Supernovae appear as ordinary stars

When viewed from Earth, supernovae can appear like ordinary stars. However, they are the extremely powerful explosion of a dying star.

Supernova light lasts weeks or months

Generally, the light emitted during the explosion remains visible for a few weeks, or even a few months for the most massive ones, and it is necessary to be quick to capture the maximum data before the event becomes invisible.

New study detects early supernova

In a study not yet peer-reviewed, published on September 29 on the arXiv server and noted by the site Phys.org, a team led by astronomer Ming-Yang Zhuang, from the University of Illinois at Urbana-Champaign, reports a probable supernova detected only four to ten days after the explosion.

Signal is extremely distant

The signal is named AT 2026abck and is extremely far in the universe, with a redshift (the shift of its light toward the red, which indicates its distance) of 5.017, which means that when the light was emitted, the universe was slightly more than one billion years old.

James Webb Telescope detects rare event

The James Webb Telescope passes and repasses This type of discovery so far back in time is quite rare. Only 200 supernovae have been discovered at distances equivalent to a redshift of 4.

Gravitational lensing not involved

Gravitational lensing phenomena, which have a magnifying effect, are particularly useful for detecting these very luminous but also extremely distant and therefore difficult-to-find sources. In this case, no gravitational lensing has amplified the signal.

JWST's capabilities help detection

Everything relies on the capabilities of the James Webb Space Telescope, capable of "seeing" very far into the infrared and detecting luminous sources, even weak ones. The NEXUS observation program uses the JWST to revisit the same area of the sky every two months and detect transient signals, such as supernovae.

Signal detected after 71 days

The telescope thus detected a light that was absent during its previous passage on May 28, 2026, 71 days earlier. Once the signal was under their eyes, scientists tried to characterize it, and based on its diameter 92 times greater than the distance between Earth and the Sun, and its temperature of about 17,000 kelvins (nearly 16,700 °C), they concluded that the explosion had occurred only four to ten days ago.

Uncertainty about the type of supernova

But is it really a supernova? On this point, the study authors acknowledge a slight uncertainty because the light seems to correspond to a Type II supernova, and thus the end of life of an extremely massive star, but it is several thousand degrees too hot for the model to work perfectly.

New observations needed

New observations from the JWST will have to help determine the exact nature of the phenomenon. Regardless, supernovae at such distances provide information about the nature of this distant universe.

Distant universe had different conditions

At that time, galaxies were younger than what we can see around the Milky Way. The stars also had a different composition, with much fewer heavier elements than helium (those that astronomers call all "metals"). Their formation rate was also particularly intense.

Observing distant stars and galaxies

All this indicates an environment very exotic compared to what we know closer to us. But at such a distance, data is lacking. A very bright supernova therefore offers the opportunity to directly observe these stars and their galaxies.