"It was previously believed that the cosmic heating occurred very early but we discovered a completely different picture," said Rennan Barkana, a professor at Tel Aviv University's school of physics and astronomy.

One of the exciting frontiers in astronomy is the era of the formation of the first stars.

"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," explained Barkana.

The findings result 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.

The new finding that cosmic heating occurred later than previously thought means that observers do not have to search as far and it would be easier to set the cosmic milestone.

In order to detect the expected radio waves from hydrogen in the early universe, several large international groups have built and begun operating new arrays of radio telescopes.

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, said the study published in the journal Nature.

(Agencies)

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