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Astronomers have discovered聽a black hole聽with a mass about 33 times greater than that of our sun, the biggest one known in the Milky Way aside from the supermassive black hole lurking at the聽center of our galaxy.

The newly identified black hole is located about 2,000 light-years from聽Earth聽鈥撀爎elatively close in cosmic terms 鈥撀爄n the constellation Aquila, and has a companion star orbiting it, researchers said on April 16. A light year is the distance light travels in a year, 5.9 trillion miles.

Black holes are extraordinarily dense objects with gravity so strong that not even light can escape, making it difficult to spot them. This one was identified through observations made in the European Space Agency鈥檚 Gaia mission, which is creating a huge stellar census, because it caused a wobbling motion in its companion star. Data from the European Southern Observatory鈥檚 Chile-based Very Large Telescope and other ground-based observatories were used to verify the black hole鈥檚 mass.

鈥淭his black hole is not only very massive, it is also very peculiar in many aspects. It is really something we never expected to see,鈥� said Pasquale Panuzzo, a research engineer at the French research agency CNRS working at the Paris Observatory聽and lead author of the study published in the journal聽Astronomy & Astrophysics.

For instance, the black hole, called Gaia BH3, and its companion are traveling within the galaxy in the opposite direction of how stars typically orbit in the Milky Way.

Gaia BH3 probably formed after the death of a star that was more than 40 times as massive as the sun, the researchers said.

Black holes that result from the collapse of a single star are called stellar black holes. Gaia BH3 is the largest-known stellar black hole, according to astronomer and study co-author Tsevi Mazeh of the Tel Aviv University in Israel.

Stellar black holes are dwarfed in size by the supermassive black holes inhabiting the center of most galaxies. One such black hole called Sagittarius A*, or Sgr A*, is located at the heart of the Milky Way. It possesses 4 million times the mass of our sun and is located about 26,000 light-years from Earth.

Gaia BH3鈥檚 progenitor star was composed almost entirely of hydrogen and helium. Stars in the early universe had such a chemical composition, known as low metallicity. This star had formed relatively early in the universe鈥檚 history 鈥撀爌erhaps 2 billion years after the Big Bang event.

When that star exploded at the end of its lifespan 鈥撀燾alled a supernova 鈥撀爄t blasted some material into space while the remnant violently collapsed to form a black hole.

The discovery of Gaia BH3, according to Mr. Panuzzo, supports stellar evolution models showing that massive stellar black holes can be produced only by a low metallicity star like this one鈥檚 progenitor star.

Gaia BH3鈥檚 companion star, just as old as the other one was, is about 76% of the mass of the sun and a bit colder, but around 10 times more luminous. It orbits the black hole on an elliptical path at a distance varying between about 4.5 times the distance between Earth and the sun 鈥撀燼 measure called an astronomical unit (AU) 鈥撀燼nd 29 AU. By way of comparison,聽Jupiter聽orbits around five AU from the sun and聽Neptune聽around 30 AU.

鈥淭he surprising result for me was the fact that the chemical composition of this companion star does not show anything special, so it was not affected by the supernova explosion of the black hole,鈥� Observatoire de Paris astronomer and study co-author Elisabetta Caffau said.

This story was reported by Reuters.