Telstra has revealed the addition of almost one million new mobile services in the six months to December 2011, but Sensis revenues plummeted 24 percent in 12 months.
A gravitational lens (a circle) is formed when radiation (light) from a very distant and bright source (like a quasar, or in this particular case, a galaxy) is curved (bent) around a massive object (like a galaxy). We see this bending of light when we are looking at the pair of objects directly on a straight line between us and the two objects.
In other words, we would miss this phenomenon if we aren’t positioned just in a straight line with the other two objects. However, an alien civilization would be able to see it if its astronomers are observing the two objects and they are in line with these two objects.
The process is called gravitational lensing because gravity from the closer object causes the bending of light from the more distant object, and because the whole concept is kinda like the lens of a magnifying glass.
The lens itself is called an 'Einstein ring' because its formation was predicted by the 1936 general theory of relativity, first proposed by German-American physicist Albert Einstein. At that time, Einstein proposed that the gravitational field from massive objects, such as galaxies, could warp space and curve light. He didn’t think it was possible to directly observe such warping of space.
However, since Einstein’s time we have developed much more advanced telescopes.
For more information on gravitational lensing and Einstein rings, and the work being done in the field with the Sloan Lens Advanced Camera for Surveys (SLACS) program and the Hubble Space Telescope, go to the article “Hubble, Sloan Quadruple Number of Known Optical Einstein Rings.”
In this case, the gravitational lensing is comprised of a double Einstein ring because two lenses are produced from the two distant galaxies directly behind the foreground galaxy (the one about three billion light-years away). The middle galaxy (the one about six billion light-years away) forms the inner ring and the most distant galaxy (the one about eleven billion light-years away) forms the outer ring.
Tommaso stated that they “hit the jackpot” by the very rare chance of seeing a double Einstein ring.
The double Einstein ring allowed astronomers to measure the mass of the middle galaxy. They found it to be of a mass of about one billion solar masses (the mass of about 1,000,000 Suns).
The researchers state that if they could find numerous other double Einstein rings, then they could measure the curvature of space by gravity, and compare it their current estimate of the curvature of space.
A comparable number of double Einstein rings could also help astronomers measure the amount of dark matter in the universe. A proposed NASA/Department of Energy Joint Dark Energy Mission (JDEM) is being recommended for such a research project. It may consist of three parts: the Advanced Dark Energy Physics Telescope (ADEPT), the SuperNova/Acceleration Probe-Lensing (SNAP-L), and the Dark Energy Space Telescope (Destiny).
The astronomical team consisted of: Raphael Gavazzi and Tommaso Treu (University of California, Santa Barbara), L. Koopmans (Kapteyn Astronomical Institute, The Netherlands), A. Bolton (Institute for Astronomy, University of Hawaii/Harvard-Smithsonian Center for Astrophysics), L. Moustakas (Jet Propulsion Laboratory/Caltech), S. Burles (Massachusetts Institute of Technology), and P. Marshall (University of California, Santa Barbara).
David Bass
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