Prophecies about the appearance of new stars in the sky are usually found in a mythical context. Now, however, a working group headed by Stephen A. Rodney of the University of South Carolina at Columbia is also trying to do so in the field. As the team writes in “Nature Astronomy”, a supernova will light up around 2037. However, those predictions are a bit deceptive: the team has already seen the star explode – presumably a Type Ia supernova. It occurred behind a group of galaxies, which acts as a gravitational lens and creates multiple images of the explosion that become visible at intervals. Three supernova images have already appeared one after another – but the fourth is still 16 years away.
There will surely be a fourth picture. Because the AT 2016jka supernova occurred in the galaxy MRG-M0138, there are four images of it, all created by the gravitational force of a relatively nearby galaxy cluster in the foreground. Like a lens, this bends the rays of light emitted by the galaxy around it, so that several images appear in different directions. According to the Rodney team’s report, the new light source could not have been seen in the 2019 images, and then appeared in three images of the galaxy one after the other within 200 days. The fact that the images appear at different times is simply due to the fact that the paths of light have different lengths. Because, of course, a galaxy cluster is not a perfect lens, but a lumpy body that pushes rays of light down complex curved paths.
And the longest path seems to have the light behind it that belongs in the fourth picture – it’s a little closer to the center of the pile than the other three. Galaxies are closest to the center and most changes in their path are imposed on the light. To figure out how long that light lasts, the working group modeled the approximate mass distribution of the galactic crowd. For this calculation, in addition to the location of the galaxy and its four images, I also used another background galaxy, the light of which is also deflected several times by the cluster.
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