August 2, 2010 - Shining a Light on Dark Matter
Shining a Light on Dark Matter Dark matter makes up most of the material in the universe, while ordinary matter, which makes up stars and planets, comprises only a few percent of the material in the universe. Although dark matter itself cannot be observed directly, its existence in a galaxy cluster can be inferred by observing how its gravity bends the light of more distant background galaxies. The Hubble Space Telescope observed galaxy cluster CI 0024+17, some 5 billion light-years away, and discovered not only dark matter, but also its unexpected distribution in a ghostly ring shape, most likely caused by the long-ago collision of two clusters of galaxies. Nearly every object in the above image is a galaxy, with blue representing the distribution of the dark matter that distorts those background galaxies.
Image credit: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)
August 2-8, 2010
Holidays - Sky Events - Space History
Last Quarter Moon 12:59 AM ET
Mercury at greatest elongation (27° E)
Ceres appears stationary