Free Astronomy Magazine September-October 2024

29 SEPTEMBER-OCTOBER 2024 in the early universe than were pre- viously known. A few of the new- found exploding stars are the most distant examples of their type, in- cluding those used to measure the universe’s expansion rate. “Webb is a supernova discovery ma- chine,” said Christa DeCoursey, a third-year graduate student at the Steward Observatory and the Uni- versity of Arizona in Tucson. “The sheer number of detections plus the great distances to these supernovae T he JADES Deep Field uses observations taken by NASA’s James Webb Space Telescope (JWST) as part of the JADES (JWST Advanced Deep Extragalactic Survey) program. A team of astronomers studying JADES data identified about 80 objects (circled in green) that changed in brightness over time. Most of these objects, known as transients, are the result of exploding stars or supernovae. Prior to this survey, only a handful of supernovae had been found above a red- shift of 2, which corresponds to when the universe was only 3.3 billion years old — just 25% of its current age. The JADES sample contains many supernovae that exploded even further in the past, when the universe was less than 2 billion years old. It includes the farthest one ever spectroscopically confirmed, at a red- shift of 3.6. Its progenitor star exploded when the universe was only 1.8 billion years old. [NASA, ESA, CSA, STScI, JADES Collaboration] are the two most exciting outcomes from our survey.” DeCoursey presented these findings in a press conference at the 244 th meeting of the American Astronom- ical Society in Madison, Wisconsin. To make these discoveries, the team analyzed imaging data obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES) pro- gram. Webb is ideal for finding ex- tremely distant supernovae because their light is stretched into longer wavelengths — a phenomenon known as cosmological redshift. Prior to Webb’s launch, only a hand- ful of supernovae had been found above a redshift of 2, which corre- sponds to when the universe was only 3.3 billion years old — just 25% of its current age. The JADES sam- ple contains many supernovae that exploded even further in the past, when the universe was less than 2 billion years old. Previously, researchers used NASA’s Hubble Space Telescope to view su- pernovae from when the universe was in the “young adult” stage. With JADES, scientists are seeing su- pernovae when the universe was in its “teens” or “pre-teens.” In the fu- ture, they hope to look back to the “toddler” or “infant” phase of the universe. To discover the supernovae, the team compared multiple images taken up to one year apart and looked for sources that disappeared or appeared in those images. These objects that vary in observed bright- ness over time are called transients, and supernovae are a type of tran- sient. In all, the JADES Transient Sur- vey Sample team uncovered about 80 supernovae in a patch of sky only about the thickness of a grain of rice held at arm’s length. “This is really our first sample of what the high-redshift universe looks like for transient science,” said teammate Justin Pierel, a NASA Ein- stein Fellow at the Space Telescope Science Institute (STScI) in Balti- more, Maryland. “We are trying to identify whether distant super- novae are fundamentally different from or very much like what we see in the nearby universe.” Pierel and other STScI researchers provided expert analysis to deter- mine which transients were actually supernovae and which were not, because often they looked very sim- ilar. The team identified a number of high-redshift supernovae, including the farthest one ever spectroscopi- cally confirmed, at a redshift of 3.6. Its progenitor star exploded when the universe was only 1.8 billion years old. It is a so-called core-col- lapse supernova, an explosion of a massive star. Of particular interest to astrophysi- cists are Type Ia supernovae. These exploding stars are so predictably bright that they are used to meas-