Astronomers have been astonished to find a supermassive black hole in the center of a tiny low-mass galaxy, suggesting that such black holes can form before their host galaxies.
The dwarf galaxy known as Henize 2-10 is undergoing a violent burst of star formation, and is believed to be similar in many ways to infant galaxies in the early universe.
The finding challenges conventional wisdom that black holes form at the same time as their galaxies, and are only to be found in massive galaxies with voluminous spheroidal components called 'bulges' or a nuclear star cluster. Henize 2-10 has neither.
"We never expected to find a supermassive black hole in Henize 2-10," said lead author Amy Reines of the University of Virginia. "We may be witnessing an early stage of galaxy and black hole evolution that has not been observed before."
The discovery suggests that the formation of supermassive black holes may actually predate the build-up of their host galaxies. Reines says she plans to search for other examples to help refine theories as to how supermassive black holes form.
Though Henize 2-10 has been heavily studied for decades due to its extreme star formation activity, its central supermassive black hole went unidentified until Reines and her colleagues found it by chance during a study of dwarf starburst galaxies.
They discovered it after analyzing light emanating from Henize 2-10 spanning radio to X-ray wavelengths. The observations were taken with the Very Large Array, the Hubble Space Telescope and the Chandra X-Ray Observatory.