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Posts Tagged ‘gravitational lens effect’

In a paper to be published in Astronomy and Astrophysics, available online now here, astronomers have concluded that exoplanetary moons should be detectable using orbiting satellite telescopes and a technique known as gravitational microlensing. This technique, a refinement of gravitational lensing, applies Einstein’s General Theory of Relativity and its curvature of space effect on the path that the light will follow. Although the technique has only been used to discover a very small percentage of the 430 or so known exoplanets, it apparently may be ultimately used to discover moons orbiting exoplanets, where the other techniques cannot accomplish this feat. The paper is provides the reader an excellent overview of gravitational lensing, gravitational microlensing and its link to the experiments done almost a century ago to first demonstrate that Einstein’s General Theory of Relativity was correct.

In a white paper released yesterday, available online now here, astronomers address the question of where in the sky would be good candidates for observing the micro-lensing effects of exoplanets. Gravitational micro-lensing is a technique which utilizing the General Relativisitic effect that gravity has on light, allowing any massive object to act like a lens if directly in line with light from a more distant object. The authors argue that “out of the five popular planet detection techniques,
Gravitational Microlensing is the most capable of detecting rocky, earth-sized planets and seems to be more promising in the search for other habitable worlds.” Thus, they offer to astronomers “a distribution map for probability of finding stars within the Milky Way Galaxy that could harbor terrestrial planets capable of hosting life, with a particular emphasis on the Microlensing detection of exoplanets.”

The gravitational lens effect (bending of light by gravity) was first predicted by Einstein with his General Theory of Relativity. It was originally demonstrated shortly after the World War I utilizing our Sun at the time of a total solar eclipse. It has since been instrumental in investigating the most distant galaxies in the universe. Learn about the latest gravitational lensing analyses of distant galaxies online at http://xxx.lanl.gov/PS_cache/arxiv/pdf/0812/0812.3934v1.pdf This group of astronomers utilized the Sloan Digital Sky Survey. You can see images from this bright arc survey online at http://home.fnal.gov/~kubo/brightarcs.html The most distant of the galaxies discussed are estimated to be close to 8 billion light years distant.

Yesterday, scientists from the California Institute of Technology (CalTech)  announced that they had successfully measured the rotation rate of a very  distant galaxy.  They utilized a technique predicted by Einstein’s General Theory of Relativity, called the gravitational lens effect.  This is when the space around a very massive object, like a giant elliptical galaxy, warps space like a rubber sheet, and can give the effect just like a lens bending light between the observer and the more distant object, in this case an even more distant galaxy. By utilizing the gravitational lens effect like a magnifying glass, a galaxy about 6 billion light years distant was able to be used to view a galaxy about 11 billion light years distant.  The detail was so fine as to allow the detection of the more distant galaxy’s rotation rate, utilizing what is known as the Doppler Effect (just like when you are standing at a train platform and notice the change in pitch of the sound coming from a train that approaches the station and then passes you by) applied to spectral lines from the more distant galaxy. The rotation of a galaxy aids astronomers in their study of how galaxies change in form over time.
Read more about this at http://mr.caltech.edu/media/Press_Releases/PR13190.html
Learn about the gravitational lens effect at
http://imagine.gsfc.nasa.gov/docs/features/news/grav_lens.html and get a feel for rotation curves at
http://imagine.gsfc.nasa.gov/docs/teachers/galaxies/imagine/act_rotation.html
You can also learn about the Doppler Effect at
http://imagine.gsfc.nasa.gov/YBA/M31-velocity/Doppler-shift-2.html