London, Oct. 31: A newly-identified star in the southern Milky Way that may be the oldest ever found will provide clues to what the universe was made of shortly after the Big Bang.
The star is approximately 36,000 light years from the earth and about 10,000 times fainter than the faintest stars that can be seen with the unaided eye.
Called HE 0107-5240, the stellar relic of an ancient cosmos is described today by a team from Germany, Sweden, Australia, Brazil and America in the journal, Nature.
Located in the constellation Phoenix in the southern hemisphere, the star is between 14 billion and 15 billion years old. “That’s more than three times the age of our sun, which is a mere 4.5 billion years old,” said Prof Timothy Beers of Michigan State University.
“This is the closest astronomers have come to having direct knowledge of the elemental composition of the universe shortly after the Big Bang. Chemically, this is the most primitive object that’s ever been found.”
The clue to its age is that the star has an extremely low metal content, consisting virtually of hydrogen and helium, the elements created in the Big Bang.
Beers said the star contains about 20 times less metal than the previous record for this kind of star. It proves that, contrary to most theories, comparatively light stars such as HE 0107-5240 may form in environments nearly devoid of heavier elements.
“This also tells us that stars were able to form right from the beginning,” he said. “There wasn’t a significant delay. It tells us where we started from and sets the chemical recipe of the early universe.”
This star was found in the halo of our Milky Way Galaxy, a low-density region of the galaxy where the stars are considerably older than those found in the disk, or the plane, of the galaxy, where the sun is located.
It was found during a decade-long survey of the southern sky, with follow-up observations at the ESO Paranal Observatory in Chile.
The Milky Way was formed when the universe was young from a gigantic cloud of gas, believed to be composed almost exclusively of hydrogen and helium atoms produced during the Big Bang.
However, once the first stars formed, heavier elements were built up by nuclear processes in their interiors.
As time passed, many of the stars of this and following stellar generations returned the processed matter to their surroundings at the ends of their lives, either during violent supernova explosions or strong “stellar winds”.
In this way, the interstellar gas in the Milky Way has been continuously enriched with heavier elements.
Stars of later generations such as our Sun now contain those elements produced by their ancestors.