Imagine surveying a large portion of the sky that constitutes an area no larger than a grain of rice held at arm’s length and detonating star deaths that,
EXCEPTION took place billions of years ago. Working in this way, NASA’s James Webb Space Telescope made a treasure trove of early supernovae discoveries, further taking the understanding of the cosmos to its very young stage.
NASA’s JWST has detected a record 80 new supernovae—roughly 10 times as many as were previously known in the early universe. Some of the stellar detonations went off when the cosmos was just about 1.8 billion years old. For comparison, today it is about 13.8 billion years old. The finds are opening up new routes for astronomical research into how the cosmos evolved in its formative years.
This was best summarized by Christa DeCoursey, a third-year graduate student at the Steward Observatory and the University of Arizona in Tucson. She said, “Webb is a supernova discovery machine. The two most exciting results from our survey are the great number of detections plus the huge distances to these supernovae.”
They turn off when a star has used up all of its nuclear fuel and collapses under its own gravity—the event that produces many black holes and neutron stars. Helping to back up these great discoveries is the program called JADES, standing for JWST Advanced Deep Extragalactic Survey. It detected the ancient supernovas through an effect called cosmological redshift. That is what happens, however, when the universe is expanding, or rather, the light from these distant galaxies gets stretched into longer wavelengths, shifting it towards the red end of the spectrum.
“Because Webb is so sensitive, it’s finding supernovae and other transients almost everywhere it’s pointed,” said Eiichi Egami, a research professor at the University of Arizona in Tucson. This ability of JWST has thereby been uniquely useful for discovering ancient stellar explosions.
One of these newly discovered supernovae exploded when the Universe was only 1.8 billion years old, making it both the oldest and farthest supernova ever found. That’s a type of supernova—the kind of supernova that astrophysicists think is special because its brightness is reproducibly predictable. It’s with Type Ia supernovas functioning as “standard candles” that astrophysicists measure cosmic distances and the universe’s expansion rate. Of equal importance for them is an understanding about whether their intrinsic brightness changes with redshift; this impacts how dependable they are in measuring the expansion of the universe.
“This is really our first sample of what the high-redshift universe looks like for transient science,” said Justin Pierel, a NASA Einstein Fellow at the Space Telescope Science Institute in Baltimore, Maryland. “We are trying to understand whether distant supernovae are fundamentally different from or very much like what we see in the nearby universe.”
Astronomers in the past could only dream of studying such cosmic phenomena. Before JWST, there were only a few supernovae known to have the redshift value indicating that they have lived since when the universe was younger than about 3.3 billion years old. It is precisely this magnificent capability that JWST now exposes supernovas from when the universe was less than 2 billion years old, giving scientists a window to an early universe vastly different from the one we know today.
We’re essentially opening a new window on the transient universe,” said Matthew Siebert, who leads the spectroscopic analysis of the JADES supernovas. “Historically, whenever we’ve done that, we’ve found extremely exciting things — things that we didn’t expect.”
Not merely an inventory of supernovae in a catalog, these come with crucial data delivered to help scientists understand how the universe has come to look the way it does today. For example, comparing ancient supernovae with those in the local universe, astrophysicists would learn about star-formation mechanisms and how they exploded at these early times. Understanding this kind is one of the pillars of the history of the Cosmos from the formation of the very first stars and first galaxies to the structure seen today.
For the future, scientists are optimistic that JWST will relate more about the universe’s earliest epochs. Scientists look keenly further back in time, appreciating the era when the very first generation of stars died. This kind of discovery could transform our understanding of cosmology and star life cycles.
Their results were presented at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin, covering how great an extent these ancient supernovas challenge and enrich previous knowledge about cosmic history. The first glimpse with JWST at stellar phenomena is a success signal in astronomical research. More such pathbreaking discoveries have yet to come.
So next time you gaze out upon a star-studded night sky, remember that things like JWST aren’t taking snapshots of really distant stars but billions of years in the past for some of the most dramatic and enlightening moments in universal history.
