Via Universe Today I saw this video time lapse of comet Lulin as it blows gas off its nucleus:
This was taken by Joseph Brimacombe, Southern Galactic Telescope Hosting, on February 22, 2009. The solid part of a comet is usually pretty tiny, just a few kilometers across. Bigger than a mountain, but a lot smaller than a moon. But a lot of that solid part is frozen stuff that turns into gas when the comet nears the Sun. It expands, forming a cloud around the solid nucleus. That cloud can be huge– 100,000 kilometers across or more, bigger than planets!
The gas escapes away from the comet, forming a tail. That tail can get kinks, twists, sheets, ribbons, all kinds of shapes as it moves off. In the video, you really get a sense of the majesty and beauty of this process. As the tail fans out, sometimes it looks like we see part of it on both sides of the comet, but that’s just a perspective effect. Imagine someone with long hair in the wind; their hair forms a comet-like shape behind them. Looking straight at them, face-on, you’d see hair on both sides of their head. That’s more or less what we see with Lulin. You can see the so-called anti-tail in lots of the images posted of Lulin. Try a Google image search and be amazed. This is some gorgeous comet.
March 2nd, 2009 at 9:26 am
as it blows gas off its nucleus
/me cringes, waiting for Internet Rule 34 to kick in
March 2nd, 2009 at 9:35 am
I am dissapointed as it is not visible through unaided eye in this part of globe ,i.e.Varanasi,India.
March 2nd, 2009 at 10:04 am
100,000 km?
Are you sure about that?
March 2nd, 2009 at 10:27 am
Current position of Comet Lulin (C/2007 N3)
(Click on image for the JPL/NASA interactive tool).
March 2nd, 2009 at 10:45 am
@QUASAR,
I remember observing comet Holmes in 2007 with binoculars and my little 4.5″ scope. It went from magnitude 17 to about 2.8 in less than 48 hours, making it easily visible to the naked eye.
From Wiki (for what its worth):
So I guess you’re right, 100,000km is not very big for comets, especially ones that can be seen with the naked eye.
March 2nd, 2009 at 11:12 am
@ Greg in Austin
You were viewing it with a ground based telescope and you know how distorting the atmosphere can be! And on that scale, if the comet was just 10 cm across, the the coma would be more than 1 to 10 km in diameter!
How big was Hale Bopp’s coma?
March 2nd, 2009 at 11:41 am
QUASAR said,
What? Atmospheric distortion has no effect on the actual size of the comet. At that time, the comet was located out between the orbits of Mars and Jupiter (1.635 AU, or 244,592,730 km from Earth) yet it was visible as a fuzzy object larger in appearance than Jupiter itself. In order for comet Holmes (with an estimated nucleus size of 3.4km) to be seen from earth over 244 million km away, its coma had to be enormous.
I don’t know. Why don’t you do some research on your own and tell us?
March 2nd, 2009 at 12:21 pm
@ Greg in Austin
Well, I think you do realize what you’re talking about here, don’t you?
A comet with a nucleus less than 10 km in diameter and it has a coma that’s way bigger than the Earth’s diameter!
March 2nd, 2009 at 12:24 pm
And I really don’t think that the coma is really that big! Maybe it’s just the intense brightness that makes it seem so large!
March 2nd, 2009 at 1:09 pm
Are you sure that’s not just a road flare, shot in slow motion?
Seriously, very cool that they could accomplish that.
March 2nd, 2009 at 2:27 pm
@ Greg in Austin:
Perhaps comet Holmes took some pills to increase the size of its coma.
March 2nd, 2009 at 2:34 pm
@ Joe Meils & ncc1701
Those two are hilarious!
March 2nd, 2009 at 3:39 pm
For the benefit of QUASAR, who would rather make unsupported statements than do some 5 minute research;
The maximum extent of the coma observed around Hale-Bopp when it was near the Earth and the Sun in early 1997, was 2-3 million km, or only a few times more than now; the uncertainty arises from the different observational methods used. Comae of other comets rarely ever become larger than a few hundred thousand kilometres. There is little doubt that the exceptional dimensions of the coma around Hale-Bopp is a direct consequence of its unusually large nucleus. Although it never became possible to measure its size accurately, a variety of observational methods points towards a diameter in the 40 – 70 km range. The nuclei of most other comets are at most a few km across. With its larger surface, more material is released — this provides a natural explanation of the unusual coma of Hale-Bopp.
All above information from http://www2.jpl.nasa.gov/comet/eso28.html
March 2nd, 2009 at 3:48 pm
Yeah, how ’bout that Holmes? Bigger than the Sun?!
March 2nd, 2009 at 4:32 pm
QUASAR said,
The great thing about science, is you don’t have to believe anyone else. You can test it for yourself.
If you have binoculars or a small backyard telescope, with a known magnification and field of view, you can observe the comet’s apparent size. Then, if you look up the position of the comet in its orbit (from data collected by people who have been observing it for months or years), you could determine its distance from Earth, and then calculate its actual size.
Again, since you don’t want to believe anyone here, you could spend 5 minutes googling “astonomy comets” and find hundreds of articles that support Phil’s claim. One good little source of information: astronomy.com/asy/default.aspx?c=a&id=2295. Or, you can do a little bit of research and experimentation yourself. Go out tonight and look at the sky, and then come back with your findings.
March 2nd, 2009 at 4:39 pm
QUASAR said,
What’s the big deal? The Earth is not at all very big, compared to Jupiter, Saturn, or the Sun. And space is huge. Why is it so hard to fathom a giant chunk of rock and ice heating up and spewing out gas for thousands or millions of kilometers?
If the size of these comets is unbelievable to you, then don’t go looking at stellar nebula or supernovae!
March 3rd, 2009 at 6:03 pm
So, QUASAR, how’s that research going?
March 4th, 2009 at 7:22 pm
@Greg,
S/he’s way too busy looking for other threads to troll to do research.