Friday, December 5, 2008

Blast From The Past!

It was a year ago that amateur astronomers were marveling over comet Holmes. Discovered back in the 1800s, it was a minor comet that normally would only be detectable with a camera and a good sized telescope. Then on the 23rd of October, 2007 it brightened by OVER A FACTOR OF A MILLION! This is just unheard of, particularly at it's distance from the sun, between Mars and Jupiter far from the sun. It was catapulted to easy naked eye brightness, even with a bright moon in the sky. It was phenomenal! At first appearing nearly star like, it slowly expanded in the vacuum of space.

I first imaged it from my front yard in Tucson. I set up the 14" Celestron and was taking 10 second (!) exposures to keep from overexposing it. Shown here is a stack of 6 exposures showing the mostly spherical shell of the coma, the lack of a tail, and a fuzzy little pseudo-nucleus (the actual nucleus is only a mile or two diameter and not resolvable).

This next exposure is almost 6 weeks later with the same optics, so is shown at the exact same scale. The exposures are a little longer, so more stars show, in fact, a little galaxy shows through the coma to the upper right of the nucleus. It has expanded dramatically in that time, but was still easily visible to the naked eye, and stayed so for several more months before fading in the spring as it continued to expand into nothingness.

About 3 months later on March 8th (2008) the faded comet passed the gaseous California Nebula, and I was able to image it with a 200mm lens. Now a couple degrees across, it was still visible in binoculars and the fuzzy bit of nucleus was still visible.

I read a report recently that theorizes the collapse of an ice cave, releasing millions of tons of ice and dust into the solar system, explaining the sudden brightness. It has something of a history of this - it was in outburst when Edwin Holmes discovered it in 1892. So it has happened in the past and likely will again!

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