Scientists have discovered two new types of red giants. Some of them have tiny mass, and others are too dim compared to ordinary ones. Perhaps the reason is an invisible companion, forcing them to “lose weight”.
“Slim” Red Giants
Astronomers from the University of Sydney reported the discovery of two anomalous types of red giants. This type of luminary, which is one of the last stages of the evolution of stars similar to our Sun, is quite common in the Galaxy. And they have certain ranges of masses and luminosities.
However, an article published in Nature Astronomy provides examples of red giants with non-standard parameters. Some of them have a mass of 0.5 to 0.7 solar masses. Until now, scientists have not seen a single red giant with a mass less than 0.8 solar. Stars smaller than this boundary can turn into huge red stars. But they evolve too slowly to have time to reach this stage during the existence of the Universe.
In addition, several red giants with abnormally low luminosity have been found. Scientists suspect that even here, there was a loss of mass. In total, they found 7 similar objects. But they merge very much with the background, so astronomers suspect that there may be much more of them.
Companions devouring the mass
Red giants are cold stars with high luminosity. This is exactly what our Sun will become in a few billion years. Radiation inflates its outer layers beyond the orbit of Venus. However, the Sun is a single star. Most of the luminaries in the Galaxy are part of multiple star systems.
And this invisible companion from Earth can explain the lack of mass in all the cases noted. It can be not only a black hole or a neutron star, but also a white dwarf or even a star like the Sun. After all, at the distances at which we see anomalous red giants, it is impossible to notice even such large stars as our luminary.
According to Рhys.org