Red giants are evolved stars that have converted all of the hydrogen in their cores to helium through nuclear fusion and are now burning hydrogen in their shells. These stars begin to burn the helium in their cores as they near the conclusion of their lifetimes.
In our Milky Way Galaxy, there are millions of red giants. In around 4 billion years, our Sun will become one of these extremely luminous stars.
Astronomers have anticipated the appearance of thinner red giants for a long time.
Yaguang Li and colleagues from the University of Sydney can now prove their existence after discovering a sprinkling of them.
“It’s like tracking down Waldo. In a sea of typical red giants, we were extraordinarily fortunate to uncover 39 thinner red giants. The leaner red giants are either smaller or less large than regular red giants, according to Li.
“How and why did they lose weight?” The majority of stars in the sky are in binary systems, which are made up of two stars that are gravitationally linked to one another.”
“Some material can reach the gravitational sphere of its partner and be pulled away as stars in tight binaries expand, as stars do as they age.”
“We believe a partner might be present in the case of relatively small red giants.”
Li and co-authors used an asteroseismology approach to examine archival data from NASA’s Kepler mission, which included 7,538 helium-burning red giants.
Very low-mass red giants and underluminous (dimmer) red giants were discovered to be two sorts of peculiar stars.
The extremely low-mass stars have a mass of 0.5 to 0.7 solar masses, which is around half that of our Sun. The masses of the very low-mass stars would suggest that they were older than the age of the Universe if they hadn’t abruptly dropped weight, which is impossible.
“At first, we felt there was something wrong with the measurement when we got the masses of these stars. “However, it turned out there wasn’t,” Li explained.
The usual masses of the underluminous stars, on the other hand, range from 0.8 to 2 solar masses.
Dr. Simon Murphy, an astronomer at the University of Southern Queensland, remarked, “However, they are far less ‘giant’ than we predict.”
“They’ve shrunk slightly, and because they’re smaller, they’re also fainter, making them ‘underluminous’ in comparison to typical red giants.”
Only seven of these dimly lit stars were discovered, but the astronomers believe there are many more in the sample.
“The issue is that the majority of them are excellent at blending in. “Finding them was like a treasure hunt,” Dr. Murphy remarked.
Simple star evolution predictions could not account for these unique data values.
This prompted the researchers to believe that another process is at work, causing these stars to lose mass dramatically: mass theft by surrounding stars.