One thing that’s known about black holes: They’re big. As in, millions or billions of times the mass of our sun big, in the case of some super-massive black holes. One would imagine, then, that keeping such a monstrosity hidden would be difficult, even in the vastness of space. Apparently not. Not only can they exist comfortably within galaxies but they can even hide within small dwarf galaxies, according to astronomers at Yale.

The scientists have found more than 100 dwarf galaxies presenting indicators that black holes likely lie at their center. The findings are challenging previous studies (and common sense) that suggested something one billion times the size of the sun could only hideout in a comparably large galaxy.

“These galaxies are comparable in size to the Magellanic Clouds, dwarf satellite galaxies of the Milky Way,” said Geha, associate professor of astronomy. “Previously, such galaxies were thought to be too small to have such massive black holes.”

Dwarf galaxies are small, faint, low-mass galaxies with relatively few stars, unlike our home galaxy the Milky Way. Black holes are points in space where matter is packed so densely that light itself cannot escape (usually the result of a collapsing star); massive black holes are an extreme form of black hole.

The scientists said that patterns of light emission from many of the galaxies suggest the presence of massive black holes. The black holes in the study are about 100,000 times the mass of Earth’s Sun — massive, but vastly less dense than black holes seen in larger galaxies. The size of a black hole normally corresponds to the size of the galaxy that contains it, but obviously not always.

“We’ve shown that even small galaxies can have massive black holes and that they may be more common than previously thought,” said Amy Reines, of the National Radio Astronomy Observatory (NRAO). “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,” she said.

“Finding these small galaxies with massive black holes is an important step toward understanding how galaxies and black holes developed together,” said Jenny Greene of Princeton University, who collaborated on the study.