Talk:C/2011 W3 (Lovejoy)

Magnitude notes

• Brightest Comet in Over Forty Years (Comet McNaught (C/2006 P1) brighter than -3 mag)

For C/2011 W3 SOHO:

• "What we can and will do, however, is use different exposure times and filters to capture as much science as we possibly can." (Dec 8th)
• "running an observing campaign on LASCO in which we will be taking images with different exposure times and different colored filters in order to maximize the science return" (Dec 14th)
• "It is starting to saturate SOHO images even with narrow filters and shorter than normal exposure times." (Dec 15th 2050UT)
• "The peak brightness was probably in the region of -3 to -4" (Dec 15th 2250UT)
• Lightcurves: http://severastro.narod.ru/sla/com/lc/current/c2011w3.gif and http://aerith.net/comet/catalog/2011W3/2011W3.html
• The absolute magnitude was 15.5 mag before the perihelion, but 11.0 mag after the perihelion. (Recent images suggest that maybe a disintegrating event has occurred.) kheider: When a comet starts to split/disintegrate, it often takes a couple of days for us to notice it because the nucleus will briefly brighten (more aggressive outgassing) as the event takes place.

Breaking up?

• Coma gets weaker (Dec 20th; 0.2AU from Sun; 12° from Sun) : Healthy / Weak
• The sudden appearance of bright rays are not uncommon when it comes to a comet breaking up

JPL database browser

Given the high eccentricity of this comet which is subject to planetary perturbations, the JPL database browser result (using a pre-perihelion epoch) is not accurate for long-term predictions. Using JPL Horizons and a barycentric epoch of 2020 (and a tolerable data-arc of 27 days), Lovejoy has an aphelion of 142AU and a period of 596 years. A more accurate return year is around ~2607. -- Kheider (talk) 13:30, 27 December 2011 (UTC)

While I understand the concern, right now we just have to use what the sources are telling us. When and if they are updated, we'll change the infobox figures, just as I did last night. I see they have updated slightly again, so I'll rework the figures now. — Huntster (t @ c) 20:31, 27 December 2011 (UTC)

• OR: The current best-fit (based on an observation arc of 29 days) is that Lovejoy was at aphelion 150.5AU from the Sun in 1684. -- Kheider (talk) 14:19, 28 December 2011 (UTC)
• OR2: "Using a 40 day (2012-01-06) observation arc": As of 2011-Dec-16 05:00UT, I think Lovejoy may be ejected from the Solar System and will NOT be back. Lovejoy looks like it was at aphelion 136.9AU from the Sun in 1729. Of course a 40 day observation arc is also somewhat lacking for absolute answers hundreds of years into the future.

• Yes, I would guess this last encounter significantly changed its orbit. Given that it certainly lost a huge amount of mass, that's not surprising. The aphelion numbers went up after perihelion, but now seem to be lowering, so I'd give it a good chance of coming back someday. — Huntster (t @ c) 00:31, 14 January 2012 (UTC)

It's OR research but both a heliocentric and barycentric solution using any epoch after perihelion (Dec 16th) shows the comet with eccentricity=1.000036 and aphelion at 6.68×10⁹¹ AU from the Sun. Obviously the calculated barycentric solution only accounts for the mass (of the Sun+Jupiter) and does not account for the mass of the Milky Way galaxy when calculating aphelion. -- Kheider (talk) 01:11, 14 January 2012 (UTC)

How to reproduce my Horizons output.

• Goto Horizons at http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2011W3
• Select Ephemeris Type:Orbital Elements
• Select Center:@0
• Click "Generate Ephemeris" -- Kheider (talk) 01:19, 14 January 2012 (UTC)

I'll fully admit, Horizon's output is pretty darn opaque to me. The stuff at the top I'm familiar with, but the list below I'm not, nor do I really understand why the top is not considered accurate. There's maths involved, and all that. — Huntster (t @ c) 01:55, 14 January 2012 (UTC)

Horizons is intimidating if you have not used it before, so do not feel bad. Assuming you did not get lost following my directions: If you use the default dates and Table Settings you can text-search (ctrl-F) for "2012-Jan-14" and you will see EC= 1.000022 (ecccentricity>1 = Hyperbolic trajectory). Ctrl-End will take you to the key at the bottom that explains what each symbol means. -- Kheider (talk) 02:09, 14 January 2012 (UTC)

Yeah, I saw the eccentricity reports, but I'm not understanding why the top reports differently from the bottom list. Is it because the Dec 5 epoch is used, so the numbers are old? If so, why aren't the newest numbers used by default? (Obviously, I'm pretty new to this specific area.) — Huntster (t @ c) 02:53, 14 January 2012 (UTC)

