JWST finds supernova ‘Hope’ that could finally resolve major astronomy controversy

Employing the JWST (James Webb Space Telescope), astronomers have captured a spectacular image of a faraway supernova in a galaxy that seems like it’s being stretched like warm taffy. But, the golden smear hiding this gravitationally lensed supernova, which has been given the nickname “supernova Hope,” isn’t just notable for its aesthetic value. The supernova, which exploded when the 13.8-billion-year-old cosmos was just around 3.5 billion years old, tells us something about a huge issue in cosmology called the “Hubble tension.”

The Hubble tension emanates from the fact that researchers can’t agree on the exact rate of expansion of the cosmos, dictated by the Hubble constant. Basically, the rate of expansion can be measured starting from the local (and therefore recent) cosmos, then going farther back in time — or, it can be calculated beginning from the distant (and therefore early) cosmos, then working your way up. The problem is both methods deliver values that are not in agreement with each other. This is where the James Web Space Telescope (JWST) comes in.

Gravitationally lensed supernovas in the early universe the JWST is observing could offer a third way of measuring the rate of expansion, potentially helping resolve this “Hubble trouble.” Supernova Hope is one such gravitationally lensed supernova. “The supernova was named ‘supernova Hope’ since it gives astronomers hope to better understand the universe’s changing expansion rate,” said Brenda Frye (study team leader and a University of Arizona researcher), in a NASA statement. “Gravitational lensing is important to this experiment. The lens, consisting of a cluster of galaxies that is situated between the supernova and us, bends the supernova’s light into multiple images,” said Frye. “This is similar to how a trifold vanity mirror presents three different images of a person sitting in front of it.”

Frye explained the effect was demonstrated right before the eyes of the team in the G165 JWST image, where the middle supernova image seemed flipped relative to the other two images.  “To achieve three images, the light traveled along three different paths. Since each path had a different length, and light traveled at the same speed, the supernova was imaged in this JWST observation at three different times during its explosion,” Frye continued. “In the trifold mirror analogy, a time delay ensued in which the right-hand mirror depicted a person lifting a comb, the left-hand mirror showed hair being combed, and the middle mirror displayed the person putting down the comb.”

This particular investigation of supernova Hope started when Brenda Frye and her global team of researchers found three curious points of light in a JWST image of a faraway, densely packed cluster of galaxies. Those points of light in the image were not visible when the Hubble Space Telescope imaged the very same cluster, known as PLCK G165.7+67.0 or, more simply, G165, way back in 2015. “It all started with one question by the team: ‘What are those three dots that weren’t there before? Could that be a supernova?'” said Frye. “Initial analyses confirmed that these dots corresponded to an exploding star, one with rare qualities.”