# How far away is comet 17P/Holmes?

The comet is supposed to be as large as the sun right now, but way less dense, of course. But as I understand it, (I’ll look for myself tonight) it appears to be about the size of a fuzzy star. If that’s the case, how far away is it? That would let me know how big the sun would look if the earth were that distance from it, instead of 93 million miles.

This article, dated today, puts it at 1.6 AU (240 million kilometers)

Since that’s not even twice the distance to the sun, shouldn’t it look mighty big right now? It must be getting very close. With the naked eye, how big does it look at this stage?

There’s a diagram on Wikipedia.

And there’s no such thing as “the size of a fuzzy star.” Stars are not fuzzy; they are, for all intents and purposes, infinitely small points of light. Currently the apparent size of Comet Holmes is more than half that of the Moon.

What I meant was that if a star were fuzzy, that would be the size of the comet. I understand that stars don’t have fuzz. I was speaking of appearance. I guess I should have made that more clear.

It’s fuzzy, so it’s hard to describe. The brightness is similar to the stars near it, but there’s nothing else in the sky that’s close to the same size. It’s pretty easy to see for me, even in a residential neighborhood.

Looking at it in a 20X scope, it’s nearly half the diameter of the field of view. Last night I looked at the moon through the same scope and was surprised that it covers about the same amount of the field of view that the comet does, maybe a little larger than the comet but much brighter. The comet doesn’t appear as big as the moon when viewed with the naked eye since it’s so diffuse, but I guess when magnified the dim part becomes visible.

If you can’t tell, I’m not really up on the whole astronomy thing, I was just really surprised I could even see the comet, and even more surprised (like stunned) at how much difference a 20X magnification made.

By an odd coincidence, the apparent size of Comet Holmes is also more than half that of the sun.

Here, play with this and have fun. Must have Java enabled.

Rex - thanks. That was great fun. Excellent gizmo.

Wow! Yep - with binocculars, I can make out a patch of haze up there that’s about the size of the moon, or sun. So, being that it’s about 1.6 AU away, then that ball is really bigger than the sun. That’s so amazing.

So it looks like this is probably as good of a look as we’re going to get for quite some time.

Please tell me where to look, from central Illinois. And don’t use consetellations as reference points - those mean nothing to me. Use the moon, or compass points, instead, please.

In the early-to-middle evening, you should look east-northeast, a little more than halfway from horizon to zenith (higher up and farther north as the evening progresses). If you see the Pleiades (a fairly bright cluster of several stars close to each other, which should be in the east and also about halfway up the sky) look to their left about 45°. It’s pretty easy to see once you know what you’re looking for, but if you have trouble finding it, go somewhere dark after moonset (about 10pm tonight) and let your eyes adapt for a few minutes.

Just look “an inch or so”* to the left of every semi-bright star about half-way between the horizon and straight up in the NE sky. You’ll eventually see a “star” that’s fuzzy. Comet Holmes is just to the left of a couple of bright stars in Perseus, so it’ll be noticeable right away.

*An inch or maybe a little more if you hold your fingers an inch or a little more apart at arm’s length, that’s about how far Holmes is to the left of the stars. There’s nothing else out past it to the left for quite a ways, so you’ll find it.

Ok, listen up, and maybe you’ll learn something, rather than sticking your head in the sand and going “blah blah blah blah blah” until the band goes by. If you can figure out which way is north, look up in the sky about 3/4 way up. You’ll see a main star. That’s the north star. Look to the right of it a little higher up and you’ll see a pretty clear sideways W. That’s a constellation - Cassiopeia. Do not be afraid. You can handle it. Look down about half way to the horizon and a little more to the right. There will be a fairly bright star and some others. Look just to the left of that star with binoculars and you should see a hazy smudge of light that’s as big (in your view) as the moon would be - comet 17P/Holmes. And it’s in the same place in the sky regardless of where you are, by the way.

Look Here If you can pick out the array of stars to the right of it, you won’t have to know their name.

Tris

This is probably your best way to locate Holmes. Right now it is opportunistically placed in the same direction as Mirfak, the brightest star in Perseus. Last night, the center of the halo was in the 9 o’clock position in relation to Mirfak, with the edge of the comet’s halo overlapping the star…now is a great time to watch it day by day as it moves past Mirfak, making a loop in Perseus (that you see on the second diagram on my link).

Here’s another article discussing what might have happened to Comet Holmes which triggered the sudden increase of magnitude.

Just how far north do you think Illinois is? The North Star is as far above the horizon as the observer is above the equator. So for an observer at, say, 40 degrees latitude, the North Star would be 40 degrees above the horizon.

Look, buddy, don’t get carried away with your SDSAB status. 3/4 of the way up vs around half way up - no biggie, especially at night when you don’t know what you’re looking for. Save your nitpicking for something significant.

I’ve found that it pays to overstate altitude angles when telling people where to look in the sky. People often think things that are greater than 60 degrees or so are “straight up” and things as low as 20 degrees can seem nearly halfway up. It’s just a common illusion for most people until they learn to compensate.

While CC may have been less than tactful–and he probably wasn’t intentionally factoring in this correction–he does have a point that his original number may be useful to a new observer. That being said…in the spirit of fighting ignorance, it pays to be exact.