Visible to Webb, not to Hubble: Star before supernova could solve a mystery
The James Webb Space Telescope has only been researching for three and a half years, but it has already imaged a giant star that has since exploded.
Image of a galaxy, with enlargements showing that the star was visible to Webb but not to Hubble
(Image: NASA, ESA, CSA, STScI, C. Kilpatrick (Northwestern), A. Suresh (Northwestern); Image Processing: J. DePasquale (STScI))
For the first time, a research group has succeeded in identifying a star in old images from the James Webb Space Telescope that later exploded as a supernova. It is a red supergiant that was detectable at the edge of the galaxy NGC 1637, only about 40 million light-years away, until it exploded on June 29, 2025. The star was subsequently identified in archival images from the space telescope, which has only been active for a few years, and turned out to be “surprisingly red,” the research group writes. This suggests that it was surrounded by dust before its end, which filtered out the blue wavelengths. This finding could now help solve a puzzle in astronomy.
Surprisingly well hidden
The progenitor star was discovered in images taken by the space telescope in 2024, the team writes. And the fact that it was so unexpectedly red in them could help clarify the “case of the missing red supergiants.” This refers to the fact that one would actually expect the most massive stars to be the brightest before their end in a supernova. Therefore, they should be easily found in archival images afterward. The star, which has now ended in supernova 2025pht, suggests that such celestial bodies are surrounded by dense dust in this phase of their development, which effectively hides them. The star is not visible in an archival image from the Hubble Space Telescope, which researches in a different spectrum.
Videos by heise
It was also for this major question that scientists were waiting for a supernova like 2025pht, writes study leader Charlie Kilpatrick of Northwestern University in Illinois. It was particularly helpful that the James Webb Space Telescope also observed the progenitor star in the mid-infrared spectrum, as this allowed the composition of the dust to be analyzed. It was surprisingly carbon-rich, whereas silicates were expected. One can only speculate, but the carbon could have been ejected from the interior of the star shortly before the explosion. The research paper on the finding has been published in the journal “The Astrophysical Journal Letters.”
The James Webb Space Telescope was launched on December 25, 2021, in such an ideal way that the saved propellant has enabled a doubling of the mission duration to 20 years. In early July 2022, the instrument began its research work and has since been responsible for important and sometimes groundbreaking discoveries with great regularity. A series of its observations are challenging our assumptions about the early universe. For example, the instrument has detected tiny, extremely bright, and strikingly red points of light that may not be surprisingly mature galaxies, but active black holes. Two years ago, an unexpectedly early collision of two exceptionally massive galaxies was also found.
(mho)
