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Horsehead Nebula

February 13, 2016

Orion is known for some of the brightest stars in the night sky. Betelgeuse, Rigel, the three stars of Orion’s Belt, and several others are all supergiants — massive stars that were born in the last few million years. And the process of starbirth continues across much of the constellation — some of it in one of the most famous dark regions in the night sky.

The Horsehead Nebula stands close to the star at the left end of Orion’s Belt. The nebula forms the silhouette of a horse’s head against a faintly glowing background — a spray of hydrogen gas energized by radiation from another bright star.

The Horsehead itself is a cloud of much colder, denser gas and dust in front of the glowing background. Because it produces almost no visible light, it forms a dark silhouette.

But within its billowy curtains of gas and dust, the Horsehead is giving birth to new stars on its own. The brightest is at the top of the horse’s head. It’s emerging from a cocoon of gas and dust, and its energy and winds are eroding the material around it.

Many other newly forming stars inside the Horsehead are visible at infrared wavelengths, which penetrate the dust. They, too, are eroding their birthplace. As a result, the Horsehead is falling apart. Over time, it’ll fragment into smaller pockets of darkness, destroying the silhouette of the horsehead. And within about five million years, it’ll completely disintegrate — replaced by the glow of many newborn stars.

Script by Damond Benningfield, Copyright 2015

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