COIMBRA, Portugal, Aug. 11, 2026 - The young stars orbiting Sagittarius A, the supermassive black hole at the centre of the Milky Way, probably formed where they are now rather than migrating there, according to a study published in Astronomy & Astrophysics. That is a puzzle, because conventional star formation cannot happen so close to the black hole.

The team, led by Rodrigo P. Silva, counted how many stars in the S cluster, the group closest to the black hole, come in pairs. They measured a binary fraction of 43%, give or take 9 percentage points. Their simulations predicted 38%, give or take 10 points.

The black hole's tidal forces reduce the share of stars that stay in pairs nearby. The close match between the measured and the modelled numbers supports the idea that the stars were born in place.

Space Nugget. Stars are born when a cloud of gas and dust collapses under its own gravity. Near a supermassive black hole, the pull on the near side of a cloud is much stronger than on the far side. That difference, called a tidal force, can stretch a cloud apart before it collapses, which is why astronomers have long wondered how young stars could form so close to one. Pairs of stars are common across the galaxy, so counting how many survive near a black hole is a clue to where they were born.