Type Ia supernova have been used for many years as a standard candle to measure distances in astronomy. These supernova are thought to occur when a white dwarf star gains mass from a nearby companion. The white dwarf can continue to gain in mass until it reaches about 1.38 solar masses. At that point the white dwarf will go supernova with a consistent peak brightness. Knowing that peak brightness, one can then measure the distance to the star now gone supernova, and can thus measure the distance to the host galaxy. Using this standard candle, astronomers were able to measure the expansion of the universe. In 1998, astronomers discovered that the universe is accelerating.
NASA has just released new images from the Chandra X-ray Observatory of our neighboring galaxy, Andromeda. If Type 1A supernova are caused by accretion, then astronomers would expect to find significant X-ray emission in advance of the supernova. However, if Type 1A supernova are caused by a binary pair of white dwarfs merging, then astronomers would expect to find lower X-ray emission in advance of the supernova. Chandra’s images show that X-Rays are 40 times lower than would be expected if Type 1A supernova are caused by accretion. Therefore it is more likely that Type 1A supernova are caused by merger.
Until now, this binary pair merger of white dwarfs was thought to be rare. Chandra’s images show that this is the more likely case, at least for Andromeda and the six elliptical galaxies that were observed. More studies need to be conducted to see if this holds true for other galaxies.
This composite image of M31 (also known as the Andromeda galaxy) shows X-ray data from NASA’s Chandra X-ray Observatory in gold, optical data from the Digitized Sky Survey in light blue and infrared data from the Spitzer Space Telescope in red.
via : NASA’s Chandra Reveals Origin of Key Cosmic Explosions
via : Andromeda Galaxy
