An unseen intermediate-mass black hole lurks at the heart of the nearest globular star cluster to Earth, 6,000 light-years away, astronomers have discovered.

Intermediate-mass black holes, weighing about 100 to 100,000 times the mass of the Sun, appear to be rare, and astronomers have spotted some possible such black holes at the periphery of other galaxies, as well as in dense globular star clusters orbiting the Sun. our galaxy.

Using the unique capabilities of the NASA/ESA Hubble Space Telescope, astronomers focused on the core of the globular star cluster Messier 4 (M4) to probe black holes with greater precision than previous surveys. Their study is published in the Royal Astronomical Society’s journal Monthly Notices.

The team, led by Eduardo Vitral from the Space Telescope Science Institute in Baltimore, identified a possible intermediate-mass black hole, weighing about 800 times the mass of the Sun.

This hole is not visible, but its mass was calculated by studying the motion of the stars in its gravitational field. Specifically, the astronomers looked at twelve years of Hubble observations of M4. The European Space Agency’s (ESA) Gaia spacecraft also contributed scans of over 6,000 stars that constrained the cluster’s overall shape and mass.

However, because intermediate-mass black holes in globular clusters are so elusive, Vitral warns that “alternatively, there may be a stellar mechanism that we just don’t know about, at least in the context of current physics.”