When you have a gravitational slingshot around the Sun on Dec 16th, an epoch Dec 5th solution shows the incoming orbit more than it shows the outgoing orbit (Jan 2012 epoch). For comets, NASA generally uses an epoch near perihelion simply to generate a single one-size-fits-all solution. Of course most objects have a lower eccentricity and do not pass so close to the Sun (or a major planet). For asteroids, NASA generally recalculates the orbital elements every few months. For example, asteroid 3 Juno currently uses a 2012-Mar-14 epoch solution and comet 7P/Pons-Winnecke still uses a 2008-May-01 epoch solution with perihelion being on 2008-Sep-26. -- Kheider (talk) 03:06, 14 January 2012 (UTC)

Ah. So is it likely or unlikely that a new epoch will be used at some point, or will it forever remain the 5 Dec 2011 epoch? Or, can accurate figures be pulled for the infobox from the Horizons site (for example, by changing the displayed date to 13 January)? Makes me wonder about writing a paragraph or section about change in orbital characteristics, but I suppose that will have to wait until a paper is published, which Battams hinted at. — Huntster (t @ c) 03:31, 14 January 2012 (UTC)

Given that we are dealing with a comet, I suspect the JPL Small-Body Database Browser will keep the pre-perihlion epoch of 2011-Dec-05. We could try referencing that the eccentricity is currently greater than 1. -- Kheider (talk) 03:54, 14 January 2012 (UTC)

Hmm, I might do that...perhaps use the data from the date of last observation (6 Jan 2012). I'll have to think on it. — Huntster (t @ c) 08:01, 14 January 2012 (UTC)

Kheider, do you know how to format a URL to Horizons so that date, type and center is automatically filled in, so it can more easily be used in a reference? — Huntster (t @ c) 01:20, 15 January 2012 (UTC)

Sadly, there is no way to request the osculating elements table as the default for the the web-based Horizons interface URL. The system was designed primarily for ground-based observers and thus the intentional default. -- Kheider (talk) 01:50, 15 January 2012 (UTC)

2012-Jun-04 Solution

Using the same 40 day observation arc, which is not long enough for an accurate solution hundreds of years from now, Horizons shows an epoch 2020 barycentric solution with an orbital period of ~621 years. This would give it an estimated return year of 2632. Paul W. Chodas's 2012-Jun-04 solution does not create a hyperbolic trajectory. -- Kheider (talk) 11:57, 5 August 2012 (UTC)

So how do we reconcile this discrepancy? Also, IIRC, none of the SBDB solutions indicated a hyperbolic trajectory, while most/all of the Horizons data showed hyperbolic. I find this interesting. Obviously my knowledge on this is extremely limited, but I recall reading that early ephemeris data showing an eccentricity of >1 did not necessarily mean a hyperbolic trajectory, but that the eccentricity usually changes to a parabolic trajectory later in the orbit. — Huntster (t @ c) 13:26, 5 August 2012 (UTC)

IF the epoch used for the solution is when the comet is beyond the region of the planets and it still shows the comet is hyperbolic, then there is a chance it will leave the Solar System. For comets, the JPL Small-Body Database always uses an epoch near perihelion and is not accurate long-term for highly eccentric objects that are easily perturbed while leaving the planetary region. On Monday or Tuesday, I can create a solution similar to what I did with Comet Elenin. -- Kheider (talk) 17:36, 5 August 2012 (UTC)

Kheider, thanks for that, though I'm concerned that this edges close to original research, since the only place that explicitly states "621" is your own annotation. While calculation of course arrives at this figure (actually, my own calc gives 622.007431 years...hmm?), unless someone knows how to do this, and how to interpret the mess of numbers on Horizon, it simply isn't apparent. How could this problem best be resolved? Also of interest, Chodas has submitted at http://arxiv.org/abs/1205.5839, using the 698±2 year figure. We'll see if it actually gets published, or if it sticks in the ArXiv limbo.

