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Astronomy Talk: Gravitational Lensing

Tucker Jones is discussing the lensing effect can cause galaxies to be magnified in apparent size and brightness by factors of more than 10. Viewed through Keck's adaptive optics, gravitational lens systems reveal the formation history of galaxies like our own Milky Way.
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Weak Lensing Gains Strength

Weak gravitational lensing is a uniquely promising way to learn how much dark matter there is in the Universe and how its distribution has evolved since the distant past. New work by a team led by a cosmologist from the U.S. Department of Energy's Lawrence Berkeley National Laboratory has made major progress in extending the use of gravitational lensing to the study of much older and smaller structures than was previously possible.
Until recently, weak lensing had been limited to calculating the total mass of relatively nearby groups and clusters of galaxies. Their total mass includes both ordinary, visible matter like stars and dust - what astronomers call "baryonic" matter - plus the much more massive invisible concentrations of dark matter that form groups and clusters by pulling galaxies together.
Astronomers were able to establish an important scaling relationship for nearby clusters between their total masses, determined by gravitational lensing, and the brightness of their x-ray emissions, an indication of the mass of the ordinary matter alone. A new study in the Astrophysical Journal (ApJ) now continues this important relationship to distant objects.

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Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved.
Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Centre for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.

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