The asteroid remains of a white dwarf star could help astronomers find “missing” lithium

Crushed asteroids found in the atmosphere of a dead white dwarf star could help astronomers find and measure the missing lithium in the universe.

Measurements of lithium in stars like our own Sun have never added to the amount that scientists predict should exist, suggesting that there is much more than we can find.

The Big Bang, the main explanation for how the universe began 13.8 billion years ago, produced three elements: hydrogen, helium, and lithium.

Of the three elements, lithium presents the greatest mystery. But the new study by astronomers at the University of North Carolina provides clues to track its evolution.

Finding traces of the element in the rocky remains of an asteroid in the atmosphere of a nine-billion-year-old white dwarf could help scientists estimate the total amount of lithium in the universe, as it suggests that it can disperse into rocky bodies.

This is the first time the hard-to-find element has been identified in the burned remains of a dead star, according to researchers at the University of North Carolina.

Despite its many uses on Earth to power electronics and stabilize moods, scientists have been surprised by what has happened to the expected Big Bang lithium, a discrepancy known as the “cosmological problem of lithium.” .

No one knows exactly how much lithium there is in the universe, but these new findings mean that white dwarf stars could be used to estimate the total amount.

The discovery was made possible by the use of a unique spectrograph mounted on the Southern Astrophysical Research telescope.

The study’s author, astrophysicist J. Christopher Clemens, led the design of the Goldman Spectrograph that measures the amount of light a white dwarf emits.

White dwarfs are the nuclei that remain when stars die and may be surrounded by rocky worlds. Our Sun will become a white dwarf when it dies.

The high surface gravities of these stars should cause elements heavier than hydrogen and helium to sink rapidly below the surface.

However, some “contaminated” white dwarf stars show evidence of heavier elements on their surfaces, which are believed to be due to the recent accretion of rocky bodies.

In the study, researchers describe the detection of crushed remnants of large asteroid-like objects in the atmosphere of two very old white dwarfs.

The planets of these dead stars formed nine billion years ago: our Sun and the planets formed only 4.6 billion years ago.

The team measured the chemical composition of asteroids and, for the first time, identified and measured both lithium and potassium from an extrasolar rock body.

The theory predicts that lithium formed mainly in the first five minutes after the Big Bang. Its later history is different from other elements and is more uncertain because lithium is consumed by the nuclear reactions of stars.

Finding it in white dwarf stars provides a record of the original rocky bodies that formed nine billion years ago (and therefore the abundance of galactic lithium at the time they formed) during the early billion years of the universe.

The authors note that accumulated bodies such as those that contaminated this star “represent an alternative to old stars to obtain information about the original.” [lithium] abundance, the earliest epochs of chemical enrichment of our galaxy, and the properties of ancient exoplanets.

“Our measurement of the lithium of a rocky body in another solar system lays the groundwork for a more reliable method of tracking the amount of lithium in our galaxy over time,” Clemens said.

“Finally, with enough of these white dwarfs that had asteroids falling on them, we can test the prediction of the amount of lithium formed in the Big Bang.

The findings have been published in the journal Science.