Nov 4, 2022 - Science

Astronomers find the closest black hole to Earth yet

Animated illustration of a magnifying glass focusing on a black hole.

Illustration: Eniola Odetunde/Axios

Scientists have found the closest black hole to Earth yet.

Why it matters: The black hole is located about 1,600 light-years away, and it could help scientists learn more about the formation and evolution of these extreme objects.

  • Scientists estimate there are 100 million black holes in the Milky Way that are 5–100 times more massive than the Sun.

What they found: The black hole, named Gaia BH1, is thought to be 10 times more massive than our Sun.

  • But Gaia BH1 is different from other black holes that feed off their companion stars. Instead, this black hole and its star are quietly hanging out together in their part of space.
  • Other black holes found of this size pull in matter from the stars that orbit them and emit bright X-rays.
  • "While there have been many claimed detections of systems like this, almost all these discoveries have subsequently been refuted," astrophysicist Kareem El-Badry an author of a study about this discovery set for publication in the Monthly Notices of the Royal Astronomical Society, said in a statement. "This is the first unambiguous detection of a Sun-like star in a wide orbit around a stellar-mass black hole in our Galaxy."

How it works: The team of researchers originally found the black hole in data from the Gaia spacecraft by tracking the movements of its stellar companion.

  • They then followed up with observations from the Gemini North telescope in Hawaii, allowing scientists to confirm the system looks like it's composed of a black hole and a star.

The intrigue: It's not actually clear how the Gaia BH1 system formed.

  • The star that collapsed and gave rise to the black hole had to have been about 20 times more massive than the Sun, only living for a few million years, according to the new research.
  • As the large star died on its way to becoming a black hole, it should have expanded, enveloping its companion star relatively early in its life before it could mature into a Sun-like star, but that didn't happen.
  • "It is not at all clear how the solar-mass star could have survived that episode, ending up as an apparently normal star, as the observations of the black hole binary indicate," NSF’s NOIRLab wrote in a release. "Theoretical models that do allow for survival all predict that the solar-mass star should have ended up on a much tighter orbit than what is actually observed."
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