With the help of NASA’s Hubble Space Telescope, scientists have discovered for the first time an isolated stellar-mass black hole, heading toward the bulge at the center of the Milky Way.
An international team of astronomers has managed to detect a single “isolated” black hole wandering through interstellar space less than 5,200 light-years away in the constellation Sagittarius. The exciting discovery, which has not yet been peer-reviewed, has been uploaded to the arXiv preprint server.
Detecting black holes alone from Earth is an impossible task for many. And it is that unless they manage to trap some passing matter in their gravitational field, they are basically invisible.
Thus, black holes can only be seen when they interact with other objects and observe their effects on the surrounding space, such as companion stars. A black hole’s gravitational field is so extreme that it warps and twists any light that might travel through it.
How did they do it?
To find the elusive black hole, the researchers turned to a technique known as “astrometric microlensing,” which uses the fact that a mass moving through space can act as a gravitational lens. This lensing distorts both the brightness and, above all, the apparent position of the stars along the observer’s line of sight beyond the mass itself.
Previous microlensing events have made it possible to detect exoplanets and stars too faint to see.
To confirm the presence of the black hole, astronomers used NASA’s Hubble Space Telescope and several ground-based observatories. Arriving at their finding took them ten years of observations.
According to experts, the finding could contribute to a complete census of the black hole population and to the understanding of the formation and evolution of stellar-mass black holes.
“Isolated Black Holes Exist”
“Now we know that isolated black holes exist,” Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, who led the team that made the discovery, told Space.com. “And they have masses similar to black holes found in binaries. And there must be a lot of them out there.”
“If the bending of light caused by these massive objects can be detected and measured, it is possible to detect them and measure their masses,” Sahu said.
As reported by the scientific media, the researchers estimated that this isolated black hole had a mass 7.1 times greater than that of the Sun. They also discovered that this black hole moves at a speed of 162,000 km/h. This suggests that this black hole may have received a “kick” from the supernova explosion that gave rise to it.