Astronomers predict that a distant supernova previously imaged by the Hubble Space Telescope will be visible from Earth again in 2037.
The Requiem supernova is the result of a stellar explosion 10 billion light-years away. Because of a phenomenon known as gravitational lensing, it was visible to the legendary space observatory three times in 2016.
What is gravitational lensing?
Gravitational lensing occurs when supermassive celestial bodies bend and split light, magnifying and distorting images of objects behind them. In the case of supernova Requiem, a massive galaxy cluster known as MACS J0138.0-2155 acted as a magnifying glass, revealing the stellar explosion in three different snapshots based on the three different paths the supernova’s light took through the cluster.
The prediction that the supernova will be visible again (though not to the naked eye) is based on computer modeling of the distribution of matter within the cluster, which is 4 billion light-years from Earth.
The final display of the supernova will be delayed by more than two decades compared to the previous three sightings because the light carrying the last image must travel through the cluster’s central part, which is also the densest due to the concentration of dark matter, a team of European and American researchers said in a statement.
“This is the last one to arrive because it’s like a train that has to go deep down into a valley and climb back out again,” Steve Rodney, an astronomer at the University of South Carolina and lead scientist on the new research predicting Requiem’s return, said in the statement. “That’s the slowest kind of trip for light.”
The previous three sightings
were found by accident in Hubble’s archived data in 2019, three years after the observatory acquired the images.
Gabe Brammer, an astronomer at Denmark’s University of Copenhagen, discovered the supernova by chance while searching for unknown distant galaxies as part of an ongoing research program called REsolved QUIEscent Magnified Galaxies (REQUIEM), hence the supernova’s name.
At first, he only noticed one small dot in the 2016 images and assumed it was a galaxy hidden far behind the massive cluster and visible due to gravitational lensing.
A supernova explosion lasts only a few minutes. Its bright flash of light fades quickly and completely vanishes within a year.
Closer inspection of the images revealed that the bright dots were surrounded by dusty smears, which were most likely magnified snapshots of the supernova’s host galaxy.
Rodney, Brammer, and astronomer Johan Richard of the University of Lyon in France collaborated to investigate the event further. They created maps of the distribution of dark matter in the cluster based on the three observations to better understand how gravity bends and distorts light. In addition to the 2037 sighting, they calculated that the supernova might be visible again in 2042, but it will most likely be too faint to produce any valuable observations.
The study was published in the journal Nature Astronomy.