May 19, 1999
In the grand ledger of cosmic time, a human life is breathtakingly brief. But brevity is not insignificance.
The Horsehead Nebula
Birthday · May 19, 1999
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APOD published May 19, 1999. Credit: AURA. A publication-date match, not a photo taken on your date. Independent of NASA.
One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1500 years to reach us from the Horsehead Nebula. The above image was taken with the 0.9-meter telescope at Kitt Peak National Observatory.
Image credit: AURA