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: The Palomar-Green survey catalogued several of these objects, and the Soltan argument posits the existence of "dead" ones of these if they are powered in a certain way. X-ray binaries are sometimes referred to as "micro-" ones, and another type of these objects are similar to BL Lac objects and can change output by up to 50% in a day, referred to as optically violent variable ones. Neutral hydrogen in the interstellar medium leads to a suppression of emissions from these objects on one side of the Lyman-alpha line, known as the Gunn-Peterson trough. A double one of these dubbed "Old Faithful" was the first gravitationally lensed object observed, and another is known as Einstein's Cross. FTP, name these stellar objects, which are distant galaxies with a supermassive black hole at their center, whose name originally meant "quasi-stellar radio source".
Output:
Science