Friday, October 13, 2006

Cosmic Chesire Cats in M16

Given the tradition of Friday cat-blogging I thought I should start presenting some astronomical cats. The most famous of which is the one lurking in M16, aka the Eagle Nebula, aka the Pillars of Creation.

The cat visible in the image to the left has an angular size of about 15 arcseconds (lengthwise). M16 is about 2.0+/-0.1 kpc distance from us (about 6500 light years), so the physical size of the structure that looks like a cat is (15/3600) * (pi/180) * 2000 = 0.145 pc long, or very roughly about 2.8e12 miles (say three thousand billion miles) long.

I was reminded about the Eagle Nebula by Gagne et al's (2006) preprint on arXiv.org regarding a Chandra observation of M16. Unfortunately the Chandra X-ray image is rather dull looking (to me) as you don't see the nebula (its only a HII region/PDR, so the temperatures in the gas are too low for X-ray emission) but only the young stars.

The cat's ears are actually tipped by EGGs (Evaporating Gaseous Globules), which either are the same thing as Proplyds, or will evolve into them (there seems to be some argument about this). Proplyds are thought to be young solar systems (maybe with planets, but mainly they're comprised of a very young star still in the process of forming), and M16 is covered in EGGs/proplyds (hence the Pillars of Creation moniker).

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