Additionally, I'm very pleased with how this article has taken shape, and am thinking about nominating for Good Article status. Whaddya think? — Huntster (t @ c) 23:17, 7 August 2012 (UTC)

Oh, and can an Uncertainty figure be determined from Horizon data, so I can throw that in the infobox? (Sorry for the numerous questions here...) — Huntster (t @ c) 23:34, 7 August 2012 (UTC)

The ~621 result is easily verifiable. Your result is just using more sig-figs (2.271882142E+05/365.25 days) for a orbital period that could be ±50(?) years in either direction given the short uncertain 40 day observation arc. I simply used 2.27E+5/365.25 for readability for the average user. I have changed to 2.2718E+05/365.25 to get a number that rounds to 622 instead of truncating to 621. Either way the result is only an approximation given the short observation arc. -- Kheider (talk) 05:12, 8 August 2012 (UTC)

Horizons (since it is using Chodas solution) also gives a heliocentric value of 698 years (2.549526346687016E+05/365.25) for epoch 2011-Dec-25. Chodas also agrees that the comet nominally came to perihelion in 1329 (2011-682; see table 4, pg 10). Notice how Chodas lists the incoming orbital period as 684 years. -- Kheider (talk) 05:12, 8 August 2012 (UTC)

None of that answers the problem. Again, most people will not be able to understand how this figure is derived...I certainly didn't, until it was explained. A reader must be able to independently verify the data being presented, which is why I used SBDB; Horizons is spectacularly user-unfriendly. I'm uncomfortable with its use here, as it involves a lot of picking and choosing and interpretation to derive a final product. I appreciate that it is the most accurate figure available, thus I can only hope an eventual journal article will present something more easily citable. In any case, thanks for your help here. — Huntster (t @ c) 08:39, 8 August 2012 (UTC)

It would be incorrect original research to claim it should come to perihelion in 2709 (2011+698) as none of the references make that statement. Peer-reviewed papers will mention previous potential perihelion passages in hopes that a researcher might be aware of a comet seen during that time. Professionals are not really interested in listing a Best-fit for a future perihelion passage that might be off by decades. For better or worse (from an ease of use standpoint), Horizons has been used to derive the J2000 orbital parameters in the infobox for every major planet. It has also been used in Mercury (planet) ref #72 to help verify Mercury close approaches to Earth. -- Kheider (talk) 15:41, 8 August 2012 (UTC)

Question(s)

I was doing some google researching in an effort to find more info on the orbit of this, and when it would return to our solar system. Is perhaps the reason I'm not finding much because it's such a new discovery that we don't know yet? if so: Should we put that info somewhere? — Ched :  ?  14:17, 29 December 2011 (UTC)

For predicting the return of a long-period comet, you really want a 90+ day observation arc to reduce the uncertainty region in the known trajectory. It is one thing to predict where it will be in 6 months, it is a whole another to predict where it will be in 600 years after the next aphelion point. A 30 day observation arc is tolerable for a crude guess at the orbital period, a 60 day observation arc is usable, 90 days is decent, and 120+ days is good. Given the currently short observation arc of 29 days, I doubt NASA would put a best-fit number on it until the comet becomes almost too dim to observe with telescopes in 30+ days. Of course by then, the general public will have lost all interest in Lovejoy. -- Kheider (talk) 15:18, 29 December 2011 (UTC)

Thank you very much Kheider. — Ched :  ?  22:07, 29 December 2011 (UTC)

GA review

I'm thinking about nominating this article for Good Article status. Anyone have an objection? (and, anyone know why Battams' Sungrazing Comets website is down?) — Huntster (t @ c) 00:14, 4 January 2012 (UTC)

Power fluctuations and a server hardware failure have caused SungrazerComets to go down. I have no objection to the GA nomination and will try and help the article pass GA QC. -- Kheider (talk) 01:05, 4 January 2012 (UTC)

D'oh, forgot there was a Twitter account. Thanks. — Huntster (t @ c) 01:12, 4 January 2012 (UTC)

Comet Lovejoy back to being 200 meters in diameter pre-perihelion

Some Comets like it Hot (Jan. 12, 2012): http://science.nasa.gov/science-news/science-at-nasa/2012/12jan_cometlovejoy/

(The movie version) ScienceCasts: Some Comets Like It Hot: http://www.youtube.com/watch?v=w75lBn1QIaI -- Kheider (talk) 01:45, 14 January 2012 (UTC)

The article says nothing about being back to 200 m...its still saying they *thought* it was 200 m before perhelion, but then raised the estimate to 500 m. (If it's in the video, I can't watch it where I'm at now.) I think we'll have to wait till a published paper says otherwise. — Huntster (t @ c) 08:03, 14 January 2012 (UTC)

Not really a great Wikipedia source: https://twitter.com/#!/SungrazerComets/status/157881066869370880 -- Kheider (talk) 14:45, 14 January 2012 (UTC)

I know that twitter is frowned upon to a large extent; but, are the people at SungrazerComets a recognized authority on the subject matter? I only ask because I've seen it argued that in at least one case (Demi Moore) it can be acceptable to use twitter info. — Ched :  ?  15:50, 14 January 2012 (UTC)

SungrazerComets is Karl Battams at http://sungrazer.nrl.navy.mil/ (the Naval Research Lab). -- Kheider (talk) 16:14, 14 January 2012 (UTC)

