Key Takeaways
- Astronomers have discovered S301, the fastest known star in the Milky Way, orbiting Sagittarius A* at 15,500 mph.
- S301 completes its orbit in 8.7 years, coming within 12 times the distance from Earth to the sun.
- This discovery could allow direct measurements of the spin of Sagittarius A*, providing key insights into black hole physics.
Fastest Star Discovered Near Supermassive Black Hole
Astronomers have confirmed the discovery of S301, the fastest star in the Milky Way, which races around Sagittarius A*, the galaxy’s supermassive black hole. This faint star reaches speeds of approximately 15,500 miles per second, or over 8% of the speed of light.
Study author Felix Mang, a Ph.D. student at the Max Planck Institute for Extraterrestrial Physics, noted that S301’s notable proximity to the black hole—which is only 12 times the distance from Earth to the sun—allows it to complete an orbit in just 8.7 years. This unique trajectory offers astronomers a new method to study the 4.3-million-solar-mass black hole.
Critical to this research is the prediction of general relativity regarding a rotating black hole’s ability to drag spacetime with it, a phenomenon known as frame dragging or Lense-Thirring precession. As S301 orbits close to Sagittarius A*, changes in its path could become measurable within the next decade. Co-author Stefan Gillessen emphasized that these measurements will enable researchers to gain direct insights into the spin of a massive black hole, a significant test of Einstein’s theory.
The researchers tracked S301 using the GRAVITY instrument at the European Southern Observatory’s Very Large Telescope Interferometer in Chile. The team’s observations date back to 2021 and 2017, showcasing the star’s elongated orbit and indicating that it may have originated from a binary system. This system likely got too close to Sagittarius A*, resulting in S301 being captured while the other star was expelled at high speed.
Future observations of S301 are planned with GRAVITY+ and the Extremely Large Telescope. The star’s next close pass is anticipated in 2031, which will help scientists observe two complete orbits and potentially measure the spin of Sagittarius A* for the first time. The findings were published in the journal Nature on August 19.
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