Fastest S-Star Discovered Near Milky Way's Supermassive Black Hole

• Astronomers have discovered S301, the fastest and closest S-star ever observed orbiting Sagittarius A* (Sgr A*), the Milky Way's supermassive black hole.
• The star completes an orbit in just 8.7 years and reaches a minimum distance of only 12 astronomical units (au) from the black hole.
• S301's extreme proximity allows researchers to study the Lense-Thirring effect, providing a direct method to measure the spin of the black hole and test Einstein's General Theory of Relativity.

Discovery and Characteristics

• S301 moves at approximately 25,000 kilometers per second.
• It was identified using the GRAVITY instrument on the Very Large Telescope (VLT) through a multi-year observational campaign (2017–2025) involving 19 total astrometric measurements.
• Due to being two billion times dimmer than Betelgeuse, the star remained difficult to detect until recent high-resolution modeling.

Scientific Significance

• The extreme environment near Sgr A* causes "orbital precession," where the closest point of the star’s orbit shifts over time due to the black hole dragging spacetime.
• Researchers anticipate that tracking S301 will enable a direct measurement of the black hole's spin within the next decade, a task that would have otherwise taken several more decades.

Origins of S301

• Scientists believe S301 formed elsewhere and migrated toward the galactic center.
• The prevailing theory is a "Hills disruption," where a binary star system was separated by the black hole's tidal forces, capturing S301 into its current orbit while ejecting its companion as a hyper-velocity star.