For the first time, NASA Chandra X-ray telescope has been used to discover a pair of black holes in dwarf galaxies that are on a collision course. The Chandra team explains.
Credit: NASA/CXC/A. Hobart
Credit: NASA/CXC/A. Hobart
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00:00Visit Chandra's beautiful universe.
00:04Dwarf Galaxies
00:08Astronomers have discovered the first evidence
00:12for giant black holes in dwarf galaxies on a collision course.
00:16This result from NASA's Chandra X-ray Observatory has important
00:20ramifications for understanding how the first wave of black holes and galaxies
00:24grew in the early universe. Collisions between
00:28pairs of dwarf galaxies have pulled gas toward the giant black holes they each
00:32contain, causing the black holes to grow.
00:36Eventually, the likely collision of the black holes will cause them to merge
00:40into much larger black holes. The pairs of galaxies will also
00:44merge into one. Scientists think
00:48the universe was awash with small galaxies known as dwarf galaxies
00:52several hundred million years after the Big Bang.
00:56These galaxies merged with others in the crowded, smaller volume of the early universe,
01:00setting in motion the building of larger and larger galaxies now seen
01:04around the local universe.
01:08Dwarf galaxies, by definition, contain stars with a total mass less than
01:12about 3 billion times that of the Sun, compared to a total mass
01:16of about 60 billion Suns estimated for the Milky Way.
01:20The earliest dwarf galaxies are impossible to observe
01:24with current technology, because they are extraordinarily faint at their
01:28large distances. Astronomers have been able to observe
01:32two in the process of merging at much closer distances to Earth,
01:36but without signs of black holes in both galaxies.
01:40Astronomers have found many examples of black holes on collision courses
01:44in large galaxies that are relatively close by, but searches
01:48for them in dwarf galaxies are much more challenging, and until now, had
01:52never failed. The new study overcame these challenges by
01:56implementing a systematic survey of deep Chandra X-ray observations
02:00and comparing them with infrared data from NASA's Wide Infrared
02:04Survey Explorer, or WISE telescope, and optical data from
02:08the Canada-France-Hawaii telescope. Using this technique,
02:12a group of researchers identified two pairs of merging dwarf galaxies
02:16in separate galaxy clusters.
02:20The first is Abel 133, which is located about
02:24760 million light-years away. The second is
02:28the galaxy cluster Abel 1758s, which is about
02:323.2 billion light-years from Earth.
02:36Astronomers will use these systems as analogs for ones in the early
02:40universe, so they can drill down into questions about the first galaxies,
02:44their black holes, and star formation the collisions caused
02:48many billions of years ago.
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