Astronomers Find the Fastest Star in Milky Way
News Desk
Astronomers have identified what is believed to be the fastest-known star in the Milky Way, offering scientists a rare opportunity to study the extreme environment surrounding the supermassive black hole at the centre of our galaxy.
Named S301, the star is travelling around Sagittarius A at speeds of up to 25,000 kilometres per second, equivalent to about 8.5 percent of the speed of light.
What makes the discovery particularly significant is the star’s remarkably close orbit. S301 completes a journey around the black hole in just 8.7 years and comes within roughly 136 Schwarzschild radii of Sagittarius A. That puts it about 10 times closer to the black hole than S2, the previous record-holding star and one of the best-studied stars near the galactic centre.
The extreme orbit could turn S301 into a powerful tool for testing some of the most challenging predictions of Einstein’s theory of relativity.
Researchers used the European Southern Observatory’s Very Large Telescope Interferometer in Chile’s Atacama Desert to study the star. The facility combines the light collected by four eight-metre telescopes, allowing astronomers to observe the crowded region around the black hole with exceptional precision.
One of the key phenomena scientists hope to investigate is Lense-Thirring precession. This effect occurs when a rotating black hole drags the surrounding spacetime along with its rotation, potentially altering the orientation of objects orbiting it.
S301’s unusually close passage to Sagittarius A could make these effects easier to detect than in the orbits of previously known stars.
The star’s origins are another part of the mystery. Scientists believe S301 may not have formed near the galactic centre. Instead, it could have been brought into the black hole’s vicinity through the Hills mechanism, in which the immense gravitational pull of a supermassive black hole tears apart a binary star system and sends one of the stars away while capturing the other.
Its highly elongated orbit, with an eccentricity of about 0.98, supports this possible explanation.
Beyond setting a new speed record, S301 could help answer a much bigger question: how rapidly Sagittarius A is spinning.
If astronomers can determine the black hole’s spin by precisely tracking changes in S301’s orbit, the discovery could provide the first measurement of the spin of a quiescent galaxy’s central black hole.
The finding therefore gives researchers more than a record-breaking stellar speed. It provides a new natural laboratory for examining black-hole physics, spacetime and the violent gravitational forces operating at the heart of the Milky Way.
