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Astronomy and space

Astronomy and space

Astronomers discover nearest black hole to Earth – so far

06 May 2020 Tami Freeman
HR 6819 triple system
Artist's impression showing the orbits of the objects in the HR 6819 triple system: an inner star and a star in a wider orbit (orbits in blue), and the newly discovered black hole (orbit in red). (Courtesy: ESO/L Calçada)

Astronomers have found the nearest black hole to Earth known to date – situated just 1000 light-years away.

The newly-discovered black hole is part of a triple system that includes an inner binary – one star and its unseen companion in a circular orbit – plus another star in a wider orbit. Located in the constellation of Telescopium, this triple system is so close to us that its two stars can be viewed from the southern hemisphere with the naked eye.

The team originally thought that the system, known as HR 6819, only contained the two stars. However, observations from the MPG/ESO 2.2-metre telescope at the European Southern Observatory’s La Silla Observatory revealed evidence for a third, invisible, object: a black hole. The researchers detected the black hole and calculated its mass by studying the orbit of the star in the inner pair. They found that the objects in this inner pair have roughly the same mass, with the star orbiting the black hole every 40 days.

Unlike most other black holes found in our galaxy (a couple of dozen to date), the hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that does not interact violently with its environment and, therefore, appears truly black.

Scientists estimate that many more stars in the Milky Way’s lifetime will have collapsed into black holes as they ended their lives. The discovery of this silent, invisible black hole in HR 6819 provides clues about where these other hidden black holes may be. The team say that, now they know what to look for, many more similar black holes could be found in the future.

The findings were published today in Astronomy & Astrophysics.

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