James Webb Telescope Finds Earliest Supernova Ever: GRB 250314A (2025)

JWST Discovery Today - James Webb Telescope Finds Earliest Supernova Ever: GRB 250314A (2025)

JWST NIRCam image of GRB 250314A, the earliest supernova ever seen at 730 million years after Big Bang, with host galaxy inset

James Webb Space Telescope captures GRB 250314A – the earliest supernova ever detected, exploding when the Universe was only 730 million years old. The faint red dot (zoomed inset) is the supernova inside its distant host galaxy at redshift z≈7.3. Credit: NASA, ESA, CSA, STScI, Andrew Levan (Radboud University); Image Processing: Alyssa Pagan (STScI)

Updated on: December 09, 2025 | By: Jameswebb Discovery Editorial Team

James Webb Telescope Detects GRB 250314A: Earliest Supernova Ever Seen – Exploding Star from 730 Million Years After Big Bang (December 2025)

NASA's James Webb Space Telescope (JWST) has shattered records once again, confirming the earliest supernova ever observed – a cataclysmic stellar explosion that lit up the cosmos when the Universe was just 730 million years old. Linked to the gamma-ray burst GRB 250314A, this distant blast offers a stunning glimpse into the Universe's infancy, revealing a massive star's death throes during the Era of Reionization.JWST's Near-Infrared Camera (NIRCam) captured high-resolution images on July 1, 2025, pinpointing the supernova's faint red glow and its elusive host galaxy – a breakthrough that previous telescopes couldn't achieve. "Only Webb could directly show that this light is from a supernova – a collapsing massive star," said lead researcher Andrew Levan from Radboud University and the University of Warwick.This discovery not only breaks JWST's own previous record (a supernova at 1.8 billion years old) but also hints at surprisingly mature stellar processes in the young Universe.

The Explosive Birth of GRB 250314A: A Cosmic Flash from the Dawn of Time

Imagine a massive star – dozens of times the Sun's size – racing through its brief, furious life in a galaxy barely formed. Its core collapses, unleashing a supernova that outshines billions of stars. But the real fireworks? Ultra-relativistic jets piercing the star's envelope, beaming gamma rays across the cosmos.That's GRB 250314A: a long-duration gamma-ray burst (LGRB) lasting ~10 seconds, detected on March 14, 2025, by the Franco-Chinese SVOM (Space-based Multi-band Astronomical Variable Objects Monitor) mission. SVOM, launched in 2024, is purpose-built for such fleeting events.

Rapid response: Within 1.5 hours, NASA's Neil Gehrels Swift Observatory localized the X-ray afterglow.
Distance clue: 11 hours later, the Nordic Optical Telescope in the Canary Islands spotted an infrared afterglow, signaling extreme distance.
Redshift confirmation: Four hours after that, ESO's Very Large Telescope (VLT) in Chile pegged the redshift at z ≈ 7.3 – light traveled ~13.07 billion years, from an era just 5% into cosmic history.

"There are only a handful of gamma-ray bursts in the last 50 years from the first billion years of the Universe," Levan noted. "This one is very rare and very exciting."Unlike short GRBs (from neutron star mergers), LGRBs like this trace massive star deaths – hypernovae that carve black holes and seed heavy elements.

JWST's Nimble Follow-Up: Capturing a Slow-Motion Supernova

Supernovae brighten over weeks, but cosmic expansion stretches their light and timelines. At z=7.3, events unfold ~8 times slower due to time dilation. The underlying supernova peaked months after the GRB.JWST's Director's Discretionary Time (DDT) program #9296 sprang into action July 1 – 3.5 months post-burst – using NIRCam filters (F150W, F200W, F277W, F356W, F444W) to catch the glow at peak.Key revelations:

Supernova confirmation: A faint red point source, brighter than expected, matching a collapsing massive star's signature.
Host galaxy detection: Blended into pixels as a "reddened smudge," but visible – similar to other z~7 galaxies, with young, blue stars and low metallicity.
No surprises?: Shockingly, its light curve and spectrum mimic nearby supernovae like SN 1998bw (linked to GRB 980425), despite early Universe conditions.

"We went in with open minds," said co-author Nial Tanvir (University of Leicester). "And lo and behold, Webb showed this supernova looks exactly like modern ones."Early stars were metal-poor, more massive, and short-lived, amid the foggy Era of Reionization (when UV light ionized intergalactic gas). Yet GRB 250314A's familiarity suggests stellar evolution stabilized faster than thought.

Why This Earliest Supernova Matters: Peering into Cosmic Reionization

This isn't just a "first" – it's a window into the Universe's toddler years:

Stellar forensics: Confirms LGRBs as probes of Population III stars (first generation, metal-free).
Element factories: Supernovae forge iron, oxygen, and more – seeding galaxies for future life.
Reionization clues: The host's faint glow hints at how early UV bursts cleared cosmic fog.
GRB rarity: Only ~5 such ancient GRBs known; JWST's sensitivity unlocks more.

"Webb provided the rapid and sensitive follow-up we needed," said Benjamin Schneider (Laboratoire d'Astrophysique de Marseille). Future plans: Use GRB afterglows as "fingerprints" to map distant galaxies. The host appears compact and star-forming, blending into a few pixels – a testament to JWST's infrared edge over Hubble.