Talk:17P/Holmes

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[edit] third minor outburst on march 2008

i just saw 17p holmes on its (supposedly) third outburst about an hour ago... pretty bright enough, however, i've searched the net and there hardly seems to be any much buzz about this 3rd outburst....is this notable enough for entry into the article??? in my opinion yes... but for others... Meynardtengco (talk) 12:40, 13 March 2008 (UTC)

Another outburst? Wow, I haven't seen it since December, when it was only about 40 arcmins accross, now it's probably around 7 deg wide! Eek! Space.com actually predicted a possible second outburst sometime in January. It's probably too faint for me to see anymore, probably only about mag +15 per sq arcmin at the brightest. Ah well. As for the citation, I think we should wait for more people to discuss, although new comments are usually posted at the bottom. Thanks. ~AH1(TCU) 16:59, 13 March 2008 (UTC)

[edit] image

Image:17P-Holmes.jpg does not seem to be good for wikipedia. need to find a better one. or ask for permission to use one that is found on news sites now. 12.106.237.2 20:10, 25 October 2007 (UTC)

I added a quick image to show the position in Perseus. I'm happy if anyone can replace with a better one. Tom Ruen 21:17, 25 October 2007 (UTC)

Where can this comet be seen from (North America?) and in what part of the sky and during what hours? (I'm surprised that informatino wasn't here---not even hinted at.) 128.101.254.41 22:36, 28 October 2007 (UTC)

It is visible all night in the nothern hemisphere. --LiamE 00:09, 29 October 2007 (UTC)
What part of the sky is it in (east, north, south, west?) and how long will it remain in view? -- Mwalcoff 05:46, 29 October 2007 (UTC)
I have added a bit about this to the article, it is referenced to a skymap which should make locating it pretty easy. Hope that helps.IvoShandor 09:12, 29 October 2007 (UTC)
Nice, but the image still requires you to know where Perseus is. In what part of the sky is Perseus? (The Perseus article doesn't help.) -- Mwalcoff 23:02, 29 October 2007 (UTC)
I would guess from the northern hemisphere it would be located somewhere in the north of the sky at some distance from the north celestial pole. Right now Perseus is probably at its highest in the night sky (probably close to overhead) at around midnight. I don't live in the northern hemisphere so I don't know for sure. The comet is essentially unobservable from the temperate zone of the southern hemisphere. -- B.D.Mills  (T, C) 04:41, 30 October 2007 (UTC)
I guess the information is not here because it depends very much on where you live and when you're looking. From northern temperate zones it should be about 30 degrees above the eastern horizon at sunset. If you can find the big 'W' shape of Cassiopia, then look "down" towards the horizon, you will find Perseus --Captain Sumo 09:49, 31 October 2007 (UTC)
Probably. The information varies from place to place, probably doesn't make sense to include it. The fact of the matter is, star charts are easily found, there is a good one in the Sky and Telescope articles used as refs, spaceweather.com has some good ones. Heavens Above has really cool star charts that can be adjusted for location, time etc. IvoShandor 10:23, 31 October 2007 (UTC)

[edit] ITN

This article is now on the front page in the In the News section. I have added a bit noted above. Spaceweather.com says that the comet is exploding and now has a physical size (including gas and particles and dust and such) larger than Jupiter. Can anyone confirm this with a better reference, I am not sure the spaceweather one has a permanent link, or at least I couldn't find one. Also it would be great if someone could drop a couple good refs into the discovery section. IvoShandor 07:38, 29 October 2007 (UTC)

I noticed this in ITN - does anyone know why it grew in brightness suddenly? Have any scientists theorized on it? Neil ☎ 10:15, 29 October 2007 (UTC)
I have seen little on this. At least one site is suggesting the comet exploded. Early reports I saw indicated that this was a normal "outgassing" or similar event. I am not sure anyone knows exactly why though. I will keep digging. IvoShandor 10:34, 29 October 2007 (UTC)

