The Archaeology of the Stars

A drawing of the Giant Magellan Telescope, which will be set up in the Atacama Desert in Chile and allow an even deeper look into the early universe. Todd Mason/Giant Magellan Telescope Organization

Four years ago, Anna Frebel, a young astronomer at the Massachusetts Institute of Technology, found an ancient star in a neighboring galaxy whose chemical composition proved nearly identical to some unusual stars on the outskirts of our own galaxy, which are older than the Milky Way itself. It was a striking discovery, suggesting that the relatively young Milky Way is growing by conquest — “cannibalizing” nearby older dwarf galaxies. And it underscored the importance of a new way of learning how the universe evolved from the Big Bang to the modern cosmos.

Traditionally, astronomers study the early universe by looking back in time — peering deeper and deeper into space for vestiges of light from billions of years ago. But in the last decade, Dr. Frebel and others have used powerful telescopes and high-resolution spectroscopes to study the chemical composition of very old stars closer to home, in the Milky Way’s halo, producing a wealth of information about the creation of elements and the formation of the first stars and galaxies.

These astronomers are like Egyptologists combing the desert for relics of bygone civilizations, and call themselves stellar archaeologists. Their work relies on the fact that the rare, primordial stars they are looking for have very few atoms heavier than hydrogen and helium, the gases from which they came together. By contrast, our sun and other relatively young stars are rich in other elements, which astronomers collectively refer to as metals.

Astronomers believe that some of the old stars formed from the chemically enriched dust left over from the explosive deaths of the very first generation of stars, and their atmospheres contain important information about their forebears, like DNA passed from parent to offspring.

The hunt for these scarce antiquities goes back to the early 1950s, when scientists recognized that not all stars have the same metal-rich chemical composition as the sun. “At the time, they didn’t know what to do with the metal-poor stars,” Dr. Frebel, 33, said.

But astronomers have since established what she called “a framework for the chemical evolution of the universe.”

Read the whole article here The Archaeology of the Stars

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