Using a telescope in Australia, astronomers say they have glimpsed farther back in time than the Hubble Telescope to see what was happening when the first stars were forming.
It was morning in the universe and much colder than anyone had expected when light from the first stars began to tickle and excite their dark surroundings nearly 14 billion years ago.
Astronomers using a small radio telescope in Australia reported on Wednesday that they had discerned effects of that first starlight on the universe when it was only 180 million years old. The observations take astronomers farther back into the mists of time than even the Hubble Space Telescope can see and raised new questions about how well astronomers really know the early days of the cosmos, and about the nature of the mysterious so-called dark matter whose gravity sculpts the luminous galaxies.
“We have seen indirectly evidence of very early stars in the universe — stars that would have formed by the time the universe was only 180 million years old,” said Judd Bowman of Arizona State, leader of the experiment known as EDGES, for Experiment to Detect Global EoR, in an email. Dr. Bowman and his colleagues published their results in Nature Wednesday.
The presence of stars manifested itself as a telltale dip in the intensity of a bath of radio waves, so-called cosmic microwaves, leftover from the fires of creation itself. The dip meant that cosmic energy was being absorbed by primordial clouds of hydrogen gas that hung over the universe like a fog, but whose atoms had been thrown out of balance by the sudden presence of starlight.
The presence of the dip, at a characteristic wavelength of hydrogen, confirmed earlier predictions from models of how and when the stars were born. But the depth of the dip and the amount of the absorption was a surprise. It suggested that the gas inhabiting the cosmos was only half as hot as astronomers had calculated — only about 3 kelvin above absolute zero, or minus 454 Fahrenheit.
“This is difficult to explain based on our current knowledge and assumptions about astrophysical processes in the early universe,” Dr. Bowman said.
