Black hole near the earth: "Tip of an exciting iceberg" - accompanying stars are visible

Astronomers discovered a black hole near Earth by accident - its companion stars are even visible to the naked eye.

• Astronomers have a black hole discovered that only 1,000 light-years from Earth away
• The two companion stars of the black hole are visible to the naked eye
• The HR 6819 system could be an indication that there many undiscovered black holes are

Black holes are generally considered to be mysterious places that are far from the earth and cannot be seen with the naked eye - because no light comes out of them. However, researchers have now discovered a black hole with its companion stars so close to Earth that the stars are visible to the naked eye.

There is only 1,000 light years between the earth and the HR 6819 system . Whereby "close to earth" is relative: In astronomical dimensions, the 1000 light-years distance between the newly discovered black hole and the earth is not much - in humanly understandable dimensions, the distance is gigantic: a light year denotes the distance that sunlight is in one year: 9.46 trillion kilometers.

1/4 A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1000 light-years from Earth.https: //t.co/7zHzePwvS9

Illustration credit: @ESO / L. Calçada pic.twitter.com/YDmYD2sq4T

Newly discovered black hole is only 1,000 light years from Earth

A group of astronomers discovered the black hole when its two companion stars followed with a telescope at the La Silla Observatory of the European Southern Observatory (ESO) in Chile - actually as part of a study of binary star systems . “We were completely surprised to find that this is the first star system with a black hole that can be seen with the naked eye ,” said Petr Hadrava, who co-authored the research. Further observations showed that one of the two visible stars orbits an invisible object every 40 days. The second star is a long distance from this couple. 

The newly discovered black hole in the HR 6819 system is one of the first found black holes with stellar mass that do not interact violently with their surroundings and therefore appear really black. Most of the black holes discovered so far reveal their presence through the release of strong X-rays. However, after noticing the presence of the invisible black hole , the researchers were able to calculate its mass: To do this, they examined the orbit of the inner star. "An invisible object with a mass that is at least four times the size of the sun can only be a black hole ," concludes study leader Thomas Rivinius.

Astronomers suspect: Are there more black holes in the Milky Way?

So far, astronomers have only discovered a few dozen black holes in our galaxy. However, scientists estimate that there could be many more stars in the Milky Way that collapsed into black holes at the end of their lives . "There have to be hundreds of millions of black holes, but we only know of very few," explains Rivinius. "If we know what to look for, we should be better able to find it," continued the researcher. His colleague, co-author Dietrich Baade, assumes that we only see "the tip of an exciting iceberg".

The researchers' discovery could already reveal a second system with a black hole , astronomers believe. "We realized that another system, called LB-1, could also be such a triple system ," explains co-author Marianne Heida. However, the astronomers would need more observations to be able to say that for sure.

Does the newly discovered black hole lead to further discoveries?

"LB-1 is a little further away from Earth, but is still fairly close astronomically, which means that there are likely to be many more of these systems," added Heida. The astronomers hope that the discovery of such systems with black holes shed light on the formation and evolution of stars who gave their lives with more than eight solar masses start and in a supernova explosion end that a black hole leaves.

System HR 6819 can be seen with the naked eye - just not the black hole itself

The HR 6819 system can be observed from the southern hemisphere: It is located in the constellation Telescopium , the stars can be seen in a dark night without binoculars or a telescope. Only the black hole itself cannot be spotted - not even with a telescope or binoculars. "This system contains the black hole closest to Earth that we know of," study director Rivinius explains. The study was published in the journal "Astronomy & Astrophysics".

Black holes are a popular area of ​​research

Black holes are a popular area of ​​research in astronomy and astrophysics . For example, researchers have observed the black hole in the center of the Milky Way . Suddenly the black hole called Sagittarius A * became voracious and shone brightly. They watched another black hole tear a star apart - an extremely brutal event. In addition, researchers have discovered an extremely rare phenomenon: three black holes are about to merge.

There is controversy in research about an “impossible” black hole. Is it really something completely different? However, researchers are certain of one thing: they have discovered the black hole with the largest mass known to date in the galaxy cluster “Abell 85”.

By Tanja Banner

Rubric list picture: © ESO / L. Calçada