Dark matter is the universe’s biggest mystery. Astronomers can tell that there is something invisible in the spaces between stars, since it’s creating enough of a gravitational pull to bend starlight as it travels toward Earth. However, no one knows what dark matter looks like or what it is made from.
IT’S A MYSTERY
Five percent of the visible universe of stars and planets is normal matter. However, this matter would not have enough gravitational pull to hold the galaxies together, so astronomers know that there must be another kind of matter, even if it’s invisible. Dark matter isn’t made of atoms and does not reflect light or any other kind of radiation, but it appears to make up a quarter of the matter in the universe.
MAPPING IT OUT
This computer simulation shows how dark matter is spread throughout the universe. The yellow areas show the highest concentrations of dark matter. These regions have enough gravity to pull together visible matter, creating galaxies.
What’s the matter?
This image of a distant galaxy cluster shows a ring of dark matter around its center. The ring would not normally be visible, but we can tell where it is from the way that the gravity of dark matter bends the light of distant galaxies.
The Bullet Cluster
The Bullet Cluster was formed when two galaxy clusters collided, one tearing through the middle of the other like a bullet. The cluster’s normal matter (which appears pink here) has been slowed down in the collision by a drag force. However, the dark matter has continued to move outward without slowing, creating a light-bending aura.