An international team of astronomers has detected an unusual supernova that is curiously lacking in metals, an observation that offers vital clues about the early galaxy.
The highly irregular cosmic explosion is only the second of its kind witnessed by astronomers. The team’s work creates a baseline for observing stars in these young, low-metal galaxies, which were too dim to see before the launch of the James Webb Space Telescope (JWST) in 2021.
An Astronomical Anomaly
The unusual supernova, formally designated 2023ufx, was born when a red supergiant star’s core collapsed on itself, generating a massive stellar explosion.
Occurring on the edges of a nearby dwarf galaxy, the resulting supernova and the surrounding galaxy were unusually poor in metals, lacking appreciable levels of anything heavier than hydrogen and helium.
What is most intriguing to astronomers, however, is what may be revealed about the early universe when studying such unique supernovae.
An Early Universe Reflected
The early universe did not have the same prevalence of metals as it does today, given that they had not yet had time to form that early in cosmic history. Since metals significantly impact a star’s entire life span from formation to death, these low-metal stars provide insight into how the process worked in an early low-metal universe. Metals also impact how long the explosions are visible and how many nuclear reactions they have. A lack of metals also increases the likelihood of a low-mass star becoming a black hole, potentially without even becoming a supernova first.
“If you’re someone who wants to predict how the Milky Way came to be, you want to have a good idea of how the first exploding stars seeded the next generation,” said Tucker in a statement. “Understanding that gives scientists a great example of how those first objects affected their surroundings.”
Further compounding the supernova’s similarity to the early universe is its location inside a dwarf galaxy, which resembles the conditions expected in the early universe. While the early universe was metal-poor, older galaxies like Earth’s Milky Way have experienced many star explosions, increasing those galaxy’s metal content and brilliance.
JWST Provides New Views
Due to their lack of lasting brilliance, low-metal supernovas are exceedingly difficult to spot from Earth. Beyond just their dimness, they remain visible for a much shorter duration than metallic supernovas.
The 2023ufx supernova stayed bright for only roughly 20 days, compared to the 100 days generally expected of a metal-rich supernova. NASA’s James Webb Space Telescope made these faint events visible for the first time, capturing them within its constrained visibility window.
“There are not that many metal-poor locations in the nearby universe and before JWST, it was difficult to find them,” said Tucker.
High-Speed Early Stars
The explosions emitted vast amounts of high-speed ejecta, indicating that the stars were spinning at an enormous rate of speed as they exploded. After viewing the supernova, the team came to believe that metal-poor stars of the early universe were often spinning at a tremendous rate of speed. The supernova likely had weak streams of particles called stellar winds coming from the star, which led to its development and finally releasing enormous energy.
“If you’re someone who wants to predict how galaxies form and evolve, the first thing you want is a good idea of how the first exploding stars influenced their local area,” said Tucker.
Future Work
Observing such a rare event laid the necessary groundwork against which to compare future observations. Much research remains on these rare supernovas as astronomers await future events, providing more data. Questions include whether the supernova was larger in the past and whether a binary star absorbed many elements.
“We’re so early in the JWST era that we’re still finding so many things we don’t understand about galaxies,” said Tucker. “The long-term hope is that this study acts as a benchmark for similar discoveries.”
The paper “The Extremely Metal-poor SN 2023ufx: A Local Analog to High-redshift Type II Supernovae” appeared on November 21, 2024, in The Astrophysical Journal.
Ryan Whalen covers science and technology for The Debrief. He holds a BA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.