A team from the National Astronomical Observatories of China (NAOC) has identified 591 new hypervelocity stars. Led by Dr. Li Yinbi, their peer-reviewed study appears in the December 17 issue of The Astrophysical Journal Supplement Series.
While most stars in the Milky Way orbit the galactic center at steady speeds of 100 to 300 km/s, hypervelocity stars stand out by hurtling along at extraordinary velocities.
First theorized in the 1980s and confirmed in 2005, just 550 hypervelocity stars were known until now. This latest research from Chinese astronomers more than doubles that count with 591 newly detected examples. Notably, 43 of these could eventually break free from the Milky Way's gravity and venture into intergalactic space.
The discoveries stem from data collected by LAMOST, China's flagship optical telescope that observes up to 4,000 celestial objects per exposure. Operational since 2012, LAMOST maintains the world's largest spectroscopic database.
The team cross-referenced this with astrometric data from the European Space Agency's Gaia mission, launched in 2013 and now charting over 1.3 billion stars. "These two massive databases provide an unprecedented opportunity to uncover more hypervelocity stars," notes co-author Professor Luo Ali.
All identified stars reside in the Milky Way's stellar halo, largely built from merged satellite galaxies. These "sprinters" likely originated from such dwarf galaxies orbiting our own.
Months ago, astronomers revealed another hypervelocity star propelled by a close encounter with Sagittarius A*, the Milky Way's supermassive black hole. Roughly five million years ago, two stars approached it: one was consumed, but the survivor—S5-HVS1, 2.3 times the Sun's mass—gained a gravitational slingshot, reaching speeds over 6 million km/h. This eclipses the prior record holder, US 708, at 4.3 million km/h.
