Before the beginning of space and time, there was nothing. Then, 13.8 billion years ago, a big bang happened and spacetime came into existence. However, after an initial flash, the universe went into cosmic darkness. According to a study published on June 14, light returned to the cosmos after 250 to 350 million years of the Big Bang. This was the age of cosmic dawn when the first stars formed introducing starlight to the dark universe. Interestingly, we can still see the initial starlight from the cosmic dawn that has been travelling to us for billions of years, if we look far enough. How is that possible?
Astronomy is history and telescope in a time machine -this is a sentence an astronomer can often be heard saying. So, when we look at faraway objects in space using our powerful telescopes, we are actually looking at the light that was released way before it reaches our telescope, thanks to the limited speed of light - 3,00,000 kilometres per second. Using this special tool, we can look at father objects to look more back in time. For example, if we want to look a million year back in time, we need to look at the light coming from an object that is a million light-years away from us. The only challenge is that the light coming from farther places gets fainter.
This is the reason why the images we have of the most distant first galaxies, seen through the Hubble Space Telescope and the Spitzer Space Telescope, are faint and just a few pixels on the scientists’ computer screens. Now, scientists expect that a new and more powerful NASA’s James Webb Space Telescope that will launch this year will let us have a clearer view of the first galaxies and take us farther back in time. The telescope will help scientists discover and know more about the cosmic dawn, which has been Richard Ellis’s life’s work.
“Because we are ourselves the produce of stellar evolution, we are looking back at our own origin," Ellis told BBC News.
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