30 July 2022
The overwhelming majority of stars have planets. We all know that from observations of exoplanetary techniques. We additionally know some stars don’t have planets, and maybe they by no means had planets. This raises an fascinating query. Suppose we see an previous star that has no planets. How do we all know if ever did? Perhaps the star misplaced its planets throughout an in depth method by one other star, or possibly the planets spiraled inward and had been consumed like Chronos consuming his kids. How might we presumably inform? A latest research on the arXiv solutions half that query.
All of it comes all the way down to an odd little component often known as lithium.
Lithium is the third component on the periodic desk. Though a lot of the atoms shaped through the huge bang had been hydrogen and helium, hint quantities of lithium had been shaped from the massive bang. About one atom in ten billion so the present mannequin goes. However it seems there may be much less lithium within the universe than you’d anticipate. That’s as a result of whereas different components equivalent to carbon, oxygen, and iron are created within the hearts of huge stars, lithium is destroyed. It’s an impact often known as lithium burning, and it means older stars usually don’t have a lot lithium current of their environment.
Astronomers use this impact to differentiate between high-mass brown dwarfs and low-mass stars. If there may be loads of lithium current within the environment, then fusion isn’t occurring, and it’s a brown dwarf. Not a lot lithium and you’ve got a star. However some stars have atmospheric lithium. They’re clearly massive sufficient and scorching sufficient to bear fusion, they usually haven’t burned lithium out of their environment. So what provides?
The frequent speculation has been that these uncommon stars should bear some uncommon inside mixing that by some means prevents lithium from being cycled into the star’s inside the place it may be consumed. This newest research proposes another. Maybe these stars occurred to devour their younger planets as a substitute.
Since planets don’t burn lithium when a planet is eaten by a star its lithium is added into the star’s combine. The workforce simulated how that added lithium would behave in a star’s inside, and the way lengthy it will take to fade from the star’s higher layers. They discovered that smaller crimson dwarf stars are pretty efficient in burning the brand new lithium. As a result of a small star has massive convection zones that blend its inside rather well, inside a couple of hundred million years the brand new lithium is depleted. However for bigger, extra Solar-like stars, lithium can grasp round for billions of years. Lengthy after a planet is consumed, its lithium remains to be current within the stellar environment.
So if we see an previous Solar-like star with lithium in its environment, it’s fairly potential it as soon as had planets. Stellar lithium appears to be signal of a sated star after a planetary meal.
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