HORSEHEAD NEBULA A dark nebula in the constellation Orion, located just to the south of the star Alnitak, which is farthest east on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. SUPERNOVA A supernova is an astronomical event that occurs during the last stellar evolutionary stages of a massive star's life, whose dramatic and catastrophic destruction is marked by one final titanic explosion. This causes the sudden appearance of a "new" bright star, before slowly fading from sight over several weeks or months. INTERSTELLAR CLOUDS OF DUST Most nebulae are of vast size, even millions of light years in diameter. Contrary to fictional depictions where starships hide in nebulae as thick as cloud banks, in reality a nebula that is barely visible to the human eye from Earth would appear larger, but no brighter, from close by. HELIX NEBULA The Helix Nebula, also known as The Helix, NGC 7293, is a large planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest to the Earth of all the bright planetary nebulae. PLEIADES In astronomy, the Pleiades, or Seven Sisters (Messier 45 or M45), is an open star cluster containing middle-aged, hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky.