Peter Kurczynski: Astronomers have discovered
evidence
of the first light from some of the first stars,
among the farthest and oldest physical objects
in the universe.
Using a simple radio antenna,
and a great deal of careful measurement,
they have effectively seen farther back
than even the Hubble Space Telescope.
These stars emerged
from the smoldering embers of the Big Bang.
They lit the sky for the first time
and the early cosmos began to transform
from an era of pitch-black emptiness,
astronomers call the Dark Ages,
into the brilliant menagerie of galaxies, stars and planets
that we now recognize.
Their discovery was not done
with a huge, complex observatory,
but with, THIS.
An antenna not much larger than a table-top.
More than 12 years ago,
a small team of investigators
including Alan Rogers and Judd Bowman,
a graduate student at the time,
realized that such an antenna coupled
with an exquisitely sensitive receiver
could probe the early universe.
As a post-doc, Judd proposed to the National Science Foundation
to build this experiment.
The Foundation took a risk on this innovative idea.
For Alan, here was a challenge that would test his experience
making sensitive radio-wave measurements against a signal
that some experts thought would be impossible.
Too faint to find.
Alan disagreed.
He thought it could be done.
Before the first stars, the universe was dark, cold.
A tenuous and unlit gas of mostly hydrogen,
awash in a sea of background radiation.
A cosmic afterglow from the Big Bang
that included some radio waves.
Astronomers theorized that starlight from the first stars
to light up the universe would excite this hydrogen gas
and cause it to absorb the surrounding radio waves
at one particular frequency.
Problem is, due to the expanding universe,
this absorption would be observed
at some lower frequency, unknown.
Finding that frequency, finding the absorption
that comes when the first stars turn on would be like listening
to every station on your car stereo at once
and being able to tell that your favorite one is missing.
Alan and Judd realized that a small team,
armed with their single antenna and sensitive receiver,
might be enough to detect the signal
not from a particular direction
but averaged over the whole sky.
They would need to set up in a remote place,
far from radio interference.
So They traveled to the desert of Australia
to deploy their antenna and listen to the sky.
But even in such a pristine location,
this signal is fantastically faint.
Our galaxy alone is booming with radio-wave noise
10,000 times louder
than any faint whisper from the distant universe.
For Alan, Judd and their team,
finding the impact of the first stars in that cacophony
would be like trying to hear the flap of a hummingbird’s wing
from inside a hurricane.
After several years of improving their apparatus,
they found hints of a signal in early 2016.
But, given the excruciating challenge of detection,
how could they be sure it was real?
Good science is an adventure;
but it is also careful and methodical.
So the team spent more than a year ruling out other possible
explanations for what they had found.
They expanded the ground plane beneath their antenna.
They deployed a second antenna. They changed its orientation.
They improved the calibration.
They even ruled out interference from the Sun and the moon.
In the end, their detection remained, it was real.
With this new discovery to guide them,
large research collaborations will hunt for
and study variations in the hydrogen signal
and map the early universe in minute detail.
These experiments will use arrays of hundreds of antennas
and complex data processing, and hundreds of hours of observing.
Those collaborations were conceived
before knowing for sure
if that signal could ever be found,
and if so, at precisely what frequency.
Now, thanks to Alan, Judd and their team, they know.
Astronomers are filling in a missing chapter
in how the universe evolved from the Big Bang.
We are piecing together how, over billions of years,
matter evolved from this into this.
In a surprise twist to the story,
the signal this team has found
is twice as large as models predicted.
Meaning that absorbing gas in the early universe
was colder than we thought possible.
Could dark matter provide an explanation?
Maybe. Either way, with this discovery,
now we know when the universe
emerged from the Dark Ages into Cosmic Dawn.