I could never support using Twitter or any kind of social media outlet as a source, be it from an expert or otherwise. And, so far, that twitter post is the only place aside from *really* unofficial sources (forums, etc) that I've seen mention the current 200 meter guess. I think we'll get a well-published source soon enough. — Huntster (t @ c) 21:27, 14 January 2012 (UTC)

thank you both - and I agree "navy.mil good - twitter bad" .. lol — Ched :  ?  21:31, 14 January 2012 (UTC)

• another question (sorry) - in the info box there is: Next perihelion: ~2576? .. would it be better to replace the "?" with a ref or group note (perhaps stating something like "based on 30 day evaluation of current trajectory" type of thing? Just thinking outloud. — Ched :  ?  21:47, 14 January 2012 (UTC)

Unsourced text

Transferring from main article since no source was included. Likely http://arxiv.org/pdf/1205.5839.pdf but I'll have to comb through this and others later when I have some time. — Huntster (t @ c) 16:21, 14 December 2012 (UTC)

The definitive elliptical orbit calculated by Z. Sekanina and P. Chodas in 2012 indicated that Comet Lovejoy was a fragment of an unrecorded sungrazer that reached perihelion around 1329. The fragmentation history suggested by these authors was as follows. The major sungrazing fragment split near the Sun during its fifth century return, when it was most likely observed as the Great Comet of 467. The principal fragment returned as the Great Daylight Comet of 1106, but a secondary fragment acquired a longer period and returned about 1329. This also split at perihelion and its principal fragment will return (probably as a cluster of further fragments) around 2200. The secondary fragment acquired a shorter period that theoretically should bring it back during the early years of the present century. Subsequently, it fragmented far from the Sun and one of these fragments became Comet Lovejoy. Other similar fragments may also exist and might return as bright sungrazers in the near future.

It is also possible that the secondary fragment of the 467 fragmentation event acquired a shorter period orbit than the principal and may have returned as the Great Comet of 852; a comet which some astronomers suspect as having been a sungrazer. Assuming that this comet also split near perihelion, the principal fragment may have returned in the 1230s, when it might have been seen as the Great Comet of 1232 (also suspected of having been a sungrazer). The secondary returned about 1329 and again split, as per the Sekanina/Chodas scenario, except that the primary is now thought to have had the shorter period and returned about 1800. The 1232 comet likewise should have returned in the early 1600s. Although no definite sungrazing comets were seen in these years, Chinese astronomers recorded bright starlike objects near the Sun in daylight in the years 1625 and 1630 (which may have been major fragments of the 1232 comet) and in 1774 and 1792, close to the time of the expected return of the principal fragment of the comet of 1329.

Okay, I finally got around to re-integrating this into the article. Well, the first paragraph at least; I was unable to find any supporting sources for the second, which may have been personal research. Nice, though, that the Sekanina paper was accepted into ApJ, which gives it more weight than simply being in ArXiv. I'd also like to integrate the Gundlach paper (arXiv:1203.1808v2) somehow, but I'll have to find a way later. — Huntster (t @ c) 12:47, 13 January 2013 (UTC)

File:Iss030e015472 Edit.jpg to appear as POTD soon

Hello! This is a note to let the editors of this article know that File:Iss030e015472 Edit.jpg will be appearing as picture of the day on July 30, 2013. You can view and edit the POTD blurb at Template:POTD/2013-07-30. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page. Thanks! — Crisco 1492 (talk) 00:17, 15 July 2013 (UTC)

Picture of the day

Comet Lovejoy is a long-period comet and Kreutz Sungrazer which was discovered in 2011. Named after its discoverer, Terry Lovejoy, the comet was nicknamed "The Great Christmas Comet" owing to it becoming visible near Christmas.Photograph: NASA/Dan Burbank

Comet near C/2011 W3 in STEREO images

It can be seen in the STEREO images that as Lovejoy nears perihelion, a smaller object slightly above it, and moving very slightly more quickly begins to appear. Is this another Kreutz comet? What is its designation? 2605:E000:141B:13A:3D0C:51A1:93A3:E509 (talk) 04:32, 5 October 2015 (UTC)

This is mentioned in the article, actually, but I've never seen a specific mention of its designation. Experts say it is almost certainly a fragment of Comet Lovejoy that broke off several decades before perihelion. Looking at https://www.ast.cam.ac.uk/~jds/knos11.htm, based on timing, instrument of discovery and early credited discoverers, I'm almost certain this fragment is SOHO-2203, but I don't know how to confirm this. Kheider, you have any ideas? — Huntster (t @ c) 05:15, 5 October 2015 (UTC)

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