M42 The Great Orion Nebula

Other Messier Objects

The Orion Nebula is one of the most interesting objects in the sky. To the naked eye, it looks like a star in the sword of the constellation Orion, but with binoculars or a telescope, you can see that it is actually a large glowing cloud of material. This is believed to be a huge star formation region about 1630 light years away. The bright part of the nebula is the glow of many luminous, newborn stars shining on the surrounding gas cloud that they collapsed from. The most important part of the Orion Nebula is the part we can't see: the opaque Orion Molecular Cloud. This is a huge clump of very cold gas that has a total mass of about 2000 times the mass of the Sun. The gas from this cloud slowly collapses due to gravity to form stars. Whenever a bright, new star is formed, its light evaporates the opaque gaseous "womb" it formed from, allowing us to see it.

The stars that are being born in the Orion Nebula are part of what astronomers call an "open cluster." When all of the stars are done being born, what will remain is a clump of a few hundred to a thousand stars which are all roughly the same age (give or take a few tens of millions of years!). These stellar siblings are dominated by a few very massive, very very bright stars called the Trapezium. The Trapezium is made up of just a few stars, but it outshines all the rest of them combined. Astronomers believe that the majority of the glow from the gas in the nebula comes from light from the stars of the Trapezium. Maybe in a few hundred million years, there will be planets like the Earth forming around some of the new stars in the cluster.

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