The James Webb Space Telescope has performed a wonderful cosmic trick. It captured a view of a distant galaxy three times in one image, revealing the story of a star that exploded and disappeared.
Webb, a joint project from NASA, the European Space Agency and the Canadian Space Agency, received help from a galaxy cluster called RX J2129 that is about 3.2 billion light-years away from us. The cluster allows Webb to take advantage of a phenomenon called gravitational lensing, where a space object acts like a giant magnifying glass to show what’s hiding behind it.
Not only does the galaxy appear three times, but it appears at different points in time. A supernova — a bright exploding star — appears in the earliest version of the galaxy. The second and third images, from about 320 days and 1,000 days later, show that the supernova has faded. An annotated version of the image points out these cool features:
How is this action possible in the time machine? “Because the mass of the galaxy cluster is distributed unevenly, the light rays emitted by the supernova are bent by the lens by different amounts, and so they take longer or shorter paths towards to the viewer – resulting in different images,” ESA explained in a statement last week. Think of the cluster as a bumpy, uneven magnifier, which is also why the orientation and size of the galaxy are not the same in the scenes.
Astronomers originally spotted the supernova in observations from the aging Hubble Space Telescope, showing once again how Hubble and Webb can work together to help us better understand our universe.