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Comet 17P/Holmes, Nov 2007 - Jan 2008

 

This comet was predicted to be about 17th magnitude at this time, requiring a very large telescope to see it. However it has produced an outburst of gas and reflective dust which has expanded roughly spherically around it and made the comet plainly visible to the naked eye as a fuzzy star of about 3rd magnitude. A similar outburst in 1892 caused it to be discovered. The comet is about 200 million km from us and the cloud is currently more than 1 million km across. It is in the constellation of Perseus, near its brightest star, Mirfak. It will move slowly past Mirfak in the next few weeks and it will be interesting to see how the dust cloud develops. Perseus is well up in a NE direction in the northern evening sky, beneath the easily recognisable W of Cassiopeia.

I took this photograph between clouds on 8th November 07. A similar view should be obtainable through binoculars.

Photograph of comet 17P Holmes

Canon EOS5D 100-400mm lens @ 380mm 8s f/5.6 ISO800 2007:11:07 19:23:45 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

 New photo 3rd December 07

Photograph of comet 17P Holmes

Canon EOS5D 100-400mm lens @ 400mm 16x4s f/5.6 ISO3200 2007:12:03 18:52:14 - 18:53:30 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

The comet has now moved westwards but is still near the centre of Perseus, to the right of the bright star Mirfak. It has expanded but moved further from us and faded. It is still visible to the naked eye as a fuzzy patch, if you allow a few minutes for your eyes to adapt to the dark. The comet now seems to have a short tail, as the solar wind pushes its cloud of gas in a direction away from the sun, so it is beginning to look more like the conventional idea of a comet. The solar wind is also responsible for the apparent bow wave. That is not indicating the direction of motion of the comet but the direction from it towards the sun. The tail of a comet always points away from the sun, being pushed by the stream of charged particles which constitutes the solar wind. Whether the darker region just outside the bow wave is real or an artefact from GRIP's processing I really do not know. The slight coloration in bands across the image is certainly not real. It comes from the background correction processing, imperfectly attempting to correct for our suburban street lighting.

 Plotted positions

Plot of positions of Comet Holmes when photographed

This plot shows the locations of the comet when the 2 photographs above were taken. Software for creating such plots is now available here.

 New photo 6th January 08

Photograph of comet 17P Holmes

Canon EOS5D 100-400mm lens @ 100mm 11x30s f/4.5 ISO3200 2008:01:06 17:58:21 - 18:04:39 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

The comet is still in Perseus but moving away from us, expanding and fading. The two brightest stars near the bottom of this photo are: on the left, kappa Persei, and on the right beta Persei, also known as Algol.

 New photo 10th January 08

Photograph of comet 17P Holmes

Canon EOS5D 100-400mm lens @ 400mm 24x20s f/8 ISO3200 2008:01:10 1 20:21:34 - 20:37:58 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

The comet seems to have faded considerably in the last few days. In each individual image of the 34 combined here it is barely visible. The bright star is Algol. Comparing this and the previous photo, you can see how the comet has moved only a small distance against the stars in 4 days

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