Free Astronomy Magazine September-October 2024

30 SEPTEMBER-OCTOBER 2024 ASTRO PUBLISHING T his mosaic displays three of about 80 transients, or objects of changing bright- ness, identified in data from the JADES (JWST Advanced Deep Extragalactic Survey) pro- gram. Most of the transients are the result of exploding stars or supernovae. By comparing images taken in 2022 and 2023, astronomers could locate su- pernovae that, from our per- spective, re- cently exploded (like the examples shown in the first two columns), or supernovae that had already exploded and whose light was fading away (third column). The age of each supernova can be determined from its redshift (designated by ‘z’). The light of the most distant supernova, at a redshift of 3.8, originated when the universe was only 1.7 billion years old. A redshift of 2.845 corresponds to a time 2.3 billion years after the big bang. The closest example, at a redshift of 0.655, shows light that left its galaxy about 6 billion years ago, when the universe was just over half its current age. [NASA, ESA, CSA, STScI, Christa DeCoursey (University of Arizona), JADES Collaboration] verse will help astrophysicists un- derstand star formation and super- nova explosion mechanisms at these early times. “We’re essentially opening a new window on the transient universe,” said STScI Fellow Matthew Siebert, who is leading the spectroscopic analysis of the JADES supernovae. “Historically, whenever we’ve done that, we’ve found extremely excit- ing things — things that we didn’t expect.” “Because Webb is so sensitive, it’s finding supernovae and other transients almost everywhere it’s pointed,” said JADES team member Eiichi Egami, a research professor at the University of Arizona in Tucson. “This is the first significant step to- ward more extensive surveys of su- pernovae with Webb.” Pierel analyzed this Type Ia super- nova found at redshift 2.9 to deter- mine if its intrinsic brightness was different than expected. While this is just the first such object, the re- sults indicate no evidence that Type Ia brightness changes with redshift. More data is needed, but for now, Type Ia supernova-based theories about the universe’s expansion rate and its ultimate fate remain intact. Pierel also presented his findings at the 244 th meeting of the American Astronomical Society. The early universe was a very differ- ent place with extreme environ- ments. Scientists expect to see an- cient supernovae that come from stars that contain far fewer heavy chemical elements than stars like our Sun. Comparing these super- novae with those in the local uni- ure far-off cosmic distances and help scientists to calculate the uni- verse’s expansion rate. The team identified at least one Type Ia super- nova at a redshift of 2.9. The light from this explosion began traveling to us 11.5 billion years ago when the universe was just 2.3 billion years old. The previous distance record for a spectroscopically con- firmed Type Ia supernova was a red- shift of 1.95, when the universe was 3.4 billion years old. Scientists are eager to analyze Type Ia supernovae at high redshifts to see if they all have the same intrinsic brightness, regardless of distance. This is critically important, because if their brightness varies with red- shift, they would not be reliable markers for measuring the expan- sion rate of the universe. !