Red Giant “Star Songs” Reveal Their Chaotic Pasts
Milky Way map indicating locations of Gaia BH1 and BH2The location of the first two black holes discovered by ESA’s Gaia mission in the Milky Way. Gaia Black Hole 1 is located just 1560 light-years away from us in the direction of the constellation Ophiuchus and Gaia Black Hole 2 is 3800 light-years away in the constellation Centaurus. Credit: ESA / Gaia / DPAC; CC BY-SA 3.0 IGO
Astronomers have recently tuned in to the “celestial songs,” or oscillations, of two red giants to reveal their remarkable secrets: One is guilty of consuming its companion in a case of stellar cannibalism, while the other may be almost as old as the universe.
The potentially cannibalistic red giant, called BH2*, orbits a dormant black hole, forming a binary system called Gaia BH2. It is a dying star similar to the Sun in mass, though it has ballooned to many times its size in its death throes. Its unexpected age and rotational rate suggest a turbulent past in which it engulfed its companion star — an astronomical twist worthy of Greek classics.
The second red giant, BH3*, also orbits a dormant black hole in a binary system called Gaia BH3. It is an ancient star that’s defying current cosmological models by not displaying the substantial oscillations, or variabilities in its brightness, that astronomers predicted.
These black-hole-anchored binary systems are notable for being some of the closest black hole systems to Earth. Gaia BH2 is located 3,800 light-years away in the constellation Centaurus, while Gaia BH3 is only 1,900 light-years away in the constellation Aquila.
(Source: skyandtelescope.org)
