- 3856 - GRAVITY WAVES - paths of light beams? - Relativity has really tangled up the light from a distant Quasar. In 1979, astronomers spotted two nearly identical quasars that seemed close to each other in the sky. These so-called “Twin Quasars” are actually separate images of the same object.
----------------- 3856 - GRAVITY WAVES - paths of light beams?
- Even more intriguing: the light paths that
created each image traveled through different parts of the cluster. One path
took a little longer than the other. That meant a flicker in one image of the
quasar occurred 14 months later in the other. The cluster’s mass distribution
formed a lens that distorted the light and drastically affected the two paths.
-
- In 2022, astronomers reported a similar
effect with another distant quasar. They spent fourteen years measuring an even
longer time delay between multiple images of their target quasar. The galaxy
cluster SDSS J1004+4112 plays a role in the delay. The combo of galaxies and
dark matter in the cluster is really entangling the quasar light as it passes
through. That’s causing the light to travel different trajectories through the
gravitational lens.
-
- The four images of the quasar that we observe
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, they have to wait
6.73 years for the signal they observed in the first image to be reproduced in
the fourth one.
-
- The Sloan Digital Sky Survey first
discovered cluster SDSS J1004+4112. Hubble Space Telescope imaged it in 2006.
It was the first image of a single quasar with its light split into five images
by lensing.
-
- The observed time delay gives us some
interesting clues about lensing clusters. Galaxy clusters are astonishingly
massive and the largest gravitationally bound structures we know of in the
universe. Some contain thousands of galaxies.
-
- The combined gravity of the galaxies, plus
the intermingled dark matter in the cluster can entangle light from more
distant objects as it passes through or near the cluster. The mass in the cluster is spread out
unevenly. That can affect the path of light through the cluster.
-
- Measuring these time delays helps to better
understand the properties of galaxies and clusters of galaxies, their mass, and
its distribution. In addition to the
mass distribution, observational data also helps understand other
characteristics of the lensing cluster.
-
- 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.
-
- Calculating the time delay also allows
other discoveries, including the distribution of stars and other objects in the
area of space between galaxies in the cluster. It will help astronomers to
calculate the size of the distant quasar’s accretion disk.
-
- The observations occurred over 14.5 years
at the 1.2-meter telescope located at the Fred Lawrence Whipple Observatory, in
collaboration with scientists at The Ohio State University.
-
January 31, 2022 GRAVITY
WAVES - paths of light beams? 3856
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--------------------- --- Wednesday, February 1, 2023 ---------------------------
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