Here in the Sun there are only about 2% of such elements. Among them, the most abundant are carbon and oxygen – elements that form when helium nuclei fuse.
Over time, such elements become more abundant in the Universe and in each star, while hydrogen decreases. It is believed that lithium should also decrease: although it is rarely involved in thermonuclear reactions, they should always destroy lithium, not increase it.
So it is likely that old stars should have less lithium than young ones. But there are also anomalies: it was recently discovered that one elderly star contains lithium more than in any other.
Astronomers chose the star J0524-0336 to study because it is quite old – and has already passed the giant stage.
After measuring its spectrum, scientists discovered that there are not many metals in general, about 270 times less than in the Sun. However, there is about 100 thousand times more lithium in it than in our star.
How the star could have acquired such a chemical composition is unclear, but the authors of the study present two hypotheses.
The first is that the star acquired lithium from external sources, such as a recently eaten planet. There are many known cases of an aging star swallowing its planets. If this happened relatively recently, such as in the last few centuries, the remnants of the planet have not yet had time to sink deep into the star, so they can be seen in the star’s spectrum.
Another hypothesis is that the star is going through a very short evolutionary stage called a lithium flash. For now, this stage is purely theoretical – although evolutionary models predict it should happen, no stars have yet found signs of it.
Longer observations will help distinguish which hypothesis is correct: if the star received lithium from the outside, its abundance should change noticeably in just a few years. Also, it is likely that the star is spewing material in this case. The current data show evidence of such spitting, but are not statistically significant.
Research results on arXiv.
2024-08-27 09:34:35