Wednesday, February 27, 2008

What Is That Dust And Gas In Space Called?

A Nebula. That’s what it’s called, a Nebula. So many people query this on Google and end up at my website, I thought I’d write a post about it.

Actually, I think NASA said it best on their website:

“A nebula (NEHB yuh luh) is a cloud of dust particles and gases in space. The term nebula comes from the Latin word for cloud. Early astronomers also used the term for distant galaxies outside the earth's galaxy, the Milky Way. Such galaxies, called extragalactic nebulae, looked like hazy patches of light among the stars. But modern telescopes showed that extragalactic nebulae are actually systems of stars similar to the Milky Way.”

There are two types of Nebula.

The first type is a cloud of gas and dust expanding out of a supernova. The nebula is the ejecta that speeds away from the core of the star after it puffs off its outer shell. This cloud of dust and gas eventually becomes fodder for the next type of Nebula.

The second type of Nebula the ones that are out there forming new stars. Gravity causes the particles to coalesse. At some point the mass gets dense enough to ignite into a star. Eventually the stuff that was the Nebula forms suns and planets in a constant albeit very long-term galactic cycle.

That’s the Reader’s Digest version.

In the past, some sky gazers thought that other galaxies were Nebulas that were relatively close by. That is because they looked so diffuse. They appeared similar to the classic Nebula. In fact they were objects that were many billions of light-years away and some were much larger than our entire galaxy. Also, there is a term called Planetary Nebula out there. It is a misleading term as Nebula have to little to do with planets (except that they eventually form into suns and planets but that is besides the point.) Early astronomers thought they looked like the disks of planets.

Also, Nebula are the incubators of life. Why? Well, after many, many billions of years of stars forming and then blowing up, the Nebula that they eject became more infused with carbons, oxygen, and all kinds of heavier and more complex elements. While the ratio of hydrogen and helium (the two most common elements in the universe) to the heavier elements is still very high even after all this time, it is enough to have become the basic building blocks of planets and then of course to life itself. This is why Carl Sagan has been quoted as saying that we are all made of star stuff.

Below are a couple more great images of Nebula taken off of the NASA website.

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