A cluster of galaxies could delay the flicker of a quasar by seven years
Quasars are kinds of very massive black holes and very bright, detected at the center of a cluster of galaxies. These clusters of galaxies are gravitationally bound and may contain thousands of galactic formations. Astronomers have spotted two quasars almost identical in 1979. However, these “twin quasars” are two distinct images of the same celestial object.
Furthermore, by the path of light rays between galaxies, one image was 14 months behind the other. The mass distribution of the galactic cluster formed a gravitational lens which distorted the trajectories of light rays.
In 2022, a team of astronomers from the University of Valencia reported similar effects on a another distant quasar.
Galactic clusters have formed a gravitational lens capable of deflecting light
Located in galaxy cluster SDSS J1004+4112, the quasar’s flicker is hampered by the combination of galaxies and dark matter. The light beams follow different trajectories through the gravitational lens and the images observed on Earth are shifted in time.
José Antonio Muñoz Lozano, professor of the Department of Astronomy and Astrophysics and Director of the Astronomical Observatory of the University of Valencia, is one of the authors of this study. He said his team has observed four images of the same quasar.
A single quasar returned four images shifted by seven years
Moreover, as his light is bent in its path towards Earth by the gravitational field of the galaxy cluster, each image corresponds to different times. Spanish astronomers have spent no less than 14 years studying the other quasar.
Some images they observed were 6.73 years late. This is the longest deviation ever detected for a gravitational lens. This is the time required for the signal observed on the first image to be reproduced on the fourth.