Cosmic Dawn

Looking in the universe is like looking through time. And this has led the astronomers from Arizona State University and MIT to find out about the time when the first stars light up-which was just 180 million years after the Big Bang. Astronomers call it the “Cosmic Dawn”.

In early years, universe was in total darkness. This phase is generally referred to as the “Cosmic Dark Ages”. It was a phase when universe was a very cold and a very dark place. It consisted of only hydrogen gas, which made up the majority of the interstellar medium. Yet it was indistinguishable from all the cosmic radiation that was left behind by the Big Bang.

But time passed and the matter started clustering together; it grew larger and exerted enough pressure to start nuclear fusion.  And this is how the first stars in our universe flickered!  The UV radiation emitted by these stars reacted with the hydrogen in the surrounding and it’s this reaction which was observed now!

Different phases from Big Bang till Now

"This is the first real signal that stars are starting to form, and starting to affect the medium around them," says Alan Rogers, co-author of the new study. "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 team traced this signal back to 13.6 billion years- which is approximately 180 million years, just after the Big Bang. Due to this, it is the most ancient signal to be ever detected from the universe.

DETECTION OF THESE ANCIENT SIGNALS:

This detection was done by using the Experiment to Detect Global Epoch-of-Reionization Signature (EDGES), which is a small radio antenna that’s of size a tabletop.  To make sure that this equipment detected such sensitive signal, it was located in the remote region of Australia, hundreds of kilometers away from any human radio interferences.

Experiment to Detect Global Epoch-of-Reionization Signature (EDGES)

Generally, neutral hydrogen emits radiation at a frequency of 1,420 MHz. But due to the Doppler’s effect and the continuous expansion of the universe, this frequency was reduced.  It is estimated that by the time it reaches Earth, it will be up to 100 MHz. So EDGES was set to receive frequencies between 100 to 200 MHz.  But this didn’t work. As they assumed that 100 MHz would be when hydrogen would hotter than everything around it.  So they adjusted the calculations and set the frequency between 50-100 MHz.

This correction also draws certain conclusions. The calculations suggest that the primordial universe was twice as cold as it was thought to be- approximately -454 degree F. Scientists are still not sure about this considerable chill. But soon, they will find out. Some say that it could be related to Dark matter. The faint imprints left by these stars have some new and unexpected evidences about the Dark matter. This could be the second major breakthrough in this study of the Cosmic Dawn.