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exmarine
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I am reading papers about dark matter and MOND. As they often mention this effect, I wonder how they know / measure / quantify how much gravitational lensing a particular galaxy causes?
Thanks.
Thanks.
exmarine said:And I don’t suppose there is an Einstein ring or cross around every galaxy.
exmarine said:And how would one trace the rays when we can’t know precisely where the objects behind the galaxies are located?
phinds said:It's not measured, it's observed. Google "Einstein Rings".
Yeah I was really thinking more of "calculate" than measure, as in "calculate in advance" meaning BEFORE you observe.Drakkith said:I dunno. Seems like you can easily do a measurement from your observations.
Gravitational lensing is measured by observing the distortion of light from a distant object caused by a massive object in between, such as a galaxy or a cluster of galaxies. This distortion can be seen as a bending or stretching of the light, and the amount of distortion can be used to calculate the strength of the gravitational lensing effect.
Astronomers use several tools to measure gravitational lensing, including telescopes, cameras, and software algorithms. Telescopes, such as the Hubble Space Telescope, are used to observe the distorted images of distant objects. Cameras, such as those used in the Dark Energy Survey, are used to capture high-resolution images of these distorted objects. Finally, specialized software algorithms are used to analyze the images and calculate the amount of gravitational lensing.
Gravitational lensing is a valuable tool for measuring the amount of dark matter in a galaxy cluster. By observing the distortion of light from background galaxies, astronomers can calculate the amount of mass in the cluster that is causing the distortion. This mass is primarily made up of dark matter, as it does not emit or absorb light like regular matter does.
Yes, gravitational lensing can be used to study the properties of dark energy, which is thought to be responsible for the accelerating expansion of the universe. By observing the distortion of light from distant objects, astronomers can map out the distribution of dark matter in the universe. This can provide clues about the effects of dark energy on the growth of large-scale structures in the universe.
The accuracy of measurements of gravitational lensing depends on several factors, such as the quality of the observations, the complexity of the lensing system, and the precision of the software algorithms used to analyze the data. In general, measurements of gravitational lensing are quite accurate, with most studies reporting uncertainties of less than 10%. With advancements in technology and techniques, these measurements are becoming even more precise.