The black hole wandering in our galaxy

A gravitational microlensing was the clue to detect it. What did this team of researchers find for the first time? They found the black hole wandering in our galaxy. It travels freely just over 5,100 light-years away from Earth. The finding has just been made public in an article in ‘ArXiv’.

The black hole wandering in our galaxy was discovered by a peculiar alignment.
The black hole wandering in our galaxy was discovered by a peculiar alignment.

Unpublished encounter

A gravitational microlens is a rare phenomenon. How does it occur? When a very bright light source (a star or quasar) aligns with a massive, compact object (the microlens). The path of the star’s light is deflected due to the object’s gravity. This bending of the light acts as a ‘cosmic magnifying glass’. It magnifies dark objects. Therefore, it helps to discover very faint bodies in the sky such as neutron stars or black holes.

No one had ever managed to find any. That is due to the very nature of these bodies. Not even light escapes their powerful gravitational fields. They are black objects moving through the black background of space. It is almost impossible to detect them.

Direct observational methods, for the reasons explained above, are ruled out. Therefore, astronomers have resorted to looking for their gravitational lensing effects. They are not easy to observe even with the most powerful telescopes. This time luck favored two teams of astronomers. Using the Hubble Space Telescope, they saw a star shine brighter than it should for no apparent reason.

The Hubble space telescope facilitated the discovery.
The Hubble space telescope facilitated the finding.

Hidden traveler

For six long years they analyzed the light variations of the star. They saw something else: the position of the star seemed to change. It could only be due to an invisible, moving object ‘bending’ the star’s light. They had found an interstellar black hole.

It is the first one to be ‘hunted’ floating freely among the stars of our galaxy. Researchers have even managed to estimate its mass. They believe it is seven times that of the Sun. It travels at a speed of about 45 km/s.

The black hole wandering in our galaxy brings implications. From now on we will have to be on the lookout, as there must be others. And if they come close to a star, they will change its destiny forever.

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