Universe Warmed Up Later Than Thought; Finding Could Mean We Don't Have To Reach As Far To See Earliest Stars
New research suggests the black holes that formed the universe's first stars may have heated up space gas later than we thought.
Researchers can look back on these black holes by pinpointing "signature radio waves" imposed by the objects, an American Friends of Tel Aviv University news release reported.
"One of the exciting frontiers in astronomy is the era of the formation of the first stars," Professor Rennan Barkana of TAU's School of Physics and Astronomy, said in the news release. "Since the universe was filled with hydrogen atoms at that time, the most promising method for observing the epoch of the first stars is by measuring the emission of hydrogen using radio waves."
Light from distant objects in outer space take a long time to reach Earth, allowing researchers to directly observe how things were in the distant past; If scientists "look out far enough" they could see what the first stars looked like during the universe's earliest days.
The fact that the universe heated later than we thought means scientists don't have as far to look.
Cosmic heating could allow researchers to gain insight into ancient black holes that were most likely fueled by a system called "black-hole binaries." These are two-star systems in which one star has died in a supernova explosion leaving a black hole-remnant behind. Gas from the surviving star is pulled into the black hole causing it to give off high-energy X-ray radiation. The radiation traveled long distances and reheated cosmic gas.
"It was previously believed that the heating occurred very early," Barkana said. "But we discovered that this standard picture delicately depends on the precise energy with which the X-rays come out. Taking into account up-to-date observations of nearby black-hole binaries changes the expectations for the history of cosmic heating. It results in a new prediction of an early time (when the universe was only 400 million years old) at which the sky was uniformly filled with radio waves emitted by the hydrogen gas."
New arrays of radio telescopes will be used to detect these waves.
"These arrays were designed under the assumption that cosmic heating occurred too early to see, so instead the arrays can only search for a later cosmic event, in which radiation from stars broke up the hydrogen atoms out in the space in-between galaxies. The new discovery overturns the common view and implies that these radio telescopes may also detect the tell-tale signs of cosmic heating by the earliest black holes," the news release reported.