A 2012 image reveals a galaxy cluster is creating multiple, magnified images of a distant galaxy. Is dark matter the culprit?
While studying this galaxy cluster again in November 2014, researchers captured four images of the same supernova in that galaxy.
Researchers predicted the supernova would appear again elsewhere, but their observations in October 2015 revealed nothing.
In December 2015, they looked again—and caught the supernova’s reappearance, proving some predictions were accurate.
Researchers used dark matter models to correctly predict the supernova’s reappearance, refining our understanding of its distribution.
A Story Of Dark Matter: Supernova Refsdal
Predicting the reappearance of a supernova’s light.
Scientists know more about what dark matter isn’t than what it is. Though dark matter has not been detected with telescopes, we know it exists because of its gravitational effects on objects we do see—objects that emit or reflect light. When space is warped by dark matter’s gravity, the light of distant galaxies—and bright objects within them, like supernovas—appear distorted. Using this and other methods, astronomers calculate that there is much more dark matter in the universe than matter we can currently see.
Supernova Refsdal exploded in a galaxy over 9 billion light-years away. In between this supernova and Earth is a galaxy cluster. Like all galaxy clusters, it contains abundant amounts of dark matter. The gravitational force exerted by the enormous mass of dark matter (along with the less-abundant visible matter) in the galaxy cluster distorts light from the supernova, causing the light to travel to Earth along multiple paths. This effect, known as gravitational lensing, also created multiple images of the background galaxy where the supernova exploded. Some of the paths the supernova’s light took were longer than others and took more time to travel. The case of Supernova Refsdal offered researchers the opportunity to predict when light that took a longer path—but hadn’t yet arrived at Earth—would reappear.
Scientists constructed models and made predictions about when and where the supernova’s light would reappear. (Their models varied based on their hypotheses about the dark matter’s distribution.) Researchers’ first follow-up observations showed nothing. Later observations proved a few models correctly predicted where the supernova’s light would reappear. This timely science case allowed astronomers to further refine the amount and distribution of dark matter in their models of this and other galaxy clusters.
Quick Facts: Supernova Refsdal
Also known as:
SN HFF14Ref in the MACS J1149.5+2223 galaxy cluster
Distance from Earth:
9.3 billion light-years (supernova); 5 billion light-years (galaxy cluster)
Type of object:
Supernova
Location in the sky:
Leo Constellation
Did you know:
The first observation of the supernova, which appeared four times, is known as an Einstein Cross.
Credits: Supernova Refsdal
2012 image of MACS J1149.5+2223 from the Hubble Space Telescope: NASA, ESA, W. Zheng (JHU), M. Postman (STScI), and the CLASH Team
March 2015 image of MACS J1149.5+2223 from the Hubble Space Telescope: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)
October 2015 and December 2015 images of MACS J1149.5+2223 from the Hubble Space Telescope: NASA, ESA, and P. Kelly (University of California, Berkeley); NASA, ESA, and S. Rodney (University of South Carolina) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)
Dark matter map based on A. Zitrin 2020, arXiv e-prints, arXiv:2008.10642
Subject-matter expertise provided by Dr. Patrick Kelly
Produced by the Space Telescope Science Institute’s Office of Public Outreach