GARCHING, Germany — Astronomers discovered the fastest known star in the Milky Way, a celestial body traveling at 25,000 kilometers per second as it loops around the supermassive black hole at the center of our galaxy.
The star, designated S301, was detected using the Very Large Telescope Interferometer (VLTI) at the European Southern Observatory's Paranal Observatory in northern Chile. Researchers published their findings in the journal Nature, noting that the star's extreme proximity and velocity relative to Sagittarius A* provide a rare laboratory for testing Albert Einstein's theory of general relativity. Reinhard Genzel, director of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and a 2020 Nobel laureate, stated that tracking stars near the galactic core opens unprecedented windows into the fundamental properties of space-time under extreme gravitational fields.
Orbital Mechanics and Extreme Velocity
S301 completes a tight orbit around Sagittarius A* every 8.7 years. At its closest approach, the star comes within 12 times the distance between the Earth and the Sun, reaching speeds of approximately 25,000 kilometers per second—about 8% of the speed of light. Felix Mang, a doctoral student at the Max Planck Institute and co-author of the study, explained that stars cannot form naturally in such close proximity to a supermassive black hole. The research team concluded that S301 likely belonged to a binary system that was torn apart by the black hole's gravity, trapping S301 while ejecting its companion outward.
Because the star appears two billion times fainter than Betelgeuse in the night sky, researchers relied on the GRAVITY+ instrument to combine light from four eight-meter telescopes. This setup yielded a virtual telescope with a spatial resolution 15 times greater than any single instrument could achieve independently.
Implications for Measuring Black Hole Spin
Astrophysicists plan to track S301 through its next closest approach to Sagittarius A*, which is scheduled for 2031. Observing multiple complete orbits will allow scientists to map its trajectory with extreme precision, potentially yielding the first direct measurement of a supermassive black hole's rotation axis. According to general relativity, a rotating black hole drags space-time along with it, altering the orbits of nearby stars.
Research teams at the Paris Observatory and participating international institutions will continue monitoring positional metrics ahead of upcoming orbital milestones.
Why is the newly discovered star S301 important for physics research?
S301 is important because its exceptionally close and fast orbit around Sagittarius A* allows astronomers to test Einstein's theory of space-time and potentially measure the rotation of the Milky Way's central black hole within a decade.
The discovery was formally announced by international researchers on August 21, 2026.
The star will complete its next close approach to the black hole in 2031.