[edit] External link farm

The external links are becoming reminiscent of an agricultural operation which grows external links, several of these should have their relevant material integrated into the article and used as references. Others should just be dropped altogether. Once I look through them all I will see where I can add and try to trim the section to the most pertinent external links. The image gallery should be moved, those are all free use photos so if no one moves them to Commons I will just do it, and request their deletion here, hopefully someone has some time to move them before that though. We should create a gallery at Commons:17P/Holmes.IvoShandor 13:29, 29 October 2007 (UTC)

I have revised the links section, still looking at some of the sites. I dropped all image links, as we have several quality images here that are purely free use. I also got rid of the link to the orbital animation as the NASA one is linked in the refs. I am taking the sites I am incorporating into the refs off of the list as well. IvoShandor 13:43, 29 October 2007 (UTC)
All cleaned up, two links to articles actually had less information than was in our article, so I removed them. I moved the others were moved to the refs section and some info from them added to the article. The three remaining links looked good to me. IvoShandor 15:25, 29 October 2007 (UTC)
No wonder I am on break. This article confirms everything I thought. Someone readds all that external link spam bullshit, and doesn't even mention it here. Nice. I am removing. There are more than enough pictures here, so the APOD stuff is useless. IvoShandor 18:35, 1 November 2007 (UTC)
I don't know what you have against the APOD image links. They are professionally done, informational, and well-cross linked to other interesting sites too. Tom Ruen 18:44, 1 November 2007 (UTC)
It's useless content, doesn't provide anything more than what this article does with its dozens of images, gimme a break. Why link to photos? This isn't google. IvoShandor 18:47, 1 November 2007 (UTC)
If we didn't have all these free pictures it might make sense, but I can't see why we need to link to images, mind you, not one, but three. That is totally overdoing in it, imo. IvoShandor 18:48, 1 November 2007 (UTC)
To clarify, I have nothing against the APOD site, per se. What I am averse to, is the sneaky way they were put back in, I started this thread when I removed them in case someone had issue with that, no one said anything and the links were all reinserted, including one by an editor who appears to operate the a site that was added to the links. Whatever, do what you want. I don't care. Page, err... I mean photo gallery... unwatched.IvoShandor 18:51, 1 November 2007 (UTC)
Nothing sneaky - I didn't see this talk section, just the cleared links after a ton of edits I didn't want to sort through. At some point the internal images ought to be pruned - main annoyance is I'd like to show how the cloud expands, while random photos from users, without proper documentation of the view scale, as well as different equipment makes them difficult to compare. Anyway I re-added APOD as:
Tom Ruen 00:04, 2 November 2007 (UTC)
Someone is definitely going to have to clean up this photo gallery shortly. We now have a weeks worth of photos on one page and this comet isn't going to be disappearing overnight. I certainly support anyone who takes the time to clean it up. SpikeZOM 03:54, 3 November 2007 (UTC)
I put forward the removal of the Cleanup Gallery template, fot this section (it could be moved to some of the above sections though). Although those images could be on Wikimedia Commons, this section is a good visual, encyclopaedic part of the article, covering the evolution of the comet and why it iso notable. It's not a "gallery", but a day, by day visual definition of this unusual comet. Maybe you're mistaking this section for the actual "galleries", above this section ? Thankyou. DJ Barney (talk) 18:17, 21 November 2007 (UTC)

[edit] And?

There is no indication within the article as to whether this is an unusual event. Is it?

WikiReaderer 15:37, 29 October 2007 (UTC)

I added a bit on how a similar outburst was connected to its discovery, so it would appear its not uncommon. I am still looking for sources though, and I hope a few others are too. IvoShandor 16:11, 29 October 2007 (UTC)

[edit] Ideas?

Are there hypotheses/theories out there about why this kind of magnitude shift occurs? Applejuicefool 15:50, 29 October 2007 (UTC)

If you read anything that has an idea, please post it here. I have seen a couple ideas along the lines that this isn't an uncommon type of event, though highly interesting. As to exact cause, I myself am unsure, but am far from a comet expert. I only dabble in amateur astronomy. IvoShandor 16:12, 29 October 2007 (UTC)
Yeah, I'm no expert myself. Any ideas I might have would just be pure conjecture, and this isn't really the forum for that. Applejuicefool 17:09, 29 October 2007 (UTC)
Obviously, but if you do happen to run across something, or read a good piece, make sure you drop a note here. :) IvoShandor 17:23, 29 October 2007 (UTC)
It happens often that comets break apart or start outgassing massively for "no" reason at all.

