Astronomers used to think that only larger galaxies have black holes

Jan 7, 2014 09:58 GMT  ·  By
Even dwarf galaxies contain active black holes at their cores, a new study suggests
   Even dwarf galaxies contain active black holes at their cores, a new study suggests

It is a well-known fact that a supermassive black hole called Sagittarius A* lies at the core of the Milky Way. Similarly, other medium or large galaxies, either spiral or elliptical, feature such dark behemoths at their cores. Astronomers did not think that even dwarf galaxies can be powered by such objects.

However, this is precisely what a new study has demonstrated. Researchers at the US National Radio Astronomy Observatory (NRAO), led by expert Amy Reines, have just presented a study revealing the existence of more than 100 dwarf galaxies that display signs of harboring black holes at their cores.

The announcement was made yesterday in Washington DC, at the 223rd meeting of the American Astronomical Society (AAS). This discovery goes against established theory, which holds that only larger galaxies have the mass and evolutionary history required for a black hole to develop.

Reines and her team told attendants that this research could help provide more clues about how these mysterious objects appeared and grew early on in the history of the Universe. Astrophysicists argue that the evolutionary histories of galaxies and their black holes are heavily intertwined.

“We've shown that even small galaxies can have massive black holes and that they may be more common than previously thought. This is really exciting because these little galaxies hold the clues to the origin of the first ‘seeds’ of supermassive black holes in the early Universe,” Reines explained.

The research group, which also featured investigators Jenny Greene, from the Princeton University, and Marla Geha from the Yale University, used data from the famous Sloan Digital Sky Survey (SDSS) to search for peculiar dwarf galaxies. More than 100 candidate galaxies were found.

Each of these objects displayed a pattern of light emission that is indicative to the presence of a black hole in larger galaxies. Additionally, the light signatures also appeared to suggest that feeding was occurring in the areas surrounding these black holes. Feeding occurs when matter flows through the event horizon, fueling the dark behemoths, and allowing them to grow further.

“The galaxies are comparable in size to the Magellanic Clouds, dwarf satellite galaxies of the Milky Way. Previously, such galaxies were thought to be too small to have such massive black holes,” Geha told attendants at the AAS conference.

“Finding these small galaxies with massive black holes is an important step toward understanding how galaxies and black holes developed together. These dwarf galaxies are the smallest known to host massive black holes and can provide clues to how supermassive black holes get started in the first place,” Greene concludes.