Thursday, July 26, 2012

Celestial Lagoons

Today I have a picture of the Lagoon Nebula, a lovely star-forming region in Sagittarius. It is similar in nature to the famous Orion Nebula and is similarly visible, very faintly, to the unaided eye. It is over five times larger than the Orion Nebula (110 light-years across vs. 24), but appears slightly smaller on the sky due to its greater distance (3,000-4,000 light-years away, compared to ~1,300 for Orion).

Messier 8, the Lagoon Nebula in Sagittarius.
Like the Orion Nebula, the reddish color comes from hydrogen ionized by hot, massive young stars embedded in the nebula. The blue color comes from light scattering off dust in the cloud, similar to the way air molecules scattering light causes the sky to look blue.

The Lagoon Nebula is also similar to the Orion Nebula in that they both offer looks into the cavernous interiors of gigantic clouds of cool gas and dust. From the outside these clouds appear dark and boring, and you can see that slightly around the edges of the nebula. But when young stars inside them blow away the gas around them and offer a view inside, the sight is spectacular. Not unlike geodes, now that I think about it. (Geodes, for those who don't know, are rocks that look like any other rock on the outside to the untrained eye, but which contain beautiful crystal formations on the inside if broken apart.)

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