CielProfond 16:45, 30 October 2007 (UTC)

[edit] who is this person named "kidd" ???...and a suggestion

"It was confirmed by Edward Walter Maunder (Royal Observatory, Greenwich, England), William Henry Maw (England), and Kidd (Bramley, England)."

When u click the link about "kidd" it just goes to a link with basically no information about what or who "kidd" is.Why mention him/her/it and link it to another page if there's no other information about him/her/it ???

Also i believe there should be a section about possible causes for it flaring up like it has as i have no idea why it's done it.82.21.204.72 18:05, 29 October 2007 (UTC)

[edit] The apparent size of a comet in the night sky

I have removed the following line from the article: "On October 26 astronomer John Bortle said that the comet could reach the apparent size of the Moon in the night sky by the time the outburst ends in either a matter of days or weeks.[8]"

A comet with an orbit that is further away from Earth than the orbit of Mars would have to be many times larger than a planet in order to appear as large as our Moon in the night sky. E James (talk) 19:48, 29 October 2007 (UTC)

I don't know, apparently the thing is already larger than Jupiter, from what I have read. IvoShandor 19:51, 29 October 2007 (UTC)
Spaceweather.com is reporting this here. I suppose they could be making it up, but that doesn't seem likely. Thus, Bortle's prediction doesn't seem that far-fetched, I think we should just leave it out for now and see how the event progresses. Thoughts? IvoShandor 19:55, 29 October 2007 (UTC)
Works for me! E James (talk) 20:20, 29 October 2007 (UTC)
The CLOUD of gas and dust around the comet is expanding rapidly and certainly will expand larger than the moon's apparent size, just a question of how bright it'll be then. See how large it is already:[3] at [4]. Tom Ruen 20:29, 29 October 2007 (UTC)
I had no idea that the cloud was already larger than Jupiter. I'm still skeptical about it reaching the apparent size of the moon, though. I did some quick calculations, and that cloud would have to be more than ten times the diameter of Jupiter when 17P/Holmes was at its closest approach to Earth to appear as large as the moon. Of course, since Mr. Bortle is an expert on comets, I will probably end up eating my words. E James (talk) 07:07, 30 October 2007 (UTC)
A little skepticism is healthy to be sure, experts are known to often be completely wrong. I went out to see it tonight, pretty easily visible to the naked eye, interesting stuff. Wow, ten times, that does seem like a lot. I think that Tom's comment above is important to factor in too, its magnitude is likely to decrease in the coming weeks. IvoShandor 07:43, 30 October 2007 (UTC)
It is not larger than Jupiter - its APPARENT SIZE from Earth is larger than Jupiter's APPARENT SIZE.Tk101 —Preceding unsigned comment added by 151.201.104.65 (talk) 18:59, 30 October 2007 (UTC)
It maybe BOTH larger to Jupiter's apparent diameter and actual diameter. I've not seen the numbers, but I (quickly) estimated a 130,000km diameter 3 days ago, so it could easily be larger than Jupiter's 142,000km diameter. [5] Tom Ruen 19:22, 30 October 2007 (UTC)
Very easily, I love anons who write in all caps, and then go back to calling people names in online forums. ;) IvoShandor 10:19, 31 October 2007 (UTC)
Comparing apples to apples, as of Monday, October 29, the diameter of the main coma was 22% of the size of the full moon. I've measured this using the same CCD camera with the same scope at the same magnification. The fainter outer coma was 36% of the the diameter of the full moon. On Friday, October 26, the inner coma diameter was 13% and the outer coma was 23%. This means using the outer coma and assuming the same rate of expansion (remember there's really no friction in this case) the outer coma would be as large as the full moon around the 13th of November and the inner coma would be the same size as the moon on the 24th of November. I doubt if that rate will hold perfectly, plus, as it spreads out, the overall brightness will dim because you'll be looking at it spread over a much much larger area. This means the edges of the outgassing will be harder and harder to spot.FlintstoneStargazer 22:41, 30 October 2007 (UTC)
It appears that I was too quick to remove that line from the article. Thank you to everyone for taking the time to educate me. I notice that the "Outburst" section now includes much more detailed information about the size of the coma, so I will refrain from restoring the original content as-is. If anyone can find a suitable place to insert it, please do so.E James (talk) 20:17, 1 November 2007 (UTC)
Hi. You know, it's not very uncommon for a comet's coma to be larger than Jupiter. It is unncommon, however, for a comet to be larger than Jupiter but have no tail. I was indeed very surpirsed when my calculations showed that Comet C/2002 V1 's coma was larger than Jupiter, but now I'm getting used to the idea. Many comets, like 96P/Machholz 1 (sorry if I didn't remember correctly) have comas that never become larger than the Earth. However, I was very surprised when I calculated that Comet C/2006 P1 (McNaught)'s coma was larger than the Sun. To add to that, the comet's hydrogen cloud could be as large as entire distances from planets. The comet likely will dimmen, not only because of its spreading, but also because of its departure from the sun. This could very well be one of the most notable comets in recent history, up there with Comet McNaught. Thanks. ~AH1(TCU) 21:59, 1 November 2007 (UTC)
Space.com is reporting that the Comet Holmes' coma is now the largest object in the Solar system, even wider than the sun. Mingusboodle 16:53, 15 November 2007 (UTC)

