Comet Holmes Update
Published on Oct 26, 2007 at 10:43 am.
12 Comments.
Filed under astrophotography, comets.
Comet 17P/Holmes continues to be bright. Last night I set up a telescope with a few students of the astronomy club and managed to take the following pictures. They aren’t great, but they give an impression of what the comet looks like.
The images were taken with a Nikon D70 at prime focus on a 200mm f/5 Newtonian. The upper one was 5 seconds at effective ISO 1000. The lower one was 1 second at effective ISO 400, with a bit of contrast enhancement.
This comet is continuing to be a surprise. At this distance from the Sun, this kind of activity is almost unheard of. Whatever is going on, an enormous amount of material has been ejected from the comet. This much material suggests a catastrophic event of some sort. But, while this is really strange behavior, it is not entirely without precedent. Comet Holmes did something like this in 1892 when it was discovered. Edwin Holmes had been looking at something else and he turned his telescope towards M31, the Andromeda Galaxy. He got a small fuzzy thing in the finder scope, but when he looked into the eyepiece, he was seeing a comet instead of the galaxy! At the time, the comet was about 4th or 5th magnitude and visible to the naked eye (though probably would not be today in urban skies with modern light pollution). Over the next week the comet faded three magnitudes, to below the unaided eye visibility threshold. It has not been so bright since then (not until two days ago, that is).
Comet Holmes (technically 17P/Holmes) orbits the Sun once every about 7 years. It was at its perihelion early this past summer, and it was at its brightest then. It peaked at about 14th magnitude. It had been steadily fading for the past four or five months, and was getting close to 17th magnitude. Then, in less than a day, it brightened to about magnitude 2.5. That’s about a 600,000 times increase in brightness. That is pretty much unheard of for a comet. Yes, they can brighten by that much, but not in one day! That is something that I don’t remember ever happening since I got into astronomy. I also don’t remember any comet having this much activity this far from the Sun. Of course, this particular comet apparently did something like this 115 years ago (and at about the same time of year, too, since it was discovered in early November).
So, if you want to go looking for the comet, it is still very close to the position marked on the finder chart that I prepared for my previous posting about the comet.
The comet seemed brighter to me last night than it did Wednesday night. It is easy to find, even in full moonlight and with the light pollution on campus. To the naked eye, it still looks stellar (at least in the city, and I suspect in dark skies, too). But, now you can tell in binoculars that it is not quite stellar. It definitely looks like a fuzzy star. In fact, the term “comet” comes from the Latin “coma,” which means hair. Comets were often thought of as hairy stars. This one really fits the bill. For years, I had heard of comets as hairy stars and compared to giant flaming swords. The description always seemed silly to me, since they always looked just like fuzz balls to me. Then, Comet Hyakutake (C/1996 B2) came by. That comet really did look like a giant blue flame! Now, this comet, Comet 17P/Holmes actually does look like a hairy star (at least in binobulars). I think that it is really cool.
In the telescope, though, Comet Holmes is still unlike anything that I’ve ever seen. It looks like a bright disk, with a sharper edge than any comet that I’ve ever seen (though not as sharp an edge as something like a planet). Just a shade off from being concentric with the disk is a bright condensation that is the head of the comet. It is also less star-like than the night before. You get the sense of that in the images above. The central portion is much brighter than the outer parts of the disk, so getting the outer parts to come out well means over exposing the core, and getting the core well means underexposing the outer disk. Visually, I get almost a hint of near concentric rings in the outer disk, but that may have been my imagination.
So, what does the future hold for Comet Holmes? That is just about any body’s guess. 115 years ago, it faded quite quickly. It might do that again. But, the amount of material ejected that is catching the light will take a while to disperse. It is being pushed back by light pressure, and it is forming a tail. However, don’t expect to see a huge tail extending away from the comet. The tail points away from the Sun, and right now that means pretty much away from Earth, too. A comet’s dust tail curves a bit, so you might be able to see the disk above elongate into an irregular shaped oval, and that will be the effect of the tail. But, the head of the comet is still extremely bright and very distinct. That suggests that perhaps there is still a lot of material being ejected, and if that is true, then the comet is unlikely to fade much for at least a couple of weeks. But, who knows? Comets don’t usually do this sort of thing. The one that we know that has done anything like this before was this particular comet 115 years ago, and it faded rather quickly after being discovered. How long it was in outburst before being discovered, though, is not known. The comet may be too dim to see with the unaided eye within a week, or it may remain visible for a month or more. It is really too early to tell for sure. I am not sure that anyone yet knows just what happened to trigger the outburst.
So, let’s all keep watching the comet. For those of you who haven’t gone out and seen it yet: Go look! This is something very unusual.
-Astroprof
Paulo on October 27, 2007 at 6:12 pm: 1
Yes, it is amazing. Luckily I ve been under the mediterrean skies and yesterdaY i was in rural dark skies, today in city skies.
Actually it looks a bit brighter today, and even in dark skies it has that sharp edge huge disk.
Definitely yellowish.
My theory is that either as is passing over the asteroid realm it has made some collision, or it is definitely some strange behaviour!
I dont think it is a simple eruption, it should not have done this when so far away from the sun and in such a short time and with such huge increase in brightness
We have been luckily in 2007! with early this year with comet McNaught shining like Venus in sunset skies and now this never-seen-before eruption!
