Our Sun which sits in the center of our Solar System is believed to be just over 4.6 billion years old. Although that seems unfathomably old to a human, for a star, it’s actually not all that impressive.
A new survey has found that one particular star here in our own Milky Way galaxy is much older than anyone thought. This incredibly old star is called 2MASS J18082002–5104378 B and astronomers now believe it to be a whopping 13.5 billion years old.
This discovery means more stars with very low mass and very low metal content are most likely out there—maybe even some of the universe’s very first stars.
Researchers were able to determine how old this Star is due to its incredibly low mass and metal content. Researchers think that newer stars tend to be very high in metallicity, but the Old Star’s metal content is extremely low. It’s also tiny, weighing in at only around 1/10th of the mass of our own Sun.
Andrew Casey, the co-author of the study, told ScienceAlert that they never discovered a star so low in mass and made of so few grams of metals. This finding tells them that the very first stars in the Universe didn’t have to all be massive stars that died long ago. These ancient stars could form from minimal amounts of material, meaning some of those relics from soon after the Big Bang could still exist today.
So, how come this incredibly old star is still alive? One reason is that its small size plays in its favour because huge stars tend to burn through their fuel much faster than the tiny ones. The Old Star only breaks the known mass limit to facilitate the burning of hydrogen, so it’s very slowly using up its fuel over billions of years.
The star is unusual because unlike other stars with very low metal content, it is part of the Milky Way’s “thin disk”—the part of the galaxy where our own sun lives.
Since this star is so old, researchers say it’s possible that our galactic neighbourhood is at least 3 billion years older than previously thought. The findings are published in The Astrophysical Journal.