For the first time, astronomers have confirmed the existence of a black hole drifting alone in space—without a companion star.
This exciting discovery was made by a team at the Space Telescope Science Institute, along with researchers from the University of St Andrews and the European Southern Observatory.
Their findings were recently published in The Astrophysical Journal.
The story began in 2022, when this group of scientists reported spotting a mysterious “dark object” moving through the constellation Sagittarius.
They believed it might be a black hole traveling through space on its own.
But another team of researchers quickly challenged that idea, suggesting it could actually be a neutron star—a much smaller and less massive object left behind after a star explodes.
Black holes are incredibly hard to detect unless they are part of a binary system, where they orbit a nearby star.
In those cases, astronomers can spot them by looking at how they affect the light from their companion star.
But finding a black hole that’s entirely alone is much more difficult. In this case, the black hole was only noticed because it briefly passed in front of a distant star. This event caused the background star’s light to brighten and slightly shift position—an effect known as gravitational microlensing.
The team originally based their discovery on data from the Hubble Space Telescope collected between 2011 and 2017. Now, they’ve added more recent data from Hubble in 2021 and 2022, along with measurements from the Gaia space probe.
With this new information, they were able to confirm that the object is around seven times the mass of our sun—too heavy to be a neutron star. That leaves a black hole as the only explanation.
Interestingly, the group that originally disagreed with the black hole theory has since updated their own analysis. In 2023, they also concluded the object is most likely a black hole, with a mass close to six times that of the sun. Although there’s some uncertainty in their measurement, it still supports the black hole idea.
This newly confirmed discovery marks the first time scientists have identified a black hole that isn’t paired with another star.
The team hopes this is just the beginning. With the launch of the Nancy Grace Roman Space Telescope in 2027, they expect to find many more of these “invisible” wanderers moving silently through space.
Source: KSR.
