Astronomers have discovered what they think is one of the oldest stars in the Milky Way, dating back to just 300 million years after the Big Bang.
Called J0815+4729, the star is located 7,500 light-years from Earth towards the Lynx constellation. It’s thought to be about 0.7 times the mass of the Sun, but about 400 degrees hotter on its surface. It was found in the halo of the Milky Way, which is the region around the disk that contains most of its stars today. A study describing the star is available on arXiv.
Using the Gran Telescopio Canarias (GTC) in La Palma, Spain, the scientists were also able to deduce it has a millionth of the calcium and iron that’s inside the Sun, but about 15 percent of the carbon in our Sun. This makes it a metal-poor star, and points to its extremely old age of about 13.5 billion years.
“We know of only a few stars (which can be counted on the fingers of a hand) of this type in the halo, where the oldest and most metal-poor stars in our galaxy are found,” said David Aguado from the University of La Laguna (ULL) in Spain, the study’s lead author, in a statement.
“Theory predicts that these stars could form just after, and using material from, the first supernovae, whose progenitors were the first massive stars in the Galaxy, around 300 million years after the Big Bang,” added Jonay González Hernández, from the Canary Islands Institute of Astrophysics (IAC), a co-author on the study. “In spite of its age, and of its distance away from us, we can still observe it.”
Those oldest stars are known as Population III stars, hypothetical huge and extremely hot stars that are thought to have formed and gone supernova in the first few millions years of the universe. From these, stars like J0815+4729 may have been born.
It is not the only old star we’ve found in the Milky Way. We’ve found others before that seem to date to a similar time. But it highlights some of the secrets our galaxy is still hiding, and could help us work out how the first stars in the universe formed.
“Identifying and characterizing chemically these rare breed of stars will certainly shed light on the early chemical evolution of the galaxy and the nature of the first stars,” the team wrote in their paper.