US scientists detect oldest stars for first time

SAN FRANCISCO

Scientists have detected signals from the earliest stars in the universe for the first time ever, researchers announced Wednesday.

The astronomers say the signals originated from stars created 13.6 billion years ago, or within 180 million years of the Big Bang -- the enormous cosmic explosion that scientists believe gave birth to the universe.

The revelations provide evidence that the infant universe was full of hydrogen gas and extremely cold. The researchers believe the ancient universe was a chilly -270 degrees Celsius (-454 degrees Fahrenheit), much colder than earlier estimates.

The researchers worked out of Arizona State University, the University of Colorado at Boulder, and the Massachusetts Institute of Technology. The group’s findings were published in the journal Nature.

The first stars were large, blue, and short-lived, making them impossible to see with telescopes. In order to discover the stars, the astronomers used an antenna about the size of a refrigerator to detect minute changes in electromagnetic radiation far out in space.

"Finding this minuscule signal has opened a new window on the early universe," said lead investigator Judd Bowman of ASU in a statement.

"Telescopes cannot see far enough to directly image such ancient stars, but we've seen when they turned on in radio waves arriving from space."

As part of the discovery, the researchers also found the earliest hints of the element hydrogen in the universe. Hydrogen is the gas that fuels most stars.

"This is the first real signal that stars are starting to form, and starting to affect the medium around them," said study author Alan Rogers of MIT in a statement.

"What's happening in this period is that some of the radiation from the very first stars is starting to allow hydrogen to be seen. It's causing hydrogen to start absorbing the background radiation, so you start seeing it in silhouette, at particular radio frequencies."

The study’s finding that the universe was likely much colder than earlier thought will be a subject of study for some time to come, the researchers said, because it contradicts current models of how the universe developed. The scientists said it could provide clues about dark matter, a theoretical form of matter that is distinct from all other matter in the universe.