Closest-known black hole to Earth discovered; lies just 1600 light-years away

Astronomers using the Gemini North telescope in Hawai'i, operated by NSF's NOIRLab, have discovered a stellar-mass black hole in our cosmic backyard. It is the closest-known black hole to Earth - three times closer to Earth than the previous record holder, which is an X-ray binary in the constellation of Monoceros.

This newly-discovered black hole is about 10 times more massive than our Sun and is located about 1600 light-years away in the constellation Ophiuchus.

The team discovered this black hole by making exquisite observations of the motion of the black hole's companion, a Sun-like star that orbits the black hole at about the same distance as the Earth orbits the Sun. They originally identified the system as potentially hosting a black hole by analyzing data from the European Space Agency's (ESA's) Gaia spacecraft.

"While there have been many claimed detections of systems like this, almost all these discoveries have subsequently been refuted. This is the first unambiguous detection of a Sun-like star in a wide orbit around a stellar-mass black hole in our Galaxy," explained Kareem El-Badry, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian and the Max Planck Institute for Astronomy, and the lead author of the paper describing this discovery.

Using the Gemini Multi-Object Spectrograph instrument on Gemini North, El-Badry and his team explored the system in more detail. It provided precise measurements of its orbital period while follow-up observations allowed the team to identify the central body as a black hole roughly 10 times as massive as our Sun.

"While this potentially augurs future discoveries of the predicted dormant black hole population in our Galaxy, the observations also leave a mystery to be solved - despite a shared history with its exotic neighbor, why is the companion star in this binary system so normal?" said NSF Gemini Program Officer Martin Still.