[6]

[edit] From the left hand of Perseus...

Would it be accurate to say that the comet was "at the left hand of Perseus" when it exploded? (the article on the constellation describes an "alternate" linkage for which this is the case, but it doesn't say what that's an alternate to) Also, the article on the mythological Perseus has two pictures of statues where he holds the head of Medusa in his left hand, but is that true of the constellation? I wonder whether an ancient observer would have concluded that Perseus just threw Medusa's head across the skies... 70.15.116.59 23:07, 29 October 2007 (UTC)

[edit] the refs

Hi. Just to let you know, ref #2 is the same as ref #5. I don't have time to fix it now because the refs have different names and places where they are cited. So, could someone come fix this? Also, there are some BadAstronomy posts that perhaps you could cite, but a lot of them are from last week. Is this comet getting more attention than comet McNaught? Should we list the most likely causes for the outburst? Thanks. ~AH1(TCU) 00:44, 30 October 2007 (UTC)

Blogs usually aren't considered reliable sources. I don't know about Phil's however. IvoShandor 02:48, 30 October 2007 (UTC)

[edit] Two questions

The comet is located in Perseus (constellation)
The comet is located in Perseus (constellation)
  1. When does the comet make its closest approach to Earth? (see starchart, moving VERY slowly.)
  2. (since I have zero astronomical knowledge) Which direction should I be looking in, at what time of night, to see this thing? WikiReaderer 23:28, 30 October 2007 (UTC)
    • My astronomy programs show it to be at a closest distance of 1.62 AUs from the earth on November 5 2007. Tom Ruen 23:43, 30 October 2007 (UTC)
    • If you find the stars Capella and Mirphak and draw an imaginary line between them and look a little bit north, you should be able to see it. It is visible all night in the northern hemisphere, look to the northeast in the evening, and northwest in the morning. --Comtraya 23:28, 31 October 2007 (UTC)
Let me add a question: Why did this comet get so bright in the first place? Should be added to the article. WinterSpw 00:04, 31 October 2007 (UTC)
The explanation of the brightness is release of gas and dust from the comet, same as any comet, but the sudden cause is still only speculation. Tom Ruen 00:21, 31 October 2007 (UTC)
What do you mean the sudden cause is still speculation? What makes this brightening event so special? WinterSpw 23:27, 1 November 2007 (UTC)
Most comets brighten only when they get close to the sun. This comet never gets closer than Mars to the sun, and was closest 7 months ago, so it is unexpected that it would suddenly release so much gas/dust like that. Some special event happened, whether triggered internally or externally (collision), and so its speculation to guess what was the cause here. Tom Ruen 23:54, 1 November 2007 (UTC)

[edit] Dates on image incorrect

With regard to Comet Holmes trajectory TLR1.gif, the date 2/15 looks like it refers to the wrong point (during the approach rather than recession) and the gap between 8/17 and 8/31 is too great (should be 2 points not 4). Can anyone fix? Thanks. Secret Squïrrel, approx 03:35, Hallowe'en 2007 (UTC)

Hand-labeling is a bad idea (along with quick effort) - hopefully fixed now? Tom Ruen 03:40, 31 October 2007 (UTC)

[edit] Similar to M31 in Adromeda?

