A new star from an earlier simpler universe
Pristine by name and by nature, a star with almost no complex elements gives clues to the early universe Alan Duffy reports.
A star almost entirely devoid of elements more complex than helium could be an ancient relic from a younger, simpler universe.
A new systematic survey of stars around the Milky Way has delivered its first detection in a paper published in the journal Monthly Notices of the Royal Astronomical Society.
A team of researchers led by Else Starkenburg from the Leibniz Institute for Astrophysics Potsdam, in Germany, reveals an object that rivals the most pristine star ever found, and suggests a potential new way that such stars may have formed in the early universe.
Stars forge new elements in their core through nuclear fusion, which are then released into the wider universe to be reincorporated in future generations of stars. In time they may also form planets – and even Cosmos readers.
All elements heavier than the primordial hydrogen, helium and lithium -- which formed in the Big Bang – are termed “metals” by astronomers, and the increasing levels of these in the universe functions as a form of clock. Stars that appear to have formed from low metallicity clouds of gas are therefore more likely to be older than so-called metal-rich stars.
The star discovered by Starkenburg and her colleagues contains “less than one ten- thousandth of the metal content of the Sun”, and has been appropriately named Pristine 221.8781+9.7844. While many metal-poor stars exist, this class of ultra-metal-poor star has unique identifiers that set it apart.
“Whereas most metal-poor stars that exhibit such low levels of elements like iron and calcium also show a significant enhancement in carbon, this star does not,” explains Starkenburg.
“This makes it the second star of its kind ever discovered, and an important messenger from the early universe.”
This is the just first discovery of the new survey, also called Pristine, a dedicated search with filters tuned for maximum sensitivity to metal-poor atmospheres. It uses the Canada-France-Hawaii Telescope (CFHT) atop Mauna Kea in Hawaii.
The filters act to give narrow-band, or distinct colour, pictures of the sky, permitting the rapid identification of these unusual stars, effectively sifting the haystack of galactic stars to find these rare needles.