Rerun of supernova blast expected to appear in 2037
IMAGE: NOW YOU SEE THEM, NOW YOU DON'T. THREE VIEWS OF THE SAME SUPERNOVA APPEAR IN THE 2016 IMAGE ON THE LEFT, TAKEN BY THE HUBBLE SPACE TELESCOPE. BUT THEY'RE GONE IN THE 2019 IMAGE. THE DISTANT SUPERNOVA, NAMED REQUIEM, IS EMBEDDED IN THE GIANT GALAXY CLUSTER MACS J0138. THE CLUSTER IS SO MASSIVE THAT ITS POWERFUL GRAVITY BENDS AND MAGNIFIES THE LIGHT FROM THE SUPERNOVA, LOCATED IN A GALAXY FAR BEHIND IT. CALLED GRAVITATIONAL LENSING, THIS PHENOMENON ALSO SPLITS THE SUPERNOVA'S LIGHT INTO MULTIPLE MIRROR IMAGES, HIGHLIGHTED BY THE WHITE CIRCLES IN THE 2016 IMAGE. THE MULTIPLY IMAGED SUPERNOVA DISAPPEARS IN THE 2019 IMAGE OF THE SAME CLUSTER, AT RIGHT. THE SNAPSHOT, TAKEN IN 2019, HELPED ASTRONOMERS CONFIRM THE OBJECT'S PEDIGREE. SUPERNOVAE EXPLODE AND FADE AWAY OVER TIME. RESEARCHERS PREDICT THAT A RERUN OF THE SAME SUPERNOVA WILL MAKE AN APPEARANCE IN 2037. THE PREDICTED LOCATION OF THAT FOURTH IMAGE IS HIGHLIGHTED BY THE YELLOW CIRCLE AT TOP LEFT. THE LIGHT FROM SUPERNOVA REQUIEM NEEDED AN ESTIMATED 10 BILLION YEARS FOR ITS JOURNEY, BASED ON THE DISTANCE OF ITS HOST GALAXY. THE LIGHT THAT HUBBLE CAPTURED FROM THE CLUSTER, MACS J0138.0-2155, TOOK ABOUT FOUR BILLION YEARS TO REACH EARTH. THE IMAGES WERE TAKEN IN NEAR-INFRARED LIGHT BY HUBBLE'S WIDE FIELD CAMERA 3. view more
CREDIT: CREDITS: IMAGE PROCESSING: JOSEPH DEPASQUALE (STSCI)
It's challenging to make predictions, especially in astronomy. There are however, a few forecasts astronomers can depend on, such as the timing of upcoming lunar and solar eclipses and the clockwork return of some comets.
Now, looking far beyond the solar system, astronomers have added a solid prediction of an event happening deep in intergalactic space: an image of an exploding star, dubbed Supernova Requiem, which will appear around the year 2037. Although this rebroadcast will not be visible to the naked eye, some future telescopes should be able to spot it.
It turns out that this future appearance will be the fourth-known view of the same supernova, magnified, brightened, and split into separate images by a massive foreground cluster of galaxies acting like a cosmic zoom lens. Three images of the supernova were first found from archival data taken in 2016 by NASA's Hubble Space Telescope.
The multiple images are produced by the monster galaxy cluster's powerful gravity, which distorts and magnifies the light from the supernova far behind it, an effect called gravitational lensing. First predicted by Albert Einstein, this effect is similar to a glass lens bending light to magnify the image of a distant object.
The three lensed supernova images, seen as tiny dots captured in a single Hubble snapshot, represent light from the explosive aftermath. The dots vary in brightness and color, which signify three different phases of the fading blast as it cooled over time.
"This new discovery is the third example of a multiply imaged supernova for which we can actually measure the delay in arrival times," explained lead researcher Steve Rodney of the University of South Carolina in Columbia. "It is the most distant of the three, and the predicted delay is extraordinarily long. We will be able to come back and see the final arrival, which we predict will be in 2037, plus or minus a couple of years."
The light that Hubble captured from the cluster, MACS J0138.0-2155, took about four billion years to reach Earth. The light from Supernova Requiem needed an estimated 10 billion years for its journey, based on the distance of its host galaxy.
The team's prediction of the supernova's return appearance is based on computer models of the cluster, which describe the various paths the supernova light is taking through the maze of clumpy dark matter in the galactic grouping. Dark matter is an invisible material that comprises the bulk of the universe's matter and is the scaffolding upon which galaxies and galaxy clusters are built.
Each magnified image takes a different route through the cluster and arrives at Earth at a different time, due, in part, to differences in the length of the pathways the supernova light followed.
"Whenever some light passes near a very massive object, like a galaxy or galaxy cluster, the warping of space-time that Einstein's theory of general relativity tells us is present for any mass, delays the travel of light around that mass," Rodney said.
