Three very small figurines appeared in 2016 (left), but not in 2019 (right). (NASA/ESA)
Astronomers can predict the star’s explosion because the light from the supernova reached Earth earlier through other methods, thanks to the so-called gravitational lensing effect.
Mass supernovas, as they are called, exploded about 10 billion years ago in a galaxy far, far away. Light from the supernova was deflected and amplified during its long journey to Earth by the gravitational pull of a massive galaxy cluster (MACS J0138.0-2155) located between the distant galaxy and Earth. The image of the background galaxy split into four and was severely distorted.
In 2016, three of those four images (also called “arcs”) showed the asterisk, as Gabe Brammer of the University of Copenhagen in Denmark discovered in archival images from the Hubble Space Telescope. Brammer realized that they must be three separate images of a supernova explosion. Because light from those three frames reached Earth along different routes, with slightly different travel times, the three supernova frames would not have appeared at the same time, but the older Hubble images did not provide any information about these time differences.
However, based on a model of the mass distribution in the foreground cluster, astronomers have now estimated that the supernova should glow again in 2037, in the fourth frame of the distant galaxy. From the observations that will undoubtedly be made by then, astronomers can glean information not only about the distribution of visible and dark matter in the cluster, but also about the distances of both the cluster and the background galaxy. The analysis and ‘Forecast’ were published on March 13 at natural astronomy.
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