Two astronomers recently went looking for a monster black hole. They sifted reams of data from the most powerful telescopes on and above Earth for any sign of an invisible object hundreds of times the mass of the sun in a distant cloud of stars known as NGC 6397.

Instead, they found a nest of baby monsters, as many as five dozen: dark engines of annihilation, packed into a space barely larger than our own solar system, buzzing back and forth and throwing their considerable weight around in the dense core of the star cluster.

Eduardo Vitral and Gary A. Mamon of the Paris Institute of Astrophysics, using data from the Hubble Space Telescope and the European Space Agency’s Gaia spacecraft, reported their results Feb. 11 in the journal Astronomy and Astrophysics.