He compares the supernova's various light paths to several trains that leave a station at the same time, all traveling at the same speed and bound for the same location. Each train, however, takes a different route, and the distance for each route is not the same. Because the trains travel over different track lengths across different terrain, they do not arrive at their destination at the same time.
In addition, the lensed supernova image predicted to appear in 2037 lags behind the other images of the same supernova because its light travels directly through the middle of the cluster, where the densest amount of dark matter resides. The immense mass of the cluster bends the light, producing the longer time delay. "This is the last one to arrive because it's like the train that has to go deep down into a valley and climb back out again. That's the slowest kind of trip for light," Rodney explained.
The lensed supernova images were discovered in 2019 by Gabe Brammer, a study co-author at the Cosmic Dawn Center at the Niels Bohr Institute, University of Copenhagen, in Denmark. Brammer spotted the mirrored supernova images while analyzing distant galaxies magnified by massive foreground galaxy clusters as part of an ongoing Hubble program called REsolved QUIEscent Magnified Galaxies (REQUIEM).
He was comparing new REQUIEM data from 2019 with archival images taken in 2016 from a different Hubble science program. A tiny red object in the 2016 data caught his eye, which he initially thought was a far-flung galaxy. But it had disappeared in the 2019 images.
"But then, on further inspection of the 2016 data, I noticed there were actually three magnified objects, two red and a purple," he explained. "Each of the three objects was paired with a lensed image of a distant massive galaxy. Immediately it suggested to me that it was not a distant galaxy but actually a transient source in this system that had faded from view in the 2019 images like a light bulb that had been flicked off."
Brammer teamed up with Rodney to conduct a further analysis of the system. The lensed supernova images are arranged in an arc around the cluster's core. They appear as small dots near the smeared orange features that are thought to be the magnified snapshots of the supernova's host galaxy.
Study co-author Johan Richard of the University of Lyon in France produced a map of the amount of dark matter in the cluster, inferred from the lensing it produces. The map shows the predicted locations of lensed objects. This supernova is predicted to appear again in 2042, but it will be so faint that the research team thinks it will not be visible.
Catching the rerun of the explosive event will help astronomers measure the time delays between all four supernova images, which will offer clues to the type of warped-space terrain the exploded star's light had to cover. Armed with those measurements, researchers can fine-tune the models that map out the cluster's mass. Developing precise dark-matter maps of massive galaxy clusters is another way for astronomers to measure the universe's expansion rate and investigate the nature of dark energy, a mysterious form of energy that works against gravity and causes the cosmos to expand at a faster rate.
This time-delay method is valuable because it's a more direct way of measuring the universe's expansion rate, Rodney explained. "These long time delays are particularly valuable because you can get a good, precise measurement of that time delay if you are just patient and wait years, in this case more than a decade, for the final image to return," he said. "It is a completely independent path to calculate the universe's expansion rate. The real value in the future will be using a larger sample of these to improve the precision."
Spotting lensed images of supernovae will become increasingly common in the next 20 years with the launch of NASA's Nancy Grace Roman Space Telescope and the start of operations at the Vera C. Rubin Observatory. Both telescopes will observe large swaths of the sky, which will allow them to spot dozens more multiply imaged supernovae.
Future telescopes such as NASA's James Webb Space Telescope also could detect light from supernova Requiem at other epochs of the blast. The team's results will appear on September 13 in the journal Nature Astronomy.
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The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.
Media Contacts:
Claire Andreoli
NASA's Goddard Space Flight Center
Donna Weaver
Space Telescope Science Institute, Baltimore, Maryland
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
Science Contacts:
Steven A. Rodney
University of South Carolina, Columbia, South Carolina
Gabriel Brammer
Cosmic Dawn Center/Niels Bohr Institute/University of Copenhagen, Copenhagen, Denmark
Release:
NASA, ESA, University of South Carolina, Cosmic Dawn Center/Niels Bohr Institute/University of Copenhagen
JOURNAL
Nature Astronomy
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
A gravitationally lensed supernova with an observable two-decade time delay
ARTICLE PUBLICATION DATE
13-Sep-2021
Astronomers spot the same supernova three times — and predict a fourth sighting in 16 years
IMAGE: GRAVITY FROM THE MACS J0138 GALAXY CLUSTER CURVES SPACE SO MUCH THAT LIGHT FROM A GALAXY BEHIND IT IS BENT DOWN TOWARDS US IN SEVERAL DIFFERENT WAYS. TO THE LEFT IS A PICTURE OF THE CLUSTER FROM 2016 IN WHICH LIGHT FROM THE SAME EXPLODING STAR – A SUPERNOVA – IS SEEN IN THREE PLACES IN THE NIGHT SKY. TO THE RIGHT, IS THE SAME AREA IN 2019, WHERE THE SUPERNOVA IS NOW GONE. ASTRONOMERS FROM THE NIELS BOHR INSTITUTE HAVE CALCULATED THAT IT WILL REAPPEAR IN 2037 (CREDIT: S. RODNEY (U. OF S. CAROLINA), G. BRAMMER (COSMIC DAWN CENTER), J. DEPASQUALE (STSCI), P. LAURSEN (COSMIC DAWN CENTER)). view more
CREDIT: (CREDIT: S. RODNEY (U. OF S. CAROLINA), G. BRAMMER (COSMIC DAWN CENTER), J. DEPASQUALE (STSCI), P. LAURSEN (COSMIC DAWN CENTER)).
