With a new method: closest black hole detected

Black holes do not only fascinate experts.

With a new method: closest black hole detected

Black holes do not only fascinate experts. The most recent discovery of such is not even 1600 light-years away from Earth and is thus the closest to the home planet.

At a distance of less than 1600 light-years from Earth, scientists have discovered a candidate for the closest black hole to date. The object orbits a star in the constellation Ophiuchus, which resembles our sun, they report in the journal "Monthly Notices of the Royal Astronomical Society". There is no plausible astrophysical scenario "that can explain the orbit and is not related to a black hole". With the new method used, the team hopes to make more such discoveries in the coming years.

Black holes have mass concentrated in an extremely small volume. Supermassive versions are likely to be found at the centers of all major galaxies, as the scientists led by Kareem El-Badry from the Max Planck Institute for Astronomy in Heidelberg and the Harvard-Smithsonian Center for Astrophysics in Cambridge explain.

Black holes with stellar mass - about five to a hundred times the mass of the Sun - are much more common. There are an estimated 100 million of them in the Milky Way alone - only a few have been confirmed so far. These are usually active objects that glow brightly in X-ray light. The black hole that has now probably been discovered, however, is dormant - and therefore much more difficult to discover.

The researchers used data from the European Space Agency (ESA)'s "Gaia" space probe, and targeted measurements with telescopes were also used. Tiny shifts in the star's position revealed the presence of the companion object. The black hole "Gaia BH1" is less than half as far away as the closest known such object, it said. It has a mass of around ten solar masses and orbits the sun-like star with an orbital period of 185.6 days and about the average distance between Earth and the Sun.

The "Gaia" astrometry mission is designed for high-precision measurements of star positions. Where two objects orbit each other, each usually describes a small ellipse in the sky. With the orbital data of so-called binary star systems, the scientists specifically searched for candidates for a black hole.

"Although there have been many alleged discoveries of such systems, almost all of them were later refuted," El-Badry explained. "This is the first clear detection of a sun-like star in a wide orbit around a stellar-mass black hole in our galaxy," he says. A light-year is the distance that light travels in a vacuum in one year: 9.46 trillion kilometers.

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