Incredible Comet Bigger than the Sun

Pretty amazing stuff.

Quote :

By Robert Roy Britt
Senior Science Writer
posted: 15 November 2007
10:38 am ET

A comet that has delighted backyard astronomers in recent weeks after an unexpected eruption has now grown larger than the sun.

The sun remains by far the most massive object in the solar system, with an extended influence of particles that reaches all the planets. But the comparatively tiny Comet Holmes has released so much gas and dust that its extended atmosphere, or coma, is larger than the diameter of the sun. The comparison is clear in a new image.



"It continues to expand and is now the largest single object in the solar system," according to astronomers at the University of Hawaii.

The coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers), based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. They used observations from the Canada-France-Hawaii Telescope. The sun's diameter, stated differently by various sources and usually rounded to the nearest 100, is about 864,900 miles (1.392 million kilometers).

http://www.space.com/spacewatch/071115-comet-holmes-size.html

The contrasting colors of the images produce a nice optical effect if your stare at it for a few moments. The blue comet appears to recede into the black background. The bright sun seems to emerge from the background.

Yeah pretty cool.

But it returns to original size when you blink.

Are we gonna see this comet?

if you have a good pair of binoculars and live in the northern hemisphere you can see it quite well.

It's traveling through Perseus (spelling?) in the north east sky right now. It should be pretty visible this weekend from what I gather.

If it's bigger than the sun then why don't we see this huge blue object in the sky? Is it further away?

This reminds me of something I have trouble comprehending. Maybe you all can help. I can't comprehend how we can see stars with the naked eye since they are at least light years away. If the sun was touching the atmosphere it would appear that all of space is fire and if it started moving away from us it would appear to be shrinking. The sun is 8 light minutes away and it looks alot more tiny than if it was touching the atmosphere. If it was 16 light minutes away it would appear much smaller than now. If it was 32 light minutes away it would look even small than that. So, if it was moving away from us it would appear to be shrinking and eventually it would appear that it disappeared. Since it looks as small as it does only 8 light minutes away it seems to me that it wouldn't be seen way before it got even a light month away. I know I'm wrong about this but I can't figure it out.

Schizophretard wrote:

If it's bigger than the sun then why don't we see this huge blue object in the sky? Is it further away?

Yes it's about 1.6 times the distance from Earth to the Sun away. The other reason why it's not as visible as the Sun is because the Sun is much much brighter than it. Which is also why we are able to see the stars that are so far away. It's because they are incredibly bright.

Schizophretard wrote:

I. I can't comprehend how we can see stars with the naked eye since they are at least light years away.

I suspect that, after a few lightyears of distance, perspective is no longer a significant factor in seeing stars. All that matters is that a few photons eventually reach the Earth by a curving, and sometimes deflected, path. Telescopes can distinguish the size (magnitude) of individual stars, not so much by diameter (or parallax), but by brightness (i.e. how many photons per second).

Your question reminds me of an old thought experiment to prove that the universe is not eternal: If the universe were eternal in duration, and infinite in extent, then the night sky should be as bright as day from the light of an infinite number of stars in all directions. As I remember it, this challenge doesn't hold-up for an expanding, evolving universe.