The Chandra X-ray Observatory orbits high above the Earth,
peering into the blackest reaches of space.
Exploring the most menacing and magnificent features of the
cosmos, this remarkable telescope is revealing what our eyes
can't, taking us beyond visible light.
Peering into the dark with its X-ray vision, NASA's Chandra X-ray Observatory is helping
to unravel one of astronomy's most perplexing enigmas.
Clusters of starlit galaxies and searing hot gas somehow stay together, even though the stars and gas
themselves don't have enough mass -- or gravity -- to explain their bond.
What cosmic ingredient is lurking in the darkness, undetectable by any of our telescopes,
holding these spinning groups together when they should be flung apart?
TANANBAUM: And, to hold the gas and the galaxies in place, you have to have this additional material.
You can compute how much there is -- it's about, again, close to 10 times more than we see in the gas and in the stars.
And this material, because it doesn't radiate x-rays, it doesn't radiate light, it doesn't radiate in the infrared –
we feel the force of its gravity, we know it's there but we can't see it. So we call it dark material, dark matter.
Light waves from normal matter can be detected by a variety of telescopes, such as optical,
X-ray, infrared, gamma-ray and more.
Dark matter, on the other hand, is visible only through its gravitational effects on the matter we can see around it.
In August 2006, Chandra and other telescopes working together found direct proof of dark
matter with a breakthrough discovery in a galaxy cluster known as the Bullet Cluster.
When the Bullet Cluster's galaxies merged, the clouds of gas slowed down due to friction,
but the galaxies themselves slipped through the collision.
TANANBAUM: The galaxies and the dark matter, they act more like individual particles,
and so they interact through the force of gravity.
But they don't behave like a gas or a fluid, and it tells us something about the interactions of the dark matter -- namely,
it doesn't interact with itself other than through the force of gravity.
And we have actually physically separated -- -we haven't personally separated, but in this Bullet Cluster –
the dark matter and gas have been separated -- and you actually can see the concentration of the dark matter
offset from the concentration of the gas. And it's a very visual demonstration that the dark matter
is real and it's different from the ordinary material, the baryons, the gas.
The mystery deepened once more in August 2007.
Chandra and optical telescopes revealed that in the Abell 520 galaxy cluster,
dark matter behaved in an opposite manner from the Bullet Cluster.
Instead of staying with the galaxies, the dark matter collected in the center of the cluster
while the bright galaxies collected outside the core.
Undaunted by this new finding, astronomers are not giving up.
VIKLINHIN: Also for studying dark matter, it's important because most of the cluster
mass turns out to be in the form of dark matter. So, clusters are so big that the composition
of the clusters is exactly the same as that of the entire universe.
Using valuable tools like Chandra, the best scientific minds are working to reveal what
dark matter really is and the role it plays in the universe.
But for now, this matter continues to keep us in the dark.