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Star S301’s orbit could reveal Sagittarius A* spin by 2031

8/22/2026

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Summary

Story summary

German astronomers discovered star S301 orbiting the Mil Way’s central black hole Sagittarius A*.
S301 travels at about 25,000 km per second, over 8 % of light speed.
Its 8.7-year highly eccentric orbit brings it within 12 AU of Sagittarius A*.
Researchers say the star likely originated from a binary torn apart by the black hole.
The star’s motion could enable direct measurement of Sagittarius A*’s spin by 2031.

History

Historical Context

In 1995 two teams began tracking star S2 around Sagittarius A*, proving the Milky Way’s central black hole. Decades of ESO-VLT observations refined its 16-year orbit and relativistic effects. Now the Max Planck Institute for Astronomy reports star S301 racing at 25,000 km s?¹ (?8 % c) on an 8.7-year, 12-AU orbit, enabling spin measurements of Sagittarius A* by 2031.

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Story summary

German astronomers discovered star S301 orbiting the Mil Way’s central black hole Sagittarius A*.
S301 travels at about 25,000 km per second, over 8 % of light speed.
Its 8.7-year highly eccentric orbit brings it within 12 AU of Sagittarius A*.
Researchers say the star likely originated from a binary torn apart by the black hole.
The star’s motion could enable direct measurement of Sagittarius A*’s spin by 2031.

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