Explanations are welcome
Don Spain on October 28, 2007 at 12:10 pm: 2
Observed the comet on the night of 10/27/07. Between clouds it was very bright, I would say at least mag 2. Observed with a 100mm achromat, f/6 at 26X and 60X. I barely suspected that there were 2 nuclei in the coma. Did manaage to get a photo with an old LPI through the refractor. The photo does indicated two nuclei. If you would like I can email you the photo.
Don Spain on October 28, 2007 at 12:11 pm: 3
Observed the comet on the night of 10/27/07. Between clouds it was very bright, I would say at least mag 2. Observed with a 100mm achromat, f/6 at 26X and 60X. I barely suspected that there were 2 nuclei in the coma. Did manage to get a photo with an old LPI through the refractor. The photo does indicated two nuclei. If you would like I can email you the photo.
Chris Mastrangelo on October 28, 2007 at 8:07 pm: 4
Comet Holmes has split into at least two nuclei. I observed it from my backyard with a 4 inch refractor earlier tonight. Other reports are starting to be posted to the Sky & Telescope article.
Jack LaMonica on October 28, 2007 at 11:36 pm: 5
My family observed Comets Holmes (as it seems to have split in two) thru our new Meade 10″ lx200. the coma is concentric but it does appear to have 2 nuclei. It is very bright and easy to see with the unaided eye east of, and in line with, Casiopia around 10 pm. Binoculars show it well as a fuzzy ball.
Astroprof on October 29, 2007 at 1:23 pm: 6
My take on the two “nuclei” for the comet is that one of those nuclei is a background star. Comets do fragment, so it would appear perfectly plausible to presume that the two nuclei indicate that the comet split. That would explain the vast eruption, too. However, I think that it is just a star.
Shirin on October 29, 2007 at 4:15 pm: 7
I have never seen a comet like this. It was excellent.
Eric W. Thiede on October 30, 2007 at 3:58 pm: 8
I examined Holmes at about 1 UT 10-28-07 at 150X with the 15.5-inch Clark refractor at Washburn Observatory, University of Wisconsin-Madison. There was one and only one tiny stellar nucleus at that time.
Astroprof on October 30, 2007 at 5:12 pm: 9
What a lot of people thought was a second nucleus was a background star shining through the coma appearing nearly as bright as the comet’s nucleus. So, there were not two nuclei.
Agnes T. Oclarit on November 10, 2007 at 3:14 am: 10
November 8, 2007, as early at 9pm We were at the roofdeck of the Manila Observatory in the Ateneo de Manila University, Quezon City, Philippines, anticipating a view of the so called “exploding comet”, as a catchy description.
As a member of the Philippine Astronomical Society, we set-up the telescopes and got hold of the binoculars, and with the weather and the skies were cooperating that night, by the sight alone of Cassiopeia , I track the view to locate Perseus.
There with the naked-eye alone, can see a fuzzy cotton-like to me image of the Comet 17P/Holmes.
To my delight and the rest of the members, I view it through a pair of binocular, and Wow! clearer and closer than I can imagine it to be!
It amazes anyone , including the crew of a local television station, who covered the night’s news.
Matt Van Auker on November 11, 2007 at 7:31 pm: 11
Wow, I don’t even know where to start…but I must say I am more than a little concerned neither NASA, nor JPL, has made almost not any response to this.
I mean, not that the government ever need to respond to anything at all, but I just thought if they wanted to walk on the wild side, maybe they could use Hubble, Chandra X-ray, or any kind infrared data etc., to make some kind of effort to analyze this thing.
Yeah, like the rest of us have the resources to do so ourselves.
I mean, look at this thing: http://thunderbolts.info/tpod/2007/arch07/071031cometholmes.htm.
It’s basically doing a dance or making a lasso directly around Perseus (as if someone were trying to get our attention).
Not that I’m into astrology (in fact, I am completely against it in principle), but it seems like someone is trying to get our attention (the Comet’s path is stunningly obvious. You might also make note, interestingly enough, the definition of Perseus is found right in between the words persecution and perseverance in any Dictionary).
I have to be honest: I more than admire, Perseus’ role in Greek Mythology killing the Gorgon Medusa(like Indiana Jones, I hate snakes, too. (by the way, as an aside,I also share the same birthday as Harrison Ford, yes, July 13, which is also shared with Patrick Stewart, yes, Jean-Luc Picard, the friggin’ Captain of the Starship Enterprise)).
Anyway, so much for Dancing with the Stars.
But we still don’t have speed, compositonal data (what caused the explosion), let alone any official magnitude data (which usually comes, from what I understand, from Don Yeomans, so we can come to some kind of definitive conclusions about this thing).
And what about a sodium tail? Does it have one?
Did the explosion cause its own tail?
In other words, does it have three (3)?
Well, basically, we don’t have anything here, and we don’t seem to be getting any closer anything in the process.
And any web search you do, is a completely disorganized, sloppy mess.
Wow, I don’t even know what to say…
In the meantime, if any of you can give me the astronomical heads up (perhaps something is hidden, that I’m just not finding, I would more than appreciate it.
I can be reached at mattvanauker@yahoo.com.
Astroprof on November 12, 2007 at 3:50 pm: 12
Just because there are no pretty pictures being posted to the internet doesn\’t mean that the comet is not being studied by NASA and professional astronomers. They are making plenty of measurements, but these data take a while to be analyzed properly before being made public. Wait a month or so and you\’ll likely be hearing all sorts of detailed information about Comet Holmes.