* Astronomy

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RE: Gravitational lensing

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Astronomers Find Cosmic Lenses with Feeding Black Holes

In space, it sometimes happens that two galaxies are aligned in just the right way that the closer galaxy distorts and magnifies the appearance of the one behind it. For astronomers, finding these alignments is like coming across giant, cosmic magnifying glasses.
Now, a team of astronomers, including Daniel Stern from NASA's Jet Propulsion Laboratory in Pasadena, Calif., has found several rare examples of this phenomenon, called gravitational lensing, in which the foreground galaxy hosts an actively accreting supermassive black hole.
Such feeding black holes, called quasars, are among the brightest objects in the universe, far outshining the total starlight of their host galaxies. Because they are so bright, it is hard for astronomers to measure the mass of their host galaxies. However, gravitational lenses are invaluable for estimating the mass of a quasar's host galaxy. The amount of the background galaxy's distortion can be used to accurately measure the lensing galaxy's mass.
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Quasar Gravitational lensing

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RE: Gravitational lensing

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A Duke University professor and his graduate student have discovered a universal principle that unites the curious interplay of light and shadow on the surface of your morning coffee with the way gravity magnifies and distorts light from distant galaxies.
They think scientists will be able to use violations of this principle to map unseen clumps of dark matter in the universe.
Light rays naturally reflect off a curve like the inside surface of a coffee cup in a curving, ivy leaf pattern that comes to a point in the center and is brightest along its edge.

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"To see a world in a grain of sand, And a heaven in a wild flower, Hold infinity in the palm of your hand, And eternity in an hour" - William Blake.

Blobrana · L

Author: Arlie O. Petters

My research deals with the mathematical and physical aspects of gravitational lensing, which is the action of gravity on light. In a typical gravitational lensing scenario, light originates from a distant source like a star, galaxy, or quasar, and experiences deflection by the gravity of a foreground mass before arriving on earth. The deflector could be a star, galaxy, clump of dark matter, or even a black hole.
The earliest scientific papers on gravitational lensing date back to at least the early 1780s, when Michel, Laplace, and Cavendish applied Newton's theory of gravity to lensing. However, it was not until 1915 that Einstein, using his brand-new gravitational theory - The General Theory of Relativity - derived the correct formula for how much gravity bends light. His prediction for the bending angle of starlight grazing the sun, which is twice the angle obtained via Newton's gravitational theory, was confirmed in 1919 by Sir Arthur Eddington. This marked the first observed example of gravitational lensing. The turning point in the subject, though, was triggered by the 1979 discovery of lensing outside our solar system. Since then hundreds of examples of extra-solar gravitational lensing events have been observed and the field has undergone exponential growth.
Today, gravitational lensing attracts astronomers, astrophysicists, mathematical physicists, and mathematicians across the globe. Lensing is exciting because it can address the nature of dark matter, the existence of extra-solar planets, the existence of black holes, the existence of a possible extra dimension of physical space, etc. My work straddles and creates synergistic interactions between the mathematical and physical aspects of the subject.

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