Dark matter, although invisible, makes up most of the
universe’s mass and creates its underlying structure. Dark matter’s gravity drives normal matter (gas and
dust) to collect and build up into stars and galaxies. Although astronomers
cannot see dark matter, they can detect its influence by observing how the
gravity of massive galaxy clusters, which contain dark matter, bends and
distorts the light of more-distant galaxies located behind the cluster.
As seen in this
image, large galaxy clusters contain both dark and normal matter. The immense
gravity of all this material warps the space around the cluster, causing the
light from objects located behind the cluster to be distorted and magnified.
This phenomenon is called gravitational lensing. This sketch shows paths of
light from a distant galaxy that is being gravitationally lensed by a
foreground cluster.
In 1609, visionary scientist Galileo Galilei turned the newly invented
optical device of his day — the telescope — to view the heavens. Almost
four centuries later, the launch of NASA’s Hubble Space Telescope aboard
the space shuttle Discovery in 1990 started another revolution in astronomy.
Developed as a partnership between the United States space program and the
European Space Agency, Hubble orbits 340 miles above Earth’s surface.
Image Credit: NASA/ESA
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