Scientists have made an unprecedented discovery in our galaxy—the largest stellar black hole ever detected. Named Gaia BH3, this colossal black hole is believed to be approximately 33 times larger than our Sun. Its presence was stumbled upon when astronomers analyzing data from the European Space Agency's Gaia mission observed an unusual wobbling motion in a star located in the constellation of Aquila.

The unexpected jiggling of the star was soon understood to be caused by its orbit around the massive black hole, Gaia BH3. "No one was expecting to find a high-mass black hole lurking nearby, undetected so far," remarked study author Pasquale Panuzzo, an astronomer at the Observatoire de Paris.

Situated approximately 2,000 light years away from us, Gaia BH3 is now recognized as the second-closest known black hole to our solar system. Significantly larger than its predecessor, Cygnus X-1, which had a mass 21 times that of the Sun, Gaia BH3 dominates the record of the most enormous stellar black holes. In fact, most other stellar black holes in our galaxy do not exceed 10 times the mass of our Sun.

Stellar black holes are a type of black hole that develops from the remnants of massive stars. When these massive stars deplete their hydrogen fuel, they collapse under their own gravity, resulting in a supernova explosion. What is left behind is the massive core of the star. If the core is sufficiently massive, it collapses into a black hole, an exceptionally dense astronomical entity that even light cannot escape from.

Although this newly discovered black hole is the largest of its kind in our galaxy, it is still much smaller than the supermassive black hole Sagittarius A*, which resides at the center of the Milky Way. Supermassive black holes are millions to billions of times the mass of the Sun and are commonly found at galaxy centers.

The star that orbits Gaia BH3 provides valuable insights into the progenitor star that gave rise to the black hole. Binary stars often share similar compositions, and data from the European Southern Observatory's Very Large Telescope, utilizing the Ultraviolet and Visual Echelle Spectrograph instrument, revealed that the companion star is extremely metal-poor. This suggests that the parent star of the black hole was also metal-poor. Metal-poor stars, composed primarily of hydrogen and helium with minimal heavier elements, are believed to retain more mass throughout their lifetimes, potentially providing enough material for the formation of massive black holes.

However, direct evidence connecting metal-poor stars to the creation of high-mass black holes has been scarce until now. The ongoing investigation of this black hole and its star is expected to yield additional valuable data, with a comprehensive release planned for 2025.

Elisabetta Caffau, a researcher at CNRS Observatoire de Paris and co-author of the paper, highlighted the uniqueness of this discovery, stating, "We took the exceptional step of publishing this paper based on preliminary data ahead of the forthcoming Gaia release because of the unique nature of the discovery."

As astronomers continue to unravel the secrets of Gaia BH3 and its orbiting star, this groundbreaking finding offers an extraordinary glimpse into the formation and characteristics of stellar black holes.