Regarding the comment, "...the comet looked like a fuzzy disk, somewhat similar to the M31 galaxy in Andromeda." I don't want to nitpick too much, and I didn't change it because I wanted to get feedback, but there are two reasons it's fairly different looking than M31 (the Andromeda Galaxy). First, it's pretty much round whereas M31 is oblong. Second, it's much much brighter than M31. Anyway, I was just kind of thinking that the "somewhat similar..." part might be better left off. I'll gladly defer to others on this. FlintstoneStargazer 04:54, 31 October 2007 (UTC)

Comparative descriptions aren't worth much if you have a photograph! M31 is much fainter too! I'd vote to just get rid of the weak comparison. (But I've not worked much on text at all, just graphics!) Tom Ruen 05:03, 31 October 2007 (UTC) Ok, junked it, unsavable sentence. Tom Ruen 05:31, 31 October 2007 (UTC)
Works for me. I think the photo galleries are better than a description of appearance anyway. FlintstoneStargazer 05:44, 31 October 2007 (UTC)

[edit] Actual time of brightening

Is it possible to put in the article exactly how many years ago the brightening event occured (based on its observed position)? Since it is quite a few light years away and varies in its distance from Earth, how old an event are we watching now? —Preceding unsigned comment added by Thinking-ape (talk • contribs) 07:42, 31 October 2007 (UTC)

If it's between the orbits of Mars and Jupiter, then it can between about 4 and 50 light minutes away at most.

--Captain Sumo 09:59, 31 October 2007 (UTC)

Thanks for clearing up the confusion. --Thinking-ape
Approximately 13.5 light-minutes away, given the distance from the Earth shown on the JPL site. SpikeZOM 15:10, 31 October 2007 (UTC)

[edit] Alcheb, Algnib, Mirfak, Alpha Persei?

I am slightly confused with the German interwiki links among some of these stars: Alpha Persei (aka Mirfak or Algenib) has no German interwiki link; Gamma Persei links to a non-existent Alpecher; Alcheb (seen on the one of the comet maps here) redirects to Alpha Persei which does not refer to Alcheb - is this correct?; Algenib yields a disambig with a choice of Alpha and Gamma Pegasi, this seems right. If I've understood this right it seems the problem is partly on the German wikipedia where their de:Algenib article contains two different stars: Gamma Pegasi first, followed by Alpha Persei. The German Algenib then links to the English Gamma Persei. I guess the German Algenib was meant to be a disambig to be linked to the English Algenib. Maybe this isn't the right place to ask, but can anyone make this clearer here and on the German side, and maybe also annotate the Comet maps to clarify which Mirfak and which Algenib is meant?-Wikianon 20:49, 31 October 2007 (UTC)

[edit] I reincorporated my version of the 3d interactive graphic

I reincorporated my version of the 3d interactive graphic. My version is easier to use.

Larry Koehn —Preceding unsigned comment added by Firstmagnitude (talk • contribs) 23:12, 31 October 2007 (UTC)