An enormous amount of gravity from a cluster of distant galaxies causes space to curve so much that light from them is bent and emanated our way from numerous directions. This “gravitational lensing” effect has allowed University of Copenhagen astronomers to observe the same exploding star in three different places in the heavens. They predict that a fourth image of the same explosion will appear in the sky by 2037. The study, which has just been published in the journal Nature Astronomy, provides a unique opportunity to explore not just the supernova itself, but the expansion of our universe.
One of the most fascinating aspects of Einstein's famed theory of relativity is that gravity is no longer described as a force, but as a "curvature" of space itself. The curvature of space caused by heavy objects does not just cause planets to spin around stars, but can also bend the orbit of light beams.
The heaviest of all structures in the universe — galaxy clusters made up of hundreds or thousands of galaxies — can bend light from distant galaxies behind them so much that they appear to be in a completely different place than they actually are.
But that’s not it: light can take several paths around a galaxy cluster, making it possible for us to get lucky and make two or more sightings of the same galaxy in different places in the sky using a powerful telescope.
Supernova déjà-vu
Some routes around a galaxy cluster are longer than others, and therefore take more time. The slower the route, the stronger the gravity; yet another astonishing consequence of relativity. This staggers the amount of time needed for light to reach us, and thereby the different images that we see.
This wondrous effect has allowed a team of astronomers at the Cosmic Dawn Center — a basic research center run by the Niels Bohr Institute at the University of Copenhagen and DTU Space at the Technical University of Denmark — along with their international partners, to observe a single galaxy in no less than four different places in the sky.
The observations were made using the infrared wavelength range of the Hubble Space Telescope.
By analyzing the Hubble data, researchers noted three bright light sources in a background galaxy that were evident in a previous set of observations from 2016, which disappeared when Hubble revisited the area in 2019. These three sources turned out to be several images of a single star whose life ended in a colossal explosion known as a supernova.
"A single star exploded 10 billion years ago, long before our own sun was formed. The flash of light from that explosion has just reached us," explains Associate Professor Gabriel Brammer of the Cosmic Dawn Center, who led the study with Professor Steven Rodney of the University of South Carolina.
The supernova, nicknamed "SN-Requiem," can be seen in three of the four "mirrored images" of the galaxy. Each image presents a different view of the explosive supernova’s development. In the final two images, it has not yet exploded. But, by examining how galaxies are distributed within the galaxy cluster and how these images are distorted by curved space, it is actually possible to calculate how “delayed” these images are.
This has allowed astronomers to make a remarkable prediction:
"The fourth image of the galaxy is roughly 21 years behind, which should allow us to see the supernova explode one more time, sometime around 2037," explains Gabriel Brammer.
Can teach us more about the universe
Should we get to witness the SN-Requiem explosion again in 2037, it will not only confirm our understanding of gravity, but also help to shed light on another cosmological riddle that has emerged in the last few years, namely the expansion of our universe.
We know that the universe is expanding, and that different methods allow us to measure by how fast. The problem is that the various measurement methods do not all produce the same result, even when measurement uncertainties are taken into account. Could our observational techniques be flawed, or — more interestingly — will we need to revise our understandings of fundamental physics and cosmology?
"Understanding the structure of the universe is going to be a top priority for the main earth-based observatories and international space organizations over the next decade. Studies planned for the future will cover much of the sky and are expected to reveal dozens or even hundreds of rare gravitational lenses with supernovae like SN Requiem," Brammer elaborates:
"Accurate measurements of delays from such sources provide unique and reliable determinations of cosmic expansion and can even help reveal the properties of dark matter and dark energy."
Dark matter and dark energy are the mysterious matter believed to make up 95% of our universe, whereas we can only see 5%. The perspectives of gravitational lenses are promising!
CAPTION
The light of a galaxy with an exploding star takes different paths around an intermediate galaxy cluster before it reaches us. Astronomers from the Cosmic Dawn Center, among others, have calculated that one route is about 21 light years longer than the other. As such, they predict that come 2037, we should be able to spot the supernova yet again. Click here for an animated version (illustration: Peter Laursen, Cosmic Dawn Center).
CREDIT
Peter Laursen, Cosmic Dawn Center).
JOURNAL
Nature
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE PUBLICATION DATE
13-Sep-2021
