At the heart of our Milky Way galaxy lies a supermassive black hole, Sagittarius A, a staggering 23.5 million kilometers in diameter and situated approximately 27,000 light-years from Earth.
In a groundbreaking discovery, a team of astronomers led by Florian Peißker from the University of Cologne has identified a binary star system, known as D9, orbiting this enigmatic black hole.
The findings, published in Nature Communications, provide critical insights into the extreme environment at the galaxy’s core and help solve the puzzle of hypervelocity stars.
Binary star systems consist of two stars gravitationally bound to each other, orbiting a common center of mass. While our Sun is a solitary star, about one-third of the stars in the Milky Way belong to binary or multiple-star systems. These systems offer astronomers valuable data, such as the masses of stars, inferred through their orbital speeds and distances.
Although binary star systems near supermassive black holes have long been theorized, this is the first confirmed detection. Using the European Southern Observatory’s Very Large Telescope, researchers identified the binary system by analyzing the shifting starlight caused by the Doppler effect. This revealed a characteristic "wobble" in the light, indicative of orbital motion.
The D9 system is estimated to be 2.7 million years old, with its stars likely forming far from the black hole before migrating to its vicinity. Surviving about a million years in such a volatile environment provides clues about the black hole's disruptive capabilities and its influence on celestial bodies.
The discovery sheds light on hypervelocity stars — rare, fast-moving stars traveling at speeds exceeding 1,000 kilometers per second. These stars are believed to originate from binary systems disrupted by supermassive black holes.
The theory suggests that when a binary system ventures too close to a black hole, the gravitational forces create a chaotic interaction. One star may be captured by the black hole, while the other is ejected at incredible speeds, hurtling through the galaxy as a hypervelocity star.
Since 2005, astronomers have identified around 20 hypervelocity stars, most of which appear to be fleeing the galactic center, supporting this theory. The discovery of D9 strengthens the connection between binary stars and the formation of hypervelocity stars, providing a crucial piece to the puzzle.
This discovery not only confirms the existence of binary star systems near Sagittarius A but also enhances our understanding of the dynamic processes at play in the galactic center. By studying these systems, scientists can unravel the mysteries surrounding black holes, stellar interactions, and the formation of high-speed stars.
For astronomy enthusiasts, locating Sagittarius A in the night sky is possible with the help of a good stargazing app or by finding the bright red star Antares in Scorpio and following the constellation’s tail.