COCOON NEBULA (APOD 14 Jan 2008)

BMAONE23 · Post by **BMAONE23** » Mon Jan 14, 2008 6:18 am

http://antwrp.gsfc.nasa.gov/apod/ap080114.html
It is indeed a very colorful nebula. I was wondering though, about the two sets of double yellow lines at the 3:00 position. Are they actually parT of the nebula, or are they just reflection from the telescope armiture???

NoelC · Post by **NoelC** » Mon Jan 14, 2008 11:28 am

I believe they are bona fide nebulae, as I can just barely make them out in Rob Gendler's (less deep) image: http://robgendlerastropics.com/CocoonwideM.html

Yellow reflection nebulae are fairly rare, but this image goes so deep as to illluminate the interstellar dirt! Can't say I care for the secondary (and beyond) filter reflections, though. The CFHT people should consider investing in a better set of filters.

-Noel

Cherie · Post by **Cherie** » Mon Jan 14, 2008 4:38 pm

And what is that off to the right that looks like an upside-down tarantula?

starnut · Post by **starnut** » Tue Jan 15, 2008 1:44 am

1. " formed about 100,000 years ago" ? I assume that was when nuclear fusion started in the core, otherwise that seems too short a time for a massive star like this one to form. Even so, shouldn't it take longer than 100,000 years for the heat to reach the surface and make it shine?

2. Why do the two stars on the botton left corners have yellowish "halos" compared with the others which have blue "halos"?

3. I wish there is a way to know if the bright stars are average stars in the foreground or massive stars farther away.

4. The rich star field makes me wonder if the Hippocaros survey has recorded and cataloged every one of the stars.

Case · Post by **Case** » Tue Jan 15, 2008 2:39 am

starnut wrote:2. Why do the two stars on the botton left corners have yellowish "halos" compared with the others which have blue "halos"?

The yellow ones could be of different spectral type than the blue ones. Not all stars are the same color, which is thought to be related to surface temperature.

starnut wrote:4. The rich star field makes me wonder if the Hippocaros survey has recorded and cataloged every one of the stars.

Hipparcos measured upto visual magnitude 11. I suppose some of the stars in the CFHT-Cocoon Nebula field are fainter than that.