Supernovae are in the news this week, as two papers in the latest release from Nature provide fresh perspectives on stellar explosions old and new. The old one is Supernova 1987A, the closest one in the age of modern astronomy, which has recently undergone a brightening that indicates a key transition in its evolution has taken place. The new one is actually an entirely new category of supernova, represented by four examples. The output of this new category is heavily biased towards the blue end of the spectrum, it's ten times brighter than a Type Ia supernova, and we aren't sure what could possibly be powering it.
Some basic background on supernovae will make it easier to understand both stories. The initial collapse of a star creates a tremendous explosion, one heralded by the arrival of neutrinos and high-energy photons. But the fusion events that accompany the explosion also produce some unstable radioactive isotopes, such as nickel-56 and -57 and titanium-44. Both immediately after the explosion and for the following several years, the remnant of the supernova is primarily lit by energy released as these isotopes decay. Only after a few decades do other processes, primarily the interaction between the expanding shell of the explosion and the stellar environment, begin to dominate the light seen at the site of the supernova.
Posts
No comments:
Post a Comment