The Horsehead Nebula is one of the most recognizable nebulae in the sky. Located in Orion’s Belt, the nebula is about 1600 light years from Earth. The Horsehead nebula was first photographed by Williamina Paton Fleming at Harvard in 1919. The bright star to the left of the horsehead is Alnitak, the leftmost star in Orion’s Belt. The Flame Nebula is in lower left, and the blue patch between these two nebulae is NGC 2023, a reflection nebula. A nebula is an interstellar cloud of dust and gases such as hydrogen and oxygen. Interstellar dust and gases are pulled together to form the cloud we see. As these clouds condense, new stars can be formed. The red color we see in this photo is due to ionized hydrogen gas. The gases are ionized by the energy of nearby stars.
