Fastest known star races around Milky Way’s black hole at 15,900 miles per second; how its orbit could reveal cosmic secrets

A star racing through the heart of the Milky Way at an astonishing speed could help astronomers uncover a hidden property of the galaxy’s central black hole. Named S301, the faint star reaches around 15,900 miles per second at its closest approach to Sagittarius A*, making it the fastest known star in the Milky Way by its measured orbital speed. But part of why this discovery is remarkable is the speed. Its unusually close orbit could give scientists a rare chance to see how a black hole’s spin affects the fabric of space and time.

What makes S301 the fastest known star?

Researchers identified S301 while studying stars near Sagittarius A*, the supermassive black hole at the centre of our galaxy. The black hole has a mass equivalent to about 4.3 million Suns and lies approximately 27,000 light-years from Earth.

According to research published in Nature on August 19, 2026, S301 reaches a peak speed of around 25,000 to 25,600 kilometres per second, equivalent to roughly 8.3% to 8.5% of the speed of light. The European Southern Observatory (ESO) described the discovery as a significant step towards investigating the properties of the black hole.


“What is special about this star is that it’s orbiting Sagittarius A* on a very tight orbit, taking just 8.7 years to complete it,” said Felix Mang, a researcher at the Max Planck Institute for Extraterrestrial Physics and an author of the study, in an ESO statement. Unlike a star moving through empty space, S301 is caught in an extremely elongated orbit around the black hole. Its gravitational pull accelerates the star as it approaches, allowing it to reach its extraordinary peak speed.

How close does S301 get to the black hole?

At its closest point, S301 comes within roughly 12 times the distance between Earth and the Sun from Sagittarius A*. That is comparable to the distance between the Sun and Saturn.

The star completes an orbit in 8.7 years, setting a record for the shortest known orbital period among stars observed around the Milky Way’s central black hole. Before its discovery, the record belonged to a star known as S55, which takes approximately 12 years to complete an orbit.

Tracking S301 was no easy task. It is extraordinarily faint, and astronomers had to combine observations from multiple years to establish its trajectory. The team used GRAVITY, an advanced instrument operating with the European Southern Observatory’s Very Large Telescope Interferometer in Chile. By analysing observations and revisiting older images, researchers assembled measurements tracing the star’s movement.

Could the star reveal how fast the black hole spins?

The most important implication of S301’s orbit is what it could teach scientists about Sagittarius A*. According to Einstein’s general theory of relativity, a rotating black hole can drag the surrounding fabric of space-time along with it. This phenomenon, known as frame dragging, influences the paths of nearby objects. Because S301 travels so close to Sagittarius A*, its orbit could provide a way to measure this effect and determine the black hole’s spin.

Reinhard Genzel, director at the Max Planck Institute for Extraterrestrial Physics and a Nobel Prize-winning physicist, said in the institute’s announcement that S301 probes the galactic centre much closer than the previously studied star S2. However, the measurement will require further observations. Researchers have yet to determine the star’s motion directly towards or away from Earth, leaving two possible orientations for its orbit.

What happens next?

Astronomers expect S301 to pass close to Sagittarius A again in 2031. Future observations, including those planned with the European Southern Observatory’s Extremely Large Telescope, may help to narrow down its orbit and boost the chances of measuring the black hole’s rotation.

Meanwhile S301 provides a unique natural laboratory to study gravity under extreme conditions. By following one faint star’s rapid journey around a black hole, scientists may gain new insight into how space-time behaves near some of the universe’s most powerful objects.