Two international teams of scientists, including astronomers from the Astronomical Observatory of the University of Warsaw, have announced the discovery of a free-floating black hole in the Milky Way galaxy. This is the first detection of its kind.
The existence of black holes in the Milky Way has been discovered thanks to many years of observations carried out under the OGLE project, which is conducted by the University of Warsaw.
Scientists from the OGLE project observed the gravitational microlensing phenomenon, designated OGLE-2011-BLG-0462, on June 2, 2011, while it was also recorded by the New Zealand-Japan MOA project.
“When we detected the brightening, which was undoubtedly by gravitational microlensing, we did not anticipate that this would be a breakthrough discovery. Now, the event became the jewel in the crown of over 20 thousand microlensing events discovered by us,” Prof. Andrzej Udalski from the Warsaw University Astronomical Observatory says.
According to the Astronomical Observatory of the University of Warsaw:
In the second half of 2011, when it was clear that the event timescale is relatively long (and so the lensing object could be massive), a team of astronomers led by Prof. Kailash Sahu (Space Telescope Science Institute) has initiated observations of the event with the Hubble Space Telescope (HST), allowing them to precisely measure the position of the object in the sky. These observations were supplemented in 2021 with additional measurements taken with the HST by another team led by a PhD candidate Casey Lam and Prof. Jessica Lu (University of California, Berkeley). The analysis of photometric and astronometric measurements was performed independently by the two teams.
As Dr Przemysław Mróz, a member of the OGLE project, said the result of the modelling indicated that the event OGLE-2011-BLG-0462 had been caused by an object several times more massive than the Sun. “A light of an ordinary star of that mass would have been easily detected, so the lensing object must be a free-floating stellar-mass black hole,” he adds.
The discovery of the first isolated black hole in the Milky Way is a breakthrough and opens a new path for detecting these rare objects.
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