Solving the mystery of the missing red supergiants

For decades, astronomers knew that red supergiants – massive stars in the final stage of life – should explode in supernovae. The math and the physics all said so. But in reality, these stars rarely seemed to explode. They were missing. And nobody knew why.

Thanks to a bit of cosmic luck and NASA’s James Webb Space Telescope (JWST), scientists have finally spotted the dying breath of one of the universe’s giants.

The end of this star’s life was veiled in clouds of dust, which might explain the mystery of the missing explosions.

The star that hid in plain sight

On June 29, 2025, a flash of light reached Earth from a galaxy called NGC 1637, about 40 million miles away. It was from a supernova – a star going out in a blaze of glory. Astronomers labeled it SN2025pht.

Using images taken before and after the explosion by Hubble and JWST, a research team tracked down the original star that caused the blast. It was a red supergiant, just as models had predicted. But this one wasn’t just red.

It was “the reddest, dustiest red supergiant that we’ve seen explode as a supernova,” said Aswin Suresh, a graduate student in physics and astronomy in the Weinberg College of Arts and Sciences at Northwestern.

Although the star shone about 100,000 times brighter than our sun, a thick shell of dust dimmed it by more than 100 times in visible light. That dust made it nearly impossible to spot until it exploded.

The mystery of missing red supergiants

Here’s the thing: massive stars should be easy to find. They’re huge, bright, and burn hot – basically, they are cosmic spotlights. But astronomers have always found fewer red supergiant explosions than expected. This new discovery helps explain why.

“For multiple decades, we have been trying to determine exactly what the explosions of red supergiant stars look like,” said Northwestern’s Charlie Kilpatrick, who led the study.

“These more massive supergiants are missing because they tend to be dustier,” he added. “Even I didn’t expect to see such an extreme example as SN2025pht.”

The star’s dusty veil wasn’t just thick – it was weird. “This tells us that the wind was very rich in carbon and less rich in oxygen, which also was somewhat surprising for a red supergiant of this mass,” Kilpatrick said.

A new eye on red supergiants

Until now, scientists couldn’t see stars like this because their dust blocked out the blue and visible light.

The Webb telescope’s ability to detect mid-infrared wavelengths changes the game. It can see through the dust. That’s how this team finally got a clear view of a red supergiant about to explode.

“We’ve been waiting for this to happen – for a supernova to explode in a galaxy that JWST had already observed,” Kilpatrick said.

“Only now, 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.”

This is JWST’s first direct detection of a supernova’s original star, or progenitor. It confirms that the red supergiants are still out there, doing exactly what scientists thought – they’ve just been hiding behind thick clouds of dust.

The stars still have secrets

The discovery also raises new questions. Why are some red supergiants dustier than others? Why was this star’s dust made of carbon? What other stars are lurking out there, waiting to explode?

Future telescopes, like NASA’s upcoming Nancy Grace Roman Space Telescope, may help answer those questions. It will be able to detect faint, dusty stars and watch them closely as they approach the ends of their lives.

“With the launch of JWST and upcoming Roman launch, this is an exciting time to study massive stars and supernova progenitors,” Kilpatrick said. “The quality of data and new findings we will make will exceed anything observed in the past 30 years.”

What makes this all so fascinating isn’t just the explosion – it’s the clarity. For the first time, astronomers could pull back the curtain on one of the Universe’s biggest disappearing acts.

The full study was published in The Astrophysical Journal Letters.

Image Credit: NASA, ESA, CSA, STScI, Charles Kilpatrick (Northwestern), Aswin Suresh (Northwestern)

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