Earth's closest Black Hole discovered at a hair's breadth of just 1000 Light Years!

Astronomers at ESO's La Chille Observatory in Chile, have found a black hole at a meagre 1000 light years from the Earth, making it the closest black hole to our solar system ever known.

This newfound dark neighbour, is at least 4.2 times as massive as the sun, and lives with two ordinary stars whose funny orbits gave the black hole's presence away. Located in the southern constellation of Telescopium, the black hole is a part of a Triple System called HR 6819.

Being just 1000 light years away, the system is so close that it can be observed on the southern sky by the naked eye, without the aid of a telescope or a binocular. 

"We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye," ---- Petr Hadrava, a scientist emeritus at the Academy of Sciences of the Czech Republic in Prague and co-author of the study, said in the statement.

This wide-field view shows the region of the sky, in the constellation   Telescopium where HR 6819 is located.

(Image credit: ESO/Digitized Sky Survey 2/Davide De Martin)

The Discovery of the Black Hole :

Astronomers discovered this black hole while studying what they thought was just an ordinary binary star system, or two stars that orbit a common center of mass. The astronomers were using the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile to observe the binary, as part of a broader study on double star systems. But furthur analysis on the observations revealed the presence of another masked entity : The Black Hole.

This artist's impression shows the orbits of the objects in the HR 6819 triple system, which consists of a binary star pair in which one star (orbit in blue) orbits a black hole (orbit in red), as well as another star with a wider orbit (also in blue). (Image credit: L. Calçada/ESO)

Although the astronomers could not directly observe the black hole, they were able to infer its presence based on its gravitational interactions with the other two stars in the Triple system . By observing the system for several months, they were able to map out the stars' orbits and figure out that another massive, unseen object must be acting in the system, evidently : a black hole.

One of the star in the system have been observed to show a period of 40 days around the invisible object, while the other orbits at a much larger distance from the black hole.

The black hole has been determined to be a stellar-mass blackhole (a blackhole formed by the gravitational collapse of a star).

This black hole, however, is being speculated to be somewhat "Unusual".

“The hallmark of this black hole is that it is truly black,” said Dietrich Baade, an emeritus astronomer at European Southern Observatory (ESO) and a co-author of the study . “Almost all the other black holes that we know are in the Milky Way – and there are only two dozen of them – shine very brightly in X-rays. " he added.

Baade explained that the other blackholes had a companion star that feeds them with gas, leading to the above phenomenon. 

He further added that the stars in this system  are not so massive as to lose a lot of gas and therefore the black hole is starving and that is what makes it so "dark".

How to observe HR 6819? :

Being just 1000 light years away, HR 6819 is visible in the Southern Hemisphere through the naked eye. This provides the ordinary population an overwhelming opportunity to observe this astronomical wonder.

The system appears as a single, fifth-magnitude star in the modern constellation of Telescopium, near the border with the constellation of Pavo, the peacock, observation on a clear night sky in the southern hemisphere of the Earth. 

The HR 6819 triple system, which consists of two stars and a black hole, is located in the modern constellation of Telescopium, which is visible from the  Southern Hemisphere. The fifth-magnitude stars are bright enough to see  without binoculars or a telescope under a clear, dark sky. 

 (Image credit: SkySafari)

  

On the magnitude scale , in which smaller numbers denote brighter objects, the faintest objects visible to the human eye are at magnitude 6.5. Currently shining at magnitude 5.4 — just slightly brighter than Uranus , the dimmest visible planet — HR 6819 is just barely bright enough for our eyeballs.