- 3725 - DARK MATTER - measuring the mass of galaxies? 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.
--------------- 3725 - DARK MATTER - measuring the mass of galaxies?
- Astronomers measured a time delay of 6.73 years, the longest ever detected for a gravitational lens, between multiple images of a quasar. This result after 14.5 years of observation will improve knowledge about galaxy clusters and the dark matter they contain.
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- 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, imperceptible by direct detection of light, of a still unknown nature.
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- When observing a distant quasar through a galaxy or cluster of galaxies, if the gravitational lensing effect is strong enough, several images of the same celestial body are formed. The observations were carried out over 14.5 years with the 1.2 meter 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 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, we 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.
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- 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 assures that the calculation of the time delay. This allows astronomers to determine the distribution of stars and other compact objects in the intracluster medium, as well as to calculate the size of the quasar’s accretion disk.
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October 29, 2022 DARK MATTER - measuring the mass of galaxies? 3722
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