The vast majority of stars have planets, scientists have confirmed this in observations of exoplanets.
There is not much lithium in the universe, it is easyis destroyed. And other elements - such as carbon, oxygen and iron - are created in the depths of large stars. This effect is known as lithium burning. It leads to the fact that in the atmosphere of old stars there is usually not much of this element.
Astronomers use this effect to distinguishhigh-mass brown dwarfs and low-mass stars. If there is a lot of lithium in the atmosphere, then thermonuclear fusion does not occur, and this is a brown dwarf. But some stars still found lithium in the atmosphere. They are clearly large enough and hot enough to undergo fusion, and they have not burned the element out of their atmosphere.
A common hypothesis was thatthese unusual stars must undergo an unusual internal mixing that somehow prevents lithium from cycling inside the star. In a new study, scientists have proposed an alternative. Perhaps these stars swallowed up their young planets instead.
Because planets don't burn lithium when a planeteats a star, its element is added to the mixture of the star. The team modeled how this added lithium would behave inside the star and how long it would take to disappear from the star's upper layers. They found that smaller red dwarfs burn new lithium quite efficiently. Since a small star has large convection zones, new lithium is depleted over several hundred million years. But for larger, more Sun-like stars, it can exist for billions of years. Long after a planet is consumed, its lithium is still present in the stellar atmosphere.
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