Astronomers at the University of Sydney have found a slimmer type of red giant star for the first time. These stars have undergone dramatic weight loss, possibly due to a greedy stellar companion. Published in Nature Astronomy, the discovery is an important step forward to understanding the life of stars in the Milky Way – our closest neighbours.
There are millions of ‘red giant’ stars found in our galaxy. These cool and luminous objects are what our Sun will become in four billion years. For some time, astronomers have predicted the existence of slimmer red giants. After finding a smattering of them, the University of Sydney team can finally confirm their existence.
“It’s like finding Wally,” said lead author, PhD candidate Mr Yaguang Li from the University of Sydney. “We were extremely lucky to find about 40 slimmer red giants, hidden in a sea of normal ones. The slimmer red giants are either smaller in size or less massive than normal red giants.”
How and why did they slim down? Most stars in the sky are in binary systems – two stars that are gravitationally bound to each other. When the stars in close binaries expand, as stars do as they age, some material can reach the gravitational sphere of their companion and be sucked away. “In the case of relatively tiny red giants, we think a companion could possibly be present,” Mr Li said.
