'Stellar-Mass Black Hole' Discovered for the First Time in the Giant Star Cluster Omega Centauri

Explanation

A 'stellar-mass black hole' has been discovered for the first time inside Omega Centauri, the largest 'globular cluster' in the Milky Way galaxy. The finding combines more than 20 years of observations by the Hubble Space Telescope with the latest data from the James Webb Space Telescope (JWST).

Because black holes emit no light at all, they cannot be observed directly. So how was it found? The key lies in 'the motion of the surrounding stars.' A certain star (with a mass about 0.78 times that of the Sun) was found to be orbiting under the pull of the gravity of something invisible, and calculating its orbit revealed that the companion is a black hole with a mass about 4.46 times that of the Sun. The orbital period is roughly 94 years, the longest period yet found among known black hole binaries.

What is being applied here are the concepts of 'universal gravitation' and 'Kepler's laws,' which are taught in high school physics. If a star's orbit (its period and size) is known, the mass of an invisible object can be calculated — the fact that an object's true nature can be deduced from its motion, even without seeing it directly, is one of the great strengths of physics.

NASA plans to launch the new Nancy Grace Roman Space Telescope in August 2026, and more of these 'hidden black holes' are expected to be discovered as a result.