( N.R.Fuller | National Science Foundation )
Astronomers report spotting the traces of the earliest light in the universe believed to come from the first stars that formed around 180 million years after the Big Bang.
The universe used to be dark and filled with hydrogen but some of the gas later formed into stars that illuminated the cosmos, affecting the hydrogen gas and producing a signal.
Fingerprints Of The First Stars
Alan Rogers, from MIT's Haystack Observatory, and colleagues said that they found the apparent fingerprint of these first stars of the universe.
"This is the first real signal that stars are starting to form, and starting to affect the medium around them," said Alan Rogers, from MIT's Haystack Observatory. "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."
Dark Matter
The discovery also offers clues about the nature of dark matter. Scientists said that the signal was twice as intense as predicted.
One theory proposed that the hydrogen gas in the early universe was significantly colder than previously thought. A possible explanation for this is that the hydrogen atoms in the early cosmos had direct interaction with dark matter.
Ordinary matter makes up only about 15 percent of the universe. Dark matter is thought to make up a larger portion of matter in the universe but it was never directly observed. Scientists know it exists because it has been detected through its gravitational interactions with visible matter in the cosmos.
Ordinary matter has been heating up since the Big Bang but the dark matter has been cooling down. If the particles of normal and dark matters collide because of some non-gravitational force, astronomers said there would be heat transfer from warmer to a cooler object.
Hydrogen Gas Could Be Cooled By Dark Matter
Tel Aviv University astronomer Rennan Barkana, who studies early stars, suggested that the hydrogen gas could be cooled by interaction with dark matter particles.
"The only way to cool [the gas] is for something else, which is even colder, to take heat away," said Barkana. "The only candidate constituent of the universe that could have been even colder than the gas is the dark matter."
Cooling from dark matter in the current universe would be drowned out by the heating effects of the likes of stars and black holes, so the cosmic dawn offers a unique opportunity to study dark matter's heating effects that cannot be observed today.
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