On the other side of the Milky Way galaxy, astronomers have discovered an ancient star that contains evidence of the very first stars formed after the Big Bang.
The red giant star is 35,000 light-years from Earth, in the Milky Way’s halo. The unique thing about it is what it’s missing: iron.
Researchers used the SkyMapper Telescope at the Siding Spring Observatory in New South Wales, Australia, to find the star.
They performed spectroscopic analysis and learned that the star contained only one part iron per 50 billion. A study about the ultra-metal-poor star was published Thursday in the journal Monthly Notices of the Royal Astronomical Society: Letters.
“That’s like one drop of water in an Olympic swimming pool,” said study author Thomas Nordlander, postdoctoral researcher at the Australian National University and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions, known as ASTRO 3D. “This incredibly anaemic star, which likely formed just a few hundred million years after the Big Bang, has iron levels 1.5 million times lower than that of the Sun.”
The lack of iron is a record low level, which implies something intriguing about its history.
The first stars that appeared in the universe were probably made of the two most abundant elements, hydrogen and helium, with lithium traces. The elements were created during the Big Bang. Heavier elements would later be created by stars as they exploded, called supernovae.
But the first stars have yet to be discovered, so astronomers can only hypothesize their composition. They believe these stars would have been hundreds of times more massive than our sun, resulting in hypernovae even more energetic than supernovae.
This newly discovered star, named SMSS J160540.18-144323.1, isn’t one of the first stars. But the researchers who observed it think it’s one of the stars that formed after the first ones exploded.
The newfound star’s ancient ancestor that exploded was only 10 times more massive than the sun and experienced a more tame explosion. The heavy elements would have fallen back into the dense neutron star left behind by the supernova.
A small bit of iron escaped the gravitational pull of the neutron star to help form a new one: this newfound second-generation star born from one of the very first stars in existence.
The first stars may never be found, because the likelihood that any of them survived until now is small.
“The good news is that we can study the first stars through their children - the stars that came after them like the one we’ve discovered,” said study author Martin Asplund, chief investigator of ASTRO 3D.