Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

August 3, 1999 The Vela Supernova Remnant Expands Credit & Copyright: David Malin (AAO), AATB

Explanation: The explosion is over but the consequences continue. About eleven thousand years ago a star in the constellation of Vela exploded, creating a strange point of light briefly visible to humans living near the beginning of recorded history. The outer layers of the star crashed into the interstellar medium, driving a shock wave that is still visible today. Different colors in the complex, right moving shock, pictured on the left, represent different energies of impact of the shock front. The star on the left appears by chance in the foreground, and the long diagonal line is also unrelated. Remaining at the center of the Vela Supernova Remnant is a pulsar, a star as dense as nuclear matter that completely rotates more than ten times in a single second.