Supernovae May Have Shaped the Early Universe, Webb Finds – Sky & Telescope

Brilliant, ephemeral, and deadly, supernovae are a powerful force in the cosmos. Through their deaths, they’ve enriched the universe with new elements, shaping the next generations of stars. Now, astronomers at the 245^th meeting of the American Astronomical Society present new observations from the James Webb Space Telescope, reporting the discovery of a supernova hailing from the young universe and revealing how these stellar explosions may provide young galaxies with the material to form stars.

An Early Supernova

Webb, with its increased sensitivity and infrared detector, is the first telescope with the capacity to find a supernova from the first generation of stars that formed after the Big Bang. “These stars were considerably different than the stars today,” said team lead David Coulter (Space Telescope Science Institute), who presented the results at the AAS meeting. “They were massive, they were hot, and they had truly gargantuan explosions.”

Coulter led a team in using the JWST Advanced Deep Extragalactic Survey (JADES) to search for supernovae in the first billions of years after the Big Bang. To find these events, the team examined the same field of sky in the fall of 2022 and then again in 2023, subtracting the images from each other to highlight new features that had appeared.

They found dozens of transients in these tiny regions of sky — each one a fraction of a pinky nail on the sky. Subsequent observations revealed that one bright transient was an early supernova, occurring when the universe was less than 2 billion years old.

Analyzing the Webb data, the team was able to classify the distant transient as a core-collapse supernova, which happens when a massive star runs out of fuel and collapses under the weight of its own gravity.

The team also determined that the original star might have been 20 times the Sun’s mass, created in a pristine environment in which elements heavier than hydrogen and helium amounted to only a third of today’s heavy-element fraction.

“Although supernovae are rare, they play a major role in the evolution of the universe, spreading heavy elements throughout the cosmos and shaping how galaxies form and change,” says Saurabh Jha (Rutgers University), who was not involved with the new study.

As stars evolve, first burning hydrogen into helium, then helium into heavier elements, they produce other crucial elements on the periodic table — such as the carbon, oxygen, and nitrogen atoms that are vital to life. Supernovae explosively distribute these materials into interstellar space, where they are taken up into the next generation of stars and planets.

“We are really interested to learn whether these supernovae at early times were different in any way than the ones we see in the nearby Universe,” Jha says. “That would tell us how the conditions for stars to form, live, and die changed over cosmic time.”

Rapid Dust Factories

In another Webb-related result, Melissa Shahbandeh (Space Telescope Science Institute) reported at the AAS meeting that certain core-collapse supernovae may have been major dust producers in the young universe.

Astronomers previously thought that asymptotic giant branch (AGB) stars, cool luminous stars that power strong winds, produced most of the dust in the early universe. However, JWST observations found that early galaxies had a lot more dust than could be accounted for by AGB stars, which take millions of years to shed their outer layers and enrich their environment with dust.

Core-collapse supernovae are an appealing alternative, since they come from shorter-lived stars. “When we’re talking about the very first hundreds of millions of years of the universe, core-collapse supernovae are ‘first out of the gate’ and should dominate dust production,” said Chris Burns (Carnegie Observatories), who was not involved in the study. But it remained unclear how the dust could survive the supernova blasts.

Supporting this idea, Shahbandeh led a team that looked at a nearby supernova (SN 2005ip) in which the cast-off outer layers plow into surrounding gas, known as a Type IIn or interacting supernova. These explosions often remain bright for years. Comparing data from the Spitzer Space Telescope, taken three years after the explosion, with recent JWST data taken 15 years later, the team found that the supernova remnant was full of dust.

The Webb spectrum reveals cold silicate dust is still forming in the aftermath of the supernova — about 0.1 solar masses of it. “What this is telling us is that this supernova not only was hosting a lot of dust three years post-explosion, but it kept forming dust,” Shahbandeh said.

The team suspects that the continued dust production has to do with a cold, dense shell of dust that formed around the interacting supernova as it began to cool down. The shell protects the dust within from being destroyed by shock waves that are still traveling outward through the surrounding gas.

Shahbandeh thinks this type of supernovae could be rapid dust factories: “[They] could be the main contributors to the significant amount of dust observed in the early universe.”

“Type IIn supernovae are relatively rare in the nearby universe but could have been more common early on,” Jha says, “so I find the argument that they could contribute substantially to dust formation in the early universe quite plausible.”

As Webb enables astronomers to peer deeper into cosmic time, it has opened up a new window in supernova science. “JWST is leading the way to get to earlier and earlier times in the universe to find these truly massive stars and their explosions,” Coulter says. Both results have shed light on the role of early supernovae in the young universe.

In addition to Webb, ground-based telescopes such as the near-complete Vera Rubin Observatory in Chile are aiming to discover ever more supernovae in extended sky surveys, enabling astronomers to better understand how the blasts help shape galaxy evolution and star formation. Ground-based and space telescopes will continue to push into this more distant frontier, illuminating the universe’s first supernovae for the first time.