Big Black Holes In Dwarf Galaxies

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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

Transcript

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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