Refsdal supernova was calculated from different models of the galaxy cluster.
By Dileep Thekkethil
Once again Hubble has done a remarkable job by capturing the image of the first-ever predicted supernova explosion in a distant galaxy.
According to the official website of Hubble Telescope, the supernova, nicknamed Refsdal, was spotted in the galaxy cluster MACS J1149.5+2223. The supernova exploded some 10 billion years ago killing thousands of nearby stars but it took the light five billion years to reach our solar system.
The website says: “The reappearance of the Refsdal supernova was calculated from different models of the galaxy cluster whose immense gravity is warping the supernova’s light.”
According to NASA, many stars during their final years turn into a supernova and with a big bang burst into flames, devouring everything nearby. But only few such incidents have been spotted, through sheer luck. But now, NASA has the first image of a supernova exploding, which was predicted way in advance.
NASA started observing Refsdal in November 2014 when scientists took note of an anomaly in the images of the supernova in a rare arrangement known as Einstein Cross around the galaxy, in MACS J1149.5+2223.
“While studying the supernova, we realized that the galaxy in which it exploded is already known to be a galaxy that is being lensed by the cluster,” explains Steve Rodney, co-author, from the University of South Carolina.
He added: “The supernova’s host galaxy appears to us in at least three distinct images caused by the warping mass of the galaxy cluster.”
The multiple images taken by Hubble enabled the astronomers to study the galaxy in detail as the images taken during different times take different paths, which will make the supernova appear at different intervals.
By using the lensed galaxies (a lenses like effect around a galaxy produced by gravity capable of bending the light from the source) and combining the Einstein Cross event that happened in 2014, astronomers predicted the precise time the supernova would reappear. The astronomers also claim that the event had happened before in 1998 but no telescope was able to detect the anomaly in the galaxy.
“We used seven different models of the cluster to calculate when and where the supernova was going to appear in the future. It was a huge effort from the community to gather the necessary input data using Hubble, VLT-MUSE, and Keck and to construct the lens models,” explained Tommaso Treu, lead author of the modelling comparison paper, from the University of California at Los Angeles.
He added: “And remarkably all seven models predicted approximately the same time frame for when the new image of the exploding star would appear”.
Hubble has been peeping into the galaxy cluster that holds the supernova since October, hoping to find the reappearance of the explosion as predicted by the astronomers. On December 11, Refsdal replayed it final moments that happened 10 billion years ago.
“Hubble has showcased the modern scientific method at its best,” commented Patrick Kelly, lead author of the discovery and re-appearance papers and co-author of the modelling comparison paper from the University of California, Berkeley. “Testing predictions through observations provides powerful means of improving our understanding of the cosmos.”
The reappearance of the supernova and its explosion caught on camera has made a landmark opportunity for the scientists to test the different models of how mass especially the dark matter that is distributed with in galaxy clusters.
NASA’s Hubble telescope is aging and nearing its days of decommissioning but its the best surveillance eye in space, at least for now. Hubble was launched into low Earth orbit in 1990, and has completed 25 years, 7 months and 23 days looking into distant galaxies.
The James Webb Space Telescope, which is scheduled to launch in October 2018, is touted as the successor instrument to the Hubble Space Telescope and the Spitzer Space Telescope.