Astronomers have discovered one of the oldest stars in the known universe. They believe it is at least 13.2 billion years old and formed shortly after the Big Bang.
The astronomers announced their findings at the January 10th meeting of the American Astronomical Society in Long Beach, California¹. Howard Bond of Pennsylvania State University in University Park states that they believe that this star is the oldest known in the universe with a well determined age.
HD 140283 lies only 186 light years from our Solar System and has been studied for more than a century by astronomers. Researchers have long known that the star consists almost entirely of hydrogen and helium, indicating that it was formed in the early history of the universe. Successive generations of stars have had a chance to forge heavier elements.
In order to determine the star’s age, they scientists had to accurately determine its distance by using 11 sets of observations recorded between 2003 and 2011 by the Hubble Space Telescope. They were then able to calculate the star’s intrinsic luminosity with good precision. The team exploited the fact that HD 140283 has advanced to a phase where it’s exhausting the hydrogen at its stellar core. Stars at this phase will slowly start dimming in luminosity and that is a highly sensitive indicator of its age. The team calculated that the star is about 13.9 billion years old, +/- 700 million years. Within the error bracket, its age doesn’t conflict with the age of the universe that is 13.77 billion years.
The first stars coalesced from primordial gas, which didn’t contain any elements heavier than helium. Since HD 140283’s chemical composition contains a low but nonzero abundance of heavy elements, it must have formed after the first stellar generation.
- Bond, H. E., Nelan, E., VandenBerg, D. A., Schaefer, G. H. & Harmer, D. Abstr. 443.08 221st meeting of the American Astronomical Society, Long Beach, California (2013).