Update on Comet McNaught
Published on Jan 12, 2007 at 2:45 pm.
7 Comments.
Filed under comets, skywatching.
Definitely, if you are in the Northern Hemisphere, go out tonight or tomorrow night and look for the comet low in the southwestern sky, right near where the Sun sets a few minutes after sunset. It is worth it. The comet continues to brighten as it sweeps by the Sun. There is some speculation that it might break apart, and if it does, then it will really get bright as a lot of fresh material is exposed to the Sun’s heat. It turns out that the stuff that comets are made of is really pretty poor as a heat conductor, so normally only the outer meter or less is actually heated by the Sune enough to sublimate. So, when one breaks apart, there is suddenly a huge surface area that sees the sunlight. Personally, I don’t think that the comet will break apart, but these things are really pretty unpredictable. As you might recall, I didn’t think that it would get this bright, either!
As Darren Addy mentioned in a comment on my previous post, C/2006 P1 (Comet McNaught) has finally gotten close enough to the Sun, as seen from Earth, to have passed into the SOHO field of view. SOHO, the Solar and Heliospheric Observatory, is a joint venture of NASA and ESA to study the Sun. It’s main job is to study the outermost parts of the Sun, and the image that I’ve posted here is a coronograph image courtesy of SOHO. It has the projecte path of the comet marked on it, and near the top you can see a faint smudge that is the comet. Normally, the coronograph shows the outer whispy features of the Sun’s corona, and occasionally big ballooning explosions of coronal mass ejections hurled outward by massive solar flares.
Now, this image doesn’t really give a proper representation of the orbit, though. It shows how the comet passes by the Sun from our vantage point. Actually, it is passing sort of between us and the Sun as can be seen by the following two orbit simulations from JPL. One image is a top view of the Solar System, and you can see that the comet comes between the Sun and Earth. But, the other image is a sort of side view of the Solar System, and you can see that the comet’s orbit is nearly perpendicular to the orbit of the planets! This is why it is visible mainly for Northern Hemisphere observers at the present time, but is about to swing around and be best viewed from the Southern Hemisphere after closest approach to the Sun.
Now, a couple interesting things about this is that often comets are brightest the closer they are to the Sun, so Comet McNaught might be brightest this weekend. But, fissures and such that open at closest approach, and the material spewed out when so close to the Sun tends to be pushed back to make an impressive tail, so most comets have more spectatular tails after perihelion (closest approach to the Sun) than they do before perihelion. That means that the Southern Hemisphere observers might get an even brighter comet to look at, even without it breaking up.
Another interesting thing here is that comet tails point basically outward from the Sun (the dust tails tend to curve a bit). So, the tail is pointing more or less Earthward right now. That means that if this comet weren’t almost on a line between the Sun and Earth, it would likely have an even more impressive tail (in terms of length). But, the tail pointing nearly at us has the added bonus of making it appear brighter due to forward scattering of the sunlight passing through it, not to mention that it appears less diffuse when looking though it the long way. That mens a much brighter tail that it otherwise would have.
So, if you have any chance at all, go look for it! For my Southern Hemisphere readers, there is a really nice posting on Comet McNaught by Siding Spring Observatory. You’ll find some useful information there to guide you in observing it.
Note:Â I have an update to the Comet McNaught update here.Â
-Astroprof
Images courtesy of NASA, SOHO, JPL
Astroprof’s Page » C/2006 P1 — another Comet McNaught on January 12, 2007 at 2:47 pm: 1
[…] Update: Since I wrote this, Comet McNaught has really flared up and has really become impressive! Despite claims that it rivals Venus, it actually appears much dimmer to the eye. Still, it ought to be visible if you have a good horizon and not too much light pollution or haze. I was in the American Astronomical Society Meeting in Seattle all this past week, but on the way home I got to see the comet and even take some photos. They are here. Also, I’ve posted an update on the comet here.  […]
Jerry Sheehan on January 12, 2007 at 11:10 pm: 2
Very nice update. I stumbled across this site via google. My son and I saw McNaught about 0100 UT 1/11/07 from suburban Seattle. Very naked eye and spectacular through Orion 9X63 binoculars. Clouded out 1/12/07. Will it reappear to the northern hemisphere outbound?
Astroprof on January 13, 2007 at 4:14 am: 3
After it swings by the Sun this weekend, it will be much better positioned to see from the southern hemisphere. Technically, it will be above the horizon as seen from the northern hemisphere, but it will be very low on the horizon during bright twilight, or else up at the same time as the Sun. That means that we won’t likely see it, unless it crumbles and then gets REALLY bright. There have been comets visible in the daytime before, but they are exceedingly rare. I’d be surprised if this were one of them. But then, Comet McNaught has already surprised me!
A Ler…-- Rastos de Luz on January 14, 2007 at 8:21 am: 4
[…] “Update on Comet McNaught“, no Astroprof’s Page. Ainda sobre o mesmo tema, “Watching Comet C/2006 P1 (McNaught)“, no The Planetary Society Blog. Observadores do Hemisfério Sul, Beware… […]
Astroprof’s Page » Comet McNaught’s Tail on January 15, 2007 at 1:24 pm: 5
[…] I mentioned a bit about comet tails both in my Comet McNaught update, and even more in the post immediately prior to this one. Basically, there are two types of tails, the Type I ion, or gas, tail, and the Type II dust tail. The ion tail is typically bluish, and it is carried almost straight outward away from the Sun by the solar wind. But, the dust tail is a bit more complicated. It is pushed outward by light pressure. When the dust shed by outgassing of the nucleus of the comet, it forms a cloud around the nucleus. Most people don’t realize it, but light can actually push on things. So, the light from the Sun is able to push the tiny dust grains outward. But, these dust grains are still orbiting the Sun. So, a push outward causes them to be pushed into farther orbits. The farther an orbit is from the Sun, the slower it moves. So, these dust grains lag ever so slightly behind the nucleus of the comet. The farther they are pushed, the more they lag, so the tail gently sweeps backward, though still largely pointing away from the Sun. The result is a bifurcated tail, one bluish Type I and one yellowish Type II. I’ve included a (not particularly well drawn) diagram to show this. […]
hannah on February 28, 2007 at 1:06 am: 6
i need to know what path does mcnaught’s comet take please tell me
Astroprof on February 28, 2007 at 3:31 pm: 7
Rather than answer in the comments, I made a new post about this. I hope it helps.