The first black hole in a triple system: the discovery baffles researchers

Until now, researchers have only known that black holes exist in binary systems, that is, orbited by a single star. Now physicists from MIT and Caltech have almost accidentally discovered a black hole in a triple system for the first time.

A surprise in a well-studied star system

Coincidentally, because the V404 Cygni star system, 8,000 light-years from Earth, and its black hole are already well researched. However, until now it was assumed that a single star would orbit the black hole at a short distance and be slowly swallowed.

Now researchers have discovered another star, much more distant. As MIT Tech reports. Instead of 6.5 days like the first, the second star needs 70 thousand years to orbit the black hole.

A star at a great distance from the black hole

According to calculations by researchers led by Kevin Berridge of the MIT Department of Physics, the exoplanet should be 3,500 astronomical units away from the other two celestial bodies. The astronomical unit (AU) is equivalent to the distance between the Earth and the Sun, which is approximately 150 million kilometers.

Given this great distance, researchers wondered whether the third star actually belonged to the system. A positive answer was made possible thanks to analyzes of images taken from the European Space Agency's Gaia space telescope, which has accurately recorded all the movements of all the stars in this galaxy since 2014.

The result: with almost 100% certainty, it is a triple system, and therefore the first of its kind in celestial observation. “We see two stars following each other because they are connected by a weak gravitational chain,” Burdge says.

The mystery of black hole formation

This realization raises the following question, to which there is no sure answer. How could a black hole form without breaking the weak connection with the outer star, knocking it out of the system?

Therefore, a supernova is out of the question, as many simulations have shown. The simplest solution to this puzzle is that the black hole formed through what is called a soft collapse. Massive stars will collapse to form a black hole without an explosion. As heise.de writes.

The Tertiary system is about 4 billion years old

The next question for researchers is whether there are other triple systems in the universe. In any case, the age of the first system discovered so far consisting of two stars and a black hole has been clarified. This is said to have originated about four billion years ago.

Physicists from MIT and Caltech have the results of their research Published in Nature magazine.