Yeah, your single purpose, link inserting account is probably not the best way to approach this. You should approach the talk page with the link inclusion proposal since you appear to own the site in question otherwise it just looks like you're trying to drive traffic to your site, which is not something that is allowed. Other editors without a conflict of interest can decide on the merits of the site. Sorry, I won't be replying anymore here, this article has descended into the unredeemable. IvoShandor 18:59, 1 November 2007 (UTC)
Unlike you, IvoShandor, it seems Mr. Koehn is doing a great job for free. Go to his site and have a look. It's not a commercial site, BTW, so I don't see any 'conflict of interest' on his part. I have an advice for you: get a life. 201.19.93.252 02:17, 16 November 2007 (UTC)
Allow me to quote from the style guidelines for external links: "Due to the rising profile of Wikipedia and the amount of extra traffic it can bring a site, there is a great temptation to use Wikipedia to advertise or promote sites. This includes both commercial and non-commercial sites. You should avoid linking to a website that you own, maintain or represent, even if the guidelines otherwise imply that it should be linked. If the link is to a relevant and informative site that should otherwise be included, please consider mentioning it on the talk page and let neutral and independent Wikipedia editors decide whether to add it. This is in line with the conflict of interest guidelines." The site has multiple ads (googlesyndication and 1and1 that I can detect without activating plugins), and is added by the creator, which in my opinion is a clear conflict of interests. I've removed it again, and if I can recall, I'll go through the list and try to slim the list down more later. Can I suggest no one add more external links without a little talk about it on this talk page first? W (talk) 14:53, 26 November 2007 (UTC)

[edit] Magnitude day by day?

Is there a source that lists the 17P/Holmes's magnitude? -- Toytoy 02:24, 2 November 2007 (UTC)

The second link under Notes (from Sky and Telescope) has updated their estimated magnitude day by day. (it's been around 2.8 and brightening slightly to 2.5 in the past day or so) SpikeZOM 02:50, 2 November 2007 (UTC)
[7] But these are estimates by different people, it doesn't literally go up-and-down-and-up-and-down by the hour. Sagittarian Milky Way 21:31, 5 November 2007 (UTC)
Here here, I would also like to see a graph of apparent magnitude over time, from some calibrated (or at least self-consistent) source. There seems to be a nice set of magnitude graphs here, thanks to Tom Ruen's link, that's been updated to about ten days ago, and implies the brigthest time was right after the big brightening. I would like to see some graph like these in the main article. Bob Stein - VisiBone (talk) 08:28, 28 November 2007 (UTC)

[edit] Brightness increase

I agree with user Awolf002's edit and comment. Is the magnitude information really needed in the opening paragraph? Also, I calculated 100^((17-2.8)/5) = 480,000 (to two significant figures). How accurate are the 17 and 2.8 in the article? - Astrochemist 04:53, 6 November 2007 (UTC)

On this lightcurve, the starting magnitude doesn't seem very well pinned-down, between 16 to 18 or more. See also, [8], mag 14.1 I don't know if this large range is actual variance (comets can be fickle things), measurement error, or what?
The most you can say is "hundreds of thousands", and even that only if you accept the first three data points here as authoritative for the starting point. It's stretching significant figures to say half a million. It's a logarithmic scale, At 0.8 mag. error (for example) it's already down to 0 certain digits. And 1 and 2 are indistinguishable. Sagittarian Milky Way 14:37, 6 November 2007 (UTC)
Why is it that the article says the magnitude brightened only a half a million times? It's funny when every article I've read online (including several days' worth of articles linked to on SpaceWeather.com, which is authored by a NASA official), says the comet's magnitude has brightened a millionfold - or even more. See the lead in here:[9], here, [10] here, [11] here, [12] and here, [13] are just a few of many articles to point to the brightening factor of closer to a million than merely just half a million. Srosenow 98 09:29, 6 November 2007 (UTC)
My bet is that some users (or journalists?) have rounded off the apparent magnitudes, before and after the outburst, to simply 17 and 2, respectively. That gives a brightness increase of 100^((17-2)/5) = 1,000,000. I'm in favor of removing the magnitudes from the opening paragraph. They probably don't mean much to the casual reader. Perhaps a light curve could be added later in the article. -- Astrochemist 12:07, 6 November 2007 (UTC)
I think the opening paragraph should include something like:


In only 1.75 days of October 2007, the comet brightened from magnitude 17 to 2.8 — beyond invisible in nearly all nonprofessional telescopes to naked eye in any city. This unprecedented(I'm not sure, better doublecheck) outburst is hundreds of thousands of times greater in brightness.


or,

In late October 2007, the comet brightened from magnitude 17 to 2.8 — beyond invisible in nearly all amateur telescopes, to naked eye in any city, in only 1.75 days. This unprecedented(I'm not sure, better doublecheck) outburst is hundreds of thousands of times greater in brightness.


