Comet Holmes (17P/Holmes)
Brief history: Discovered by British Astronomer Edwin Holmes on November 6, 1892. In October of 2007, it brightened over half a million times (from visual magnitude 17...where it would have been a struggle for me to see it in my larger telescope...to magnitude 3, which made it an easy naked eye object). The process that caused this rapid brightening is not understood.
 |
 |
|
|
The nucleus of Comet Holmes at 1 AM (06Z) 16 November 2007. At the time, Comet Holmes was about 2.5 Astronomical Units from the Sun (an 'Astronomical Unit' being defined as the mean distance between the Earth and the Sun, roughly 93,000,000 miles). DON'T COMETS HAVE TALES? By definition, yes the do. Comet Holmes has one, but due to the orbital geometry its not obvious at first glance. The brightest part of the comet is the condensed nucleus. To the lower right, nearly right below the nucleus is the tail. It doesn't look like a tail because we are looking at it nearly "straight on". The only way you can see though a straw is to hold it straight on and the situation here is similar. If you tilt the straw you'll see how long it is. If you didn't tilt it at all it would appear to be of near zero length. Since Comet Holmes was "pointed" at Earth during this appearance we were looking down its long axis with the tail behind the "head".
|
What a difference a year makes! I though I would see how Comet Holmes was doing nearly a year after it's outburst. Above is an animation taken on September 27th, 2008. I took three images about 25 minutes apart in order to reveal any moving objects. Comet Holmes is just to the right of the arrow in these images. It's faded to the point where it's about at the limit of brightness (or faintness) of what I can image. It's somewhere between 19th and 20th magnitude, a far cry from the glory days. So how faint is it? Look at it this way...the brightest star in the above image (the one towards the top) is nine times fainter than can be seen with the naked eye under a clear, very dark sky. Distance from the Sun to Comet Holmes in these images is about 3.8 AU's, roughly 353,400,000 miles. |
 |
 |
|
| Black and white image taken 31 October 2007 at 1107Z. 12" LX200 at f/10 and SBIG ST-9 camera. Eight second exposure. Processed with a dark frame and flat field. North is up, east is to the left. Field of veiw is a 12-minute square. | Above image is a 'false color' version of the image to the left. It makes it much easier to get an idea of what's happening near the nucleus. | |
 |
Comet Holmes on 28 Oct 2007 at 0547Z. Imaged with a 12" LX200 at f/10 with a Canon D30, 30 second exposure. Through
binoculars it appears as a symmertical disk, but at higher magnifications
one can see it's not. |
|
Comet Holmes on 29 Oct 2007 at 0434Z. Imaged with a 12" LX200 at f/7 with a Canon D30, 30 second exposure. This is a slightly wider-field view than the above image. |
Questions/comments, E-mail me at john dot ruthroff at theastroimager dot com
