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From our point of view, stars last a very long time, generally measured in millions of years. As with anything, however, they go through cycles of creation and destruction.
In the time just after the Big Bang, it is theorized that the stars that formed were made entirely of hydrogen and helium and had no heavier elements in them, or at least very little. These earliest stars are called population III stars.
As those stars burned out formed metals that were pushed out into the universe, future generations of stars were not as ‘clean’ and contained those metals. NASA explains that these earliest stars were bright and hot:
“Massive Population III stars could have been as hot as 100,000 kelvins – more than 90,000 degrees hotter than the Sun. The hotter any object is, the more electromagnetic radiation (light) it gives off, and the higher energy the radiation is. Population III stars would have been much brighter than the Sun, giving off mostly high-energy ultraviolet rather than visible light.”
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These early stars are almost certainly all gone by now since they formed so long ago. According to a new paper that is posted in preprint on arXiv, however, it is possible that there are still some of the second generation of stars burning bright, and one may have been found. The authors explain:
“The first stars formed out of pristine gas, causing them to be so massive that none are expected to have survived until today. If their direct descendants were sufficiently lowmass stars, they could exist today and would be recognizable by having the lowest metallicity (abundance of elements heavier than helium).”
Astronomers have found many pristine stars with low metallicity over the years, with many more being found using the James Webb Space Telescope. One newly analyzed star, however, seems to have far less metal than any others. In the paper, they write:
“We find that J0715−7334 is the most metal-poor star known, with Z < 7.8 × 10−7. This is about two times more metal-poor than the previous record holder, J1029+1729.”
This star stands out even more in the fact that it has such little carbon. Most of the low-metallicity stars have lots of carbon in them, but not this one.
“The detailed chemical abundances of the most metal-poor stars can be linked back to the properties of metal-free Population III stars through supernova nucleosynthesis models. J0715−7334 is an especially clean probe of Population III, as its distant halo orbit completely precludes significant surface contamination from the interstellar medium, and its large convective envelope removes any diffusive settling effects. Overall, this star is best explained by a 30 [solar mass] progenitor star and a high explosion energy around 5 × 1051 erg.”
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While it cannot be confirmed that this is indeed a second-generation star, it is almost certain that it is a very old one, or at the very least, that it was formed from gas that was once in a Population III star and hasn’t passed through other stars in the years since.
This type of discovery helps astronomers learn more about the earliest times of the Universe.
If you thought that was interesting, you might like to read about a quantum computer simulation that has “reversed time” and physics may never be the same.