Tucson Standard

Peering deeply into the cosmos, NASA's James Webb Space Telescope (JWST) is providing scientists their first detailed glimpse of supernovas from a time when the universe was young. A team using JWST data has identified 10 times more supernovas in the early universe than were previously known. Some of these newfound exploding stars are the most distant examples of their type, including those used to measure the universe's expansion rate.

"Webb is a supernova discovery machine," said Christa DeCoursey, a University of Arizona graduate student in the Department of Astronomy and Steward Observatory who led the research. "The sheer number of detections, plus the great distances to these supernovae, are the two most exciting outcomes from our survey."

DeCoursey presented the findings this week at a press conference at the 244th meeting of the American Astronomical Society in Madison, Wisconsin.

To make these discoveries, the team analyzed imaging data obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. Webb is ideal for finding extremely distant supernovas because their light is stretched into longer wavelengths by the expansion of the universe, a phenomenon known as cosmological redshift. The more distant the supernova, the more dramatic its redshift.

Prior to JWST's launch, only a handful of supernovas had been found above a redshift of two, which corresponds to when the universe was only 3.3 billion years old—just 25% of its current age.

Previously, researchers used NASA's Hubble Space Telescope to view supernovas from when "the universe was like a young adult," according to DeCoursey's team. With JADES, scientists are seeing supernovas when "the universe was in its teenage years." In future studies, they hope to look back to even younger phases of cosmic history.

To discover these supernovas, researchers compared multiple images taken up to one year apart and looked for sources that disappeared or appeared over time—objects known as transients. Supernovas are one type of transient event. The JADES Transient Survey Sample team uncovered about 80 supernovas in a patch of sky roughly equivalent to "the thickness of a grain of rice held at arm's length."

"This is really our first sample of what high-redshift transient science looks like," said teammate Justin Pierel, a NASA Einstein Fellow at Baltimore’s Space Telescope Science Institute (STScI). "We are trying to identify whether distant supernovae are fundamentally different from or very much like what we see in our nearby universe."

Pierel and other STScI researchers provided expert analysis to determine which transients were actually supernovas and which were not due to often similar appearances.

The team identified several high-redshift supernovas including one at redshift 3.6—the farthest ever confirmed—which exploded when the universe was only 1.8 billion years old and is classified as a core-collapse supernova.

The early universe featured extreme environments with ancient stars containing fewer heavy chemical elements than stars today such as our sun. Comparing ancient and local-universe supernovas will help astrophysicists understand star formation and explosion mechanisms during early cosmic times.

"We're essentially opening a new window on transient science," said Matthew Siebert from STScI who leads spectroscopic analysis for JADES' findings on these events. "Historically whenever we've done that we've found extremely exciting things—things we didn't expect."

"Because Webb is so sensitive it's finding transients almost everywhere it's pointed," noted Eiichi Egami—a UArizona research professor involved with JADES work on JWST data interpretation—as he emphasized this marks an important step towards extensive surveys using JWST capabilities.