Hidden black hole found in nearby galaxy

(ORDO NEWS) — A team of astronomers known as the “black hole police” have repeatedly disproved the discovery of “silent” stellar-mass black holes, but now they have found one themselves.

Some calculations predict that as many as one hundred million stellar-mass black holes may be hiding in our galaxy. However, this is not known exactly: so far only a couple of dozen of them have been found.

The problem is that such objects manifest themselves only if they actively absorb matter, throwing out X-ray fluxes. Most black holes hardly interact with the environment and remain practically invisible.

This makes scientists look for them with particular passion, and reports of the discovery of such hidden black holes have been published more than once.

However, all these findings have been refuted over and over again. A team of astronomers led by Tomer Shenar plays an active role in such denials, earning them the nickname “black hole police.”

It is all the more surprising that now it is this group that has announced the discovery of a new candidate for a “sleeping” black hole, the most reliable of all.

Scientists relied on the method of radial velocities, which has proven itself in the search for distant exoplanets: if an invisible neighbor rotates around a star, it can be seen by the weak oscillations of the star caused by its attraction.

If the mass of the object turns out to be large enough, more than 2.2 solar masses, then we can assume that this is a black hole – or a second star, the light of which is mixed with the light of the first.

However, at vast distances, a pair of stars can merge into one source, and it is extremely difficult to distinguish between both.

Hidden black hole found in nearby galaxy 2
Tarantula Nebula

Shenar and his colleagues use a spectral disentanglement algorithm to do this, which selects binary stars of such spectral characteristics that together they create a spectrum that is observed by telescopes.

In certain cases, the algorithm may indicate that one of the participants in the tandem does not radiate, representing a black hole.

It was this algorithm that refuted some past discoveries, bringing scientists the fame of the “black hole police”. However, now he has helped to find a new and very promising candidate.

For six years, astronomers have tracked the angular velocities of about 1,000 massive stars in the Tarantula Nebula , which is located in a small satellite galaxy of the Milky Way, the Large Magellanic Cloud.

Observations were made with the VLT telescope of the Southern European Observatory (ESO). Special attention of scientists was attracted by the star VFTS 243, gaining 25 solar masses.

Judging by the weak fluctuations, it revolves around an invisible object, making a complete revolution in 10.4 of our days.

The “unraveling the spectrum” algorithm indicated that this object is a black hole with a mass of nine times the mass of the Sun.

It is believed that such black holes remain after supernova explosions, as a result of the collapse of the cores of massive stars, while their outer shells are scattered around the neighborhood.

However, no remnants have been observed near VFTS 243. This may indicate a hypothetical alternative way for the formation of stellar-mass black holes – a direct and complete collapse, without an explosion and loss of outer shells.


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