Webb Telescope unveils doomed star hidden in dust

Red dwarfs are very-low-mass stars. Image by NASA’s Goddard Space Flight Center. Chris Smith (USRA): Lead Producer – Public Domain

A new astronomical finding could help solve the mystery of the missing massive red ‘supergiants’. According to theory, massive red supergiant stars should cause most supernovae, yet they are rarely observed.

To help garner new information, Northwestern University scientists have used the James Webb Space Telescope (JWST) to make observations. The analysis of these shows an indication that these supernovae likely can occur yet they are hidden in dust.

Commenting on the study, lead scientist Charlie Kilpatrick states: “For multiple decades, we have been trying to determine exactly what the explosions of red supergiant stars look like.”

Now things are different: “With JWST, do we finally have the quality of data and infrared observations that allow us to say precisely the exact type of red supergiant that exploded and what its immediate environment looked like. We’ve been waiting for this to happen — for a supernova to explode in a galaxy that JWST had already observed. We combined Hubble and JWST data sets to completely characterize this star for the first time.”

Reddest, dustiest progenitor ever observed

Using the All-Sky Automated Survey of Supernovae, astronomers first detected the supernova, dubbed SN2025pht, on June 29, 2025. Its light had travelled from a nearby galaxy called NGC 1637, located 40 million light-years away from Earth.

By comparing Hubble and JWST images of NGC 1637 from before and after the star’s explosion, the researchers found SN2025pht’s progenitor star. It was immediately striking — extremely bright and incredibly red.

Although the star shined about 100,000 times brighter than our sun, surrounding dust obscured much of this light. The dusty veil was so thick, in fact, that the star appeared more than 100 times dimmer in visible light than it would appear without the dust. Because dust blocked out shorter, bluer wavelengths of light, the star also appeared surprisingly red.

Massive stars in the late stages of their lives, red supergiants are among the largest stars in the universe. When their cores collapse, they explode as Type II supernovae, leaving behind either a neutron star or black hole. The most familiar example of a red supergiant is Betelguese, the bright reddish star in the shoulder of the constellation Orion.

Clues hidden in dust

The deluge of dust could help explain why astronomers have struggled to find red supergiant progenitors. Most massive stars that explode as supernovae are the brightest and most luminous objects in the sky. So, theoretically, they should be easy to spot before they explode.

Astronomers posit that the most massive aging stars also might be the dustiest. These thick cloaks of dust might dim the stars’ light to the point of utter undetectability. The new JWST observations support this hypothesis.

In addition to the presence of dust itself, the dust’s composition was also surprising. While red supergiants tend to produce oxygen-rich, silicate dust, this star’s dust appeared rich with carbon. This suggests that powerful convection in the star’s final years may have dredged up carbon from deep inside, enriching its surface and altering the type of dust it produced.

A new era for exploding stars

The new study marks the first time astronomers have used JWST to directly identify a supernova progenitor star, opening the door to many more discoveries. By capturing light across the near- and mid-infrared spectrum, JWST can reveal hidden stars and provide missing pieces for how the most massive stars live and die.

The team now is searching for similar red supergiants that may explode as supernovae in the future. Observations by NASA’s upcoming Nancy Grace Roman Space Telescope may help this search. Roman will have the resolution, sensitivity and infrared wavelength coverage to see these stars and potentially witness their variability as they expel out large quantities of dust near the end of their lives.

The research appears in The Astrophysical Journal Letters. It is titled: “The Type II SN 2025pht in NGC 1637: A red supergiant with carbon-rich circumstellar dust as the first JWST detection of a supernova progenitor star.”