Click for original image.

Using both archival data from the Hubble Space Telescope and infrared data from the Webb Space Telescope, astronomers think they have identified the first black hole ever found inside the globular cluster Omega Centauri.

The image to the right, reduced to post here, was taken by the Hubble Space Telescope and shows the globular cluster, the largest such object in the Milky Way, with an estimated 10 million stars packed into a space only 150 light years across. It is located about 17,000 light years away. Previous research had suggested it held at least one intermediate-sized black hole within it, with models suggesting another 10,000 stellar-mass black holes. Now scientists think they have found the first of the latter group, indicated by the red circle in the inset.

By sifting through more than 20 years of Hubble archival data and pulling in recent Webb data to further refine their astrometric measurements, the team located a star orbiting an invisible object so hefty that it has to be a black hole. Dubbed oMEGACat BH-2, it is the first stellar-mass black hole detected in Omega Centauri, and it has some surprising qualities. oMEGACat BH-2 has a lower-than-expected mass and, with its visible star companion, the black hole-star duo has the longest orbital period of any black hole binary system known to date.

The star orbits the black hole every 94 years. The long orbit suggests to the scientists that these objects did not form together but were captured because of the crowded nature of Omega Centauri. The scientists also believe that crowded nature will likely cause them to break free of each other, sometime in the future.

There are innumerable uncertainties and questions remaining. First, the detection needs confirmation. Second, where are the thousands of other expected stellar-mass black holes? And where is that predicted intermediate-sized one? Moreover, though astronomers believe the halo of the Milky Way’s 158 known globular clusters mark the very early history of the galaxy, much of that history remains unsettled.