Hello, my name's Dr Greg Brown, I'm one
of the Astronomers here at the Royal Observatory
Greenwich.
Our night sky is absolutely filled with stars.
Using powerful telescopes, we can see that the
universe it filled with vast collections of
stars called galaxies - these cities of stars
in the void of otherwise empty space.
But we also know that our universe was not
always this way. About 14 billion years ago,
our universe began in an event called the
big bang. At this time, our universe was a
super dense, super hot lump.
The big bang began the expansion of our universe.
The material in it began to spread out and
cool down.
After a long period of darkness called the
Cosmic Dark Ages, eventually the material
cooled down enough to clump together and begin
to form the first stars.
These stars were huge, many times larger than
our own sun. They were exceptionally hot and
very short lived - much shorter than most
of the stars that exist in the universe today.
An ongoing part of Astronomy research has
been to try and find these first stars. Unfortunately,
things have been working against us. One thing,
the light from these stars is no longer in
the visible range that our eyes can see. It's
instead in radio light - it's been stretched
out by the expansion of the universe. Also,
our own galaxy is working against us. The
signal coming from these stars is about one
ten thousandth the noise coming from our own
galaxy.
And yet, despite the odds, it seems that Astronomers
led by Judd Bowman from Arizona State University,
may have found the signal of these elusive
first stars. The signal itself is a slight
absorption, a slight dip in radio light, that's
associated with hydrogen gas - the most common
element in the universe. Interestingly, the
signal that they found was much stronger than
they expected, indicating that the hydrogen
gas was absorbing more light than we expected
it to, which means that the hydrogen gas must
have been colder than we expected it to be.
So how did the universe cool down this quickly?
Well, one Astronomer, Rennan Burkina of Tel
Aviv University, suggests that it might be
an interaction between this hydrogen gas in
the early universe and something called dark
matter. Dark matter is an a very elusive,
very unusual, enigmatic substance that nonetheless
makes up 80% of all the stuff, all the matter,
of our universe. Unfortunately, we have no
idea what it's made out of. This observation
though, suggests that particles of dark matter
must be smaller than initial models suggested.
So maybe with a few more detections and a
few more discoveries like this, we'll finally
find out what dark matter is.
But don't worry if you're wondering if we're
running out of questions to ask in Astronomy
- the vast majority of energy in the universe
is something called dark energy, and we have
absolutely no idea what that is. Thanks for
listening.