This way someone who doesn't know the magnitude system can grasp the significance of Holmes while someone familiar with the magnitude system/comets can sense the amazingness from the nunbers alone. And it only takes a few more characters. Sagittarian Milky Way 12:56, 6 November 2007 (UTC)
Yes to something like that. :) Tom Ruen 18:10, 6 November 2007 (UTC)
Agreed! This is a very good idea. Try it out, since it seems to keep the introductory section easy to read for the casual visitor, which should be the goal, IMO. Awolf002 00:09, 7 November 2007 (UTC)
Not 1 millionth as pretty as [1], but I made a graph of estimated magnitude data from [2]. Tom Ruen 01:13, 7 November 2007 (UTC)
Not 1 millionth as pretty as [1], but I made a graph of estimated magnitude data from [2]. Tom Ruen 01:13, 7 November 2007 (UTC)

I did some editing on the opening paragraph as well. Sadly, there are many moderate (and large!) cities in which Holmes cannot be seen. -- Also, the scatter in the brightness (magnitude) graphs cited on this page is quite large at the lower (dark) end, so I qualified the related passage in the article. Astrochemist 22:50, 8 November 2007 (UTC)

I've seen it from Central Park, the street, a train platform with lights in peripheral vision 10 feet away on both sides.. (obvious, fairly obvious, and difficult, respectively) As it spreads out more it looks dimmer, but you can still see it. Maybe older eyes would have more difficulty? The general reader might not realize a comet can look like a mundane star though. Sagittarian Milky Way 10:44, 9 November 2007 (UTC)
Light pollution does affect your perception of it. For the longest time people kept talking about Holmes being non-stellar without optical aid (October 26 in the article) yet I struggled to try to find the tiniest amount of softness in it, even with real stars nearby to compare to. Fuzziness? What fuzziness?! Suggestion bias! :)
Note that the aerith graphs have important data points in the sparsely-covered pre-outburst period, that aren't in the other magnitude table. Complete, kosher, data isn't supposed to come out until something called an International Comet Quarterly, which they expect you to pay for! Sagittarian Milky Way 13:31, 9 November 2007 (UTC)

[edit] So what caused the sudden change? (and other questions)

  1. I am curious as to why this sudden "largest known outburst". If it is the largest known, then it is quite a surprise. What are the ideas explaining why it happened.
    • Still unknown - comets boil when they get close to the sun, creating geysers of gas and dust, but unusual for a comet in such an orbit, never getting closer to the sun than Mars. I like the collision theory, being within the asteroid belt, but unknown odds or expected appearance if it was the cause. Tom Ruen 23:29, 15 November 2007 (UTC)
    • [14]
  2. If the comet was "lost from 1906 to 1964" is that because it was too small to see? Or we our orbits so out of sync it was impossible to find?
    • A little of both I expect, too dim to see accidentally, and orbital calculations take some work before we had computers, most specifically since perturbations by Jupiter will be significant so its orbit is continually changing. Tom Ruen 23:29, 15 November 2007 (UTC)
  3. Also, if the size of the comet is "70% of the diameter of the Sun" (and possibly bigger than the sun), has the comets mass changed? Or is the mass still the same? Is its size getting bigger?
    • The diameter is the gas cloud that is expanding. The comet is just a mile or so in diameter and losing mass very slowly from events like this. Tom Ruen 23:29, 15 November 2007 (UTC)
    • [15]

Kingturtle 20:38, 15 November 2007 (UTC)

Thank you so much for your answers to my questions. Is it possible for you or someone here to incorporate those answers and clarifications into the article? Thanks again! Kingturtle (talk) 14:19, 17 November 2007 (UTC)

[edit] Now that the comet is larger than the sun...

Hi. Now that it's bigger than the sun, that makes two comets so far this year larger than the sun in coma size. The other one was Comet McNaught. Just look at McNaught's SOHO images, the coma was clearly larger than the sun. Should this info be mentioned in either article? Should we create a list of comets whose comas were known to have been larger than the sun? Thanks. ~AH1(TCU) 03:42, 17 November 2007 (UTC)

[edit] Comet to cover Algol?

