UBC astronomer makes first map of dark matter
Published Thursday, January 10, 2008 5:24PM PST
For the first time, a team of UBC scientists have mapped the elusive "dark matter" in a supercluster of stars in the night sky.
The otherwise undetectable matter -- whose mass and gravitational pull play a huge role in the movement of stars -- was mapped by showing how it distorted the space around it, said Catherine Heymans, an astronomer at UBC.
"For the first time we are clearly detecting irregular clumps of dark matter in a supercluster," said Heymans, who presented her findings to the American Astronomical Society in Austin, Texas Thursday.
Dark matter is a cosmic mystery -- though it has detectable mass, that mass doesn't emit any light, so it's as dark as a black hole.
But there is so much of it in the universe that its gravitational effects play a huge role in how things in space move, acting like an invisible web that houses galaxies.
As the universe evolves, the gravitational pull of this unseen matter causes galaxies to collide and swirl into superclusters, the largest structures in the cosmos.
Heymans trained NASA's Hubble Space Telescope to an area of the sky approximately the size of the full moon, at the supercluster Abell 901/902, a cluster 2.6 billion light-years from Earth that measures more than 16 million light-years across.
That's where they saw dark matter's unique signature: an otherwise unexplainable warping of space, said study co-author Ludovic Van Waerbeke.
"A circular galaxy will become distorted to resemble the shape of a banana if its light passes near a dense region of dark matter," he said.
To reach Earth, the light from galaxies behind the Abell supercluster have to travel through it and be bent by its massive gravitational field.
Heymans measured the distorted shapes of 60,000 of those faraway galaxies to find where the dark matter pooled into dense clumps, totalling 10 trillion times the Sun's mass.
These areas match the known location of hundreds of old galaxies that have been smashed together in their passage from the outskirts of the supercluster into these dense regions.