- 3703 - GRAVITY LENS - multiple images of quasar? When astronomers measured multiple image of the same quasar, they measured a time delay of 6.73 years, the longest ever detected for a gravitational lens, between multiple images of a quasar. After 14.5 years this observation will improve knowledge about galaxy clusters and the dark matter they contain.
--------------------- 3703 - GRAVITY LENS - multiple images of quasar?
- Galaxy clusters are the largest gravitationally bound structures in the universe and can contain thousands of galaxies. In addition to galaxies and gas, the clusters are mostly made up of dark matter of a still unknown nature.
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- Astronomers use quasars which are the brightest astronomical objects in the universe as ‘gravitational lenses’. Gravitational lensing occurs when a massive object is between the observer and a bright celestial body. The massive object warps space-time and modifies the path of light rays passing through it.
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- When observing a distant quasar through a galaxy or cluster of galaxies, if the lensing effect is strong enough, several images of the same celestial body are formed.
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- The observations were carried out over 14.5 years with the 1.2 m telescope located at the Fred Lawrence Whipple Observatory (FLWO) of the Harvard-Smithsonian Center for Astrophysics, in collaboration with scientists at The Ohio State University.
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- The four images of the quasar actually correspond to a single quasar whose light is curved on its path towards us by the gravitational field of the galaxy cluster. Since the trajectory followed by the light rays to form each image is different, they observe them at different instants of time; in this case we have to wait 6.73 years for the signal we observed in the first image to be reproduced in the fourth one.
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- Measuring these time delays helps to better understand the properties of galaxies and clusters of galaxies, their mass and its distribution, in addition to providing new data for the estimation of the “Hubble constant‘ of the universe’ rate of expansion .
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- This time delay has made it possible to more accurately reconstruct the mass distribution of the galaxy cluster that acts as a lens. It has been possible to constrain the distribution of dark matter in the inner region of the cluster, since the lensing effect is sensitive not only to ordinary matter but also to dark matter.
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- Measured time delays are used to determine the distribution of stars and other compact objects in the intra-cluster medium, as well as to calculate the size of the quasar’s accretion disk. These calculations contribute to advancing our understanding of the formation of structures and their evolution in the universe.
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October 8, 2022 GRAVITY LENS - multiple images of quasar? 3703
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