Where in the solar system is Comet Holmes?

It is not enough for me to see Comet Holmes in the sky, I want to know where it is in the solar system, and where it is going. Since I have the software to show me this, by playing with it I learned lots about this very unusual comet. In the next pane I have some diagrams that show the current arrangements of the planets and an animation that illustrates how the Earth and the comet will move over the next few months. [if you cannot see the rest of this article, please click the title… ]

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Most comets that we see have long elliptical orbits that occasionally bring them from the outer solar system (or beyond) to zoom in close to the Sun, and then to journey back to again to those distant realms of frigid darkness and oblivion.

When these little chunks of frozen gasses and dust are close to the Sun, they are heated so that evaporation and sublimation of volatile gasses drives off the clouds of material that we observe as the comet.

Comet Holmes is different, and that is part of what makes this current episode in the sky so strange.

Click this: Comet Holmes at perihelion. The diagram shows the Solar System with the orbits of the planets Mercury, Venus, Earth and Jupiter. This was last May 4th when Comet Holmes was at its closest point to the Sun on this orbit. You will notice that the whole orbit is between the orbits of Mars and Jupiter. So this comet is never very far off in the Solar System, nor does it zoom in very close to the Sun. It spends all of its time much farther from the Sun than chilly Mars, and is never as far away as Jupiter.

That was May. Look at the current situation: the diagram for November 23. Since we are looking down on the Solar System from the North, most objects orbit the Sun counter clockwise. Because the orbit of Holmes is not round, it has moved farther from the Sun. The Earth is closer to the Sun, so it moves around in its orbit quicker, so we are passing Holmes on the inside track. Right now we are about as close as possible on this orbit. While that certainly contributes to our fine views of the comet, it is still very far off — more than 1-1/2 times farther than the Sun.

The big question is, why did this this comet, already very far from the Sun, suddenly increase in brightness more that a million times in one day?

In the coming weeks and months we will be moving farther away from the comet. There is no telling how it will behave, so observing it should be interesting. The following is a short video to show how the planets will move in their orbits from now until 2008 June when the Sun will be between us and Comet Holmes, and for a while we will not be able to see it.

Star maps for observing are here.


3 Responses to “Where in the solar system is Comet Holmes?”

  1. 1 Dona November 23, 2007 at 9:48 am

    very cool stuff Robert! Thanks!

  2. 2 Andy December 16, 2007 at 7:02 pm

    Hey cool blog. One of my brothers lived on Orcas for a long time and I spent a summer there and visited many times. You live in a great neighborhood!

    The thing about the million fold brightening is that we live in an electric universe. A big part of what you are parroting about dusty icy comets getting toasted by the sun… that is all so last millenium, no offense to you, its just that popular science is pretty weak. Google “electric universe” and dive in the water is fine. Life is magical lots of wonderful stuff but you have to dig! Check out “Thunderbolts of the Gods”.



  3. 3 Robert December 16, 2007 at 9:47 pm

    Hi Andy, thanks for dropping by. You are right, there is lots out for folks Googling for those topics. The Thunderbolts video is online, so there is no requirement to buy the video. It is harder to find comments by the scientific community on the subject. Back in my planetarium days I’d think I’d have to fully research those opinions to be able to report accurately the pros and cons. Here, on this blog, I just wanted readers to be able to go outside and enjoy the real-life drama happening right now in the sky. In case anyone wants another view on Thunderbolts, you might begin here: http://forums.randi.org/showthread.php?t=99727

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