A relic from the early universe is cruising across the constellation Libra right now. It’s only about 200 light-years away, but it’s moving in a hurry — about 800,000 miles an hour. That’s far faster than most of the stars around us. So it’ll move out of Libra in a few thousand years — the blink of a cosmic eye.
The star is known as HD 140283. But it also has a nickname — the Methuselah Star. That’s because measurements of its age say it’s at least 13 and a half billion years old, and perhaps a good bit older. Since the universe itself is only about 13.8 billion years old, that makes the star one of the oldest around.
Astronomers have pieced together several bits of evidence to arrive at the star’s age. The key bit is its composition. HD 140283 has very low levels of heavy elements — anything other than hydrogen and helium, the simplest elements. Heavier elements were created in the hearts of earlier stars, then spewed into space when those stars died. The Sun has relatively large amounts of these elements, which tells us that it followed many generations of stars.
HD 140283 has less than half a percent as much iron as the Sun, with slightly higher levels of oxygen and a few other elements. Those abundances tell astronomers the star must have been born when the universe was in its infancy. That makes it one of the older stars around — and the oldest in our region of the galaxy.
Script by Damond Benningfield