Thinner red giants lose mass under the influence of the gravity of the companion star

(ORDO NEWS) — There are millions of stars in our Galaxy that can grow up to 1 billion kilometers in size, but among them there is a small group of stars that have much smaller diameters.

In a new study, a team of astronomers from the University of Sydney, Australia, have discovered several new stars in this category.

“It’s like finding a needle in a haystack! We are incredibly lucky to have found approximately 40 “thinner” red giants among the huge number of known stars of this class. ‘thinner’ red giants are smaller or smaller than regular red giants,” said study author Yaguang Li of the University of Sydney.

Most of the stars in the Universe belong to the main sequence, and the processes of thermonuclear burning of hydrogen with the formation of helium take place in them.

As a result of this process, a large amount of energy is released. This energy tends to leave the star, but the gravitational action of the entire mass of the star’s material prevents this from happening. To ignite thermonuclear reactions, a star must have a mass of at least 0.08 solar masses.

When there is no hydrogen left in the core, fusion ceases, and the opposition to the gravitational pressure that compresses the core ceases, causing the temperature to rise. An increase in temperature initiates the combustion of a shell of hydrogen surrounding the inert core.

While this is happening, the helium core continues to contract and the temperature continues to rise, causing the star to expand and increase the amount of light it produces. This is how red giants are formed.

These newly discovered red giants are represented by two main classes: very low mass red giants and dim red giants. Astronomers from the University of Sydney analyzed data collected by NASA’s Kepler Space Telescope between 2009 and 2013.

These stars, which are very low-mass red giants, have masses between about 0.5 and 0.7 solar masses. To gain such a small mass naturally, they must be older than the age of the universe. Therefore, scientists tried to determine what is the reason for the “lack” of mass by these stars.

By studying the properties of the observed set of “thinner” red giants, Lee and his team determined that the reason for the “thinner” is a companion star that forms a binary system along with the red giant, the researchers show.

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