Finding first light from the cosmic dark ages with the SKA
Two major projects the Square Kilometre Array (SKA) will be working on is first light, how light arose in the Universe. A quick recap on the SKA: It’s a radio telescope 10,000 times more powerful than current models. Made up of dishes linked to a data processing unit, the instrument will stretch at least 3,000 kilometres across Australia or Africa. If you missed my last post, it talks more about the SKA itself, what it is and what it means for science.
But now let’s talk about first light.
Our whole universe was in a hot dense state
Then nearly 14 billion years ago expansion started, wait
- Barenaked Ladies (Big Bang Theory theme song)
But before the earth began to cool and the autotrophs began to drool a lot had to happen. The creation of stars, galaxies, and all things seen and unseen has taken billions of years.
By observing cosmic microwaves we can study how the universe looked at the age of 300,000 years, smooth and uniform. Through telescopes we’ve looked back to when the universe was a billion years old, as protogalaxies merged into galaxies.
But between those times, we know very little. This period is called the dark ages, before stars were formed and started to shine.
First light is the end of the dark ages, the moments when the first protogalaxies and quasars came into existence.
How can we look back six billion years to first light? Telescopes are time machines.
Look at something near you right now, say a pen. What you’re really seeing is light bouncing off the pen, travelling through the air to your eyes. Light moves very fast, but it’s not immediate. It takes a fraction of a second for the light to reach you.
Look a bit further now. Light from our tide-turning moon takes just over a second to get to Earth. Light from our dawn-breaking ball of exploding gas, the sun, takes a leisurely eight minutes to shine upon us. The next nearest star, Proxima Centauri, is four lightyears away. Light takes four years to travel the distance separating us. You can look thousands, millions, even billions of years into history. (source: http://en.wikipedia.org/wiki/Lightyears)
The further away you look, the further into the past you gaze. I always imagine what has changed out there in the thousands of years the light has taken to reach us. Is that star still there? Is it in the throes of death, spreading out into a supernova?
First light, then, though it happened long ago we can still see it happening in celestial newly-forming bodies that are very, VERY far away.
Distant and only faintly glowing protogalaxies defy current telescope technology. Finding first light is heralded as the next frontier in cosmology.
Here’s more about the SKA projects