Instructions: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Input: A mass extinction at the end of the Ordovician period is suggested to have been caused by one of these. In 2000, NASA launched the High Energy Transient Explorer 2 to detect them as their signals reach earth so ground observers can better study them. About a million times more numerous than supernovae, they are thought to be the result of a collapse of super-massive stars or collision between compact objects like a black hole and a neutron star. For ten points, name these astronomical phenomena that release a large amount of its namesake radiation.
Output:
Science