Hi. The simulation shows the comet covering Algol. When will this happen approximately? The the comet's surface brightness be recognisable at that time? Thanks. ~AH1(TCU) 22:48, 17 November 2007 (UTC)

The orbit simulation shows it closest to Algol around January 22, 2008, ~12 UT. If the gas cloud keeps expanding at a constant rate and stay spherical, it'll be 1.3 degrees in diameter. It's now about 30' in diameter, so that 2.6x times bigger, and if surface brightness is proportional to square of the diameter, ~1/7 as bright. I imagine it'll be hard to see except in photographs, but should be cool! Tom Ruen (talk) 22:55, 17 November 2007 (UTC)
Hi. What diameter of telescope would be nessecary to identify the edge of the coma at that time from the rest of the sky from a light-polluted urban area? Would the comet be visible at that size to the naked eye? Would the center of the comet, the coma closest to its nucleus, be visible next to Algol through binoculars or telescope? Thanks. ~AH1(TCU) 23:05, 17 November 2007 (UTC)
Oh, and if the comet keeps expanding like this, might we see a meteor shower from it in the future and if so when and how strong? Thanks. ~AH1(TCU) 23:13, 17 November 2007 (UTC)
I expect it isn't the size of a telescope that's important, but needing wide angle view with long exposures (and dark skies). I wouldn't expect a meteor shower, since the orbit always stays outside of Mars. Tom Ruen (talk) 23:55, 17 November 2007 (UTC)

I agree there should not be a meteor shower since Holmes orbits at twice Earths distance from the Sun, and the larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by solar winds. Kheider (talk) 04:55, 18 November 2007 (UTC)

The comet is covering Mirfak right now, if anyone wants to see. Any more spread out than this and it'll be very hard to see (depending on sky conditions and magnification). Sagittarian Milky Way (talk) 04:19, 20 November 2007 (UTC)

[edit] Question

Hi. If I uploaded some 15-second exposures using a 4-6 inch telescope and a digital camera sometime in January, would someone be able to take the images and stack them together, and re-upload it onto Wikipedia? Thanks. ~AH1(TCU) 01:07, 20 November 2007 (UTC)

I can't help with stacking but if you find help, I suggest you not abuse wikipedia for storing unneeded images, better to email, ftp, or upload the set to someplace like http://www.flickr.com/ . Tom Ruen (talk) 00:50, 21 November 2007 (UTC)
Hi. Well, how do I email them my images if I haven't uploaded them? The only way I can think of it to put the images on my computer, ask for assistance at the reference desk, ask if I can send someone my images, email them a confimation letter, wait for them to reply, then send an email attatchment to their email adress. Can you think of another way? Is it possible to upload the images to upload.wikimedia, but not the actual wikipedia site? What is ftp? Thanks. ~AH1(TCU) 21:18, 23 November 2007 (UTC)
If someone offered to help, you could email that person the photos as attachments. Alternately you can upload photos for free (up to 1024 resolution) on www.flickr.com if you create an account there. I just didn't see any value in uploading photos to wikipedia unless they are to be displayed. Tom Ruen (talk) 21:36, 23 November 2007 (UTC)
Hello ~AH1, why not try the free software registax to stack the images yourself? I have never done this with astro images but I downloaded it just now and tried it with some old movie frames to extract/improve some unchanging background and it seems straightforward enough. It is a small download on www.astronomie.be/registax and runs on Windows. I tested it with both separate PNG frames and complete AVIs, but do note that images should be raw and unprocessed before stacking. How many images and what size are they? If you have no ftp and need to upload the images I notice that flickr reduces both size and quality of large images (larger than 800 x 800 pixels or so). -Wikianon (talk) 04:15, 24 November 2007 (UTC)

[edit] Featured picture nomination

See: Wikipedia:Featured picture candidates/Comet 17P/Holmes Tom Ruen (talk) 22:04, 20 November 2007 (UTC)