Large star swallowing smaller star demonstrates Darwin instability
DOI: 10.1063/PT.5.029825
New Scientist : In January 2015 the Hubble Space Telescope captured images of a red nova, a star that suddenly brightened and then returned to normal, in the Andromeda galaxy. Brighter than novae but dimmer than supernovae, red novae occur when two gravitationally bound stars merge. As the stars come together, they expel gas that expands and cools, which makes the nova appear red. In the 2015 event, an extremely large yellow star ate a much smaller red one. The event was triggered by the Darwin instability, predicted by Charles Darwin’s son George almost 150 years ago, in which the spin of the larger star in a binary pair starts to slow over time and the smaller star eventually gets sucked in. Red novae are a relatively new class of variable star, with the first confirmed sighting in 2007.
