# JWST spectroscopy identifies lensed Type IIb supernova Ares at z=1.276 behind MACS J0308.9+2645

- Published: 2026-11-15 14:06 UTC
- Section: Sky & Space › Astronomy
- Tags: SN Ares, lensed supernova, Type IIb supernova, JWST NIRSpec spectroscopy, MACS J0308.9+2645, galaxy cluster lens model, redshift 1.276, time delay of images, stripped-envelope supernova
- URL: https://realtech.media/news/rt-836e088710796bb4a347c24e_jwst_spectroscopy_identifies/

**Astronomers report SN Ares, a lensed Type IIb supernova observed by JWST; the cluster lens model predicts two more images of it in about 70 years or more.**

![JWST spectroscopy identifies lensed Type IIb supernova Ares at z=1.276 behind MACS J0308.9+2645](https://realtech.media/media/2026/11/d427df447e378872.webp)
*Interesting Engineering*

Astronomers have reported the discovery of supernova Ares, a strongly lensed explosion at spectroscopic redshift z = 1.276 ± 0.002, in a paper posted on arXiv (Cornell University) [1]. The supernova lies in a massive, triply imaged host galaxy behind the galaxy cluster MACS J0308.9+2645 [1]. According to Interesting Engineering, the near-infrared images were taken by the James Webb Space Telescope (JWST) in August 2025, and the light left the star about 8.8 billion years ago.

Gravitational lensing by the cluster splits the light of the background source into several images, and each image travels a path of a different length. This is why the same explosion can be observed more than once, at different times.

## Spectroscopy and classification

Spectra from JWST/NIRSpec cover the rest-frame optical to near-infrared range. They show helium features at 5876, 7065 and 10830 Å, as well as Hα and Paβ [1]. The authors compared these spectra and light curves with local core-collapse supernovae and classified Ares as a Type IIb supernova [1]. It is the highest-redshift member of this class identified spectroscopically [1].

A comparison with local SN IIb light curves gives a phase estimate for the spectrum of 34 (+10/−9) rest-frame days after the radioactive peak [1]. According to the authors, this offers a view of a high-redshift stripped-envelope supernova in its late-photospheric evolution [1].

## Lens model and future images

The authors built a lens model of the cluster using recent JWST data. It indicates that SN Ares is the first image to arrive [1]. Two further images are predicted to appear near the center of the cluster plane in ≳70 years, with magnifications of about 5× and about 1.5× [1]. Interesting Engineering cites expected delays of 73 and 76 years and describes them as the longest predicted delays among the lensed supernova systems discovered so far.

Planned JWST/NIRSpec multi-object spectroscopy of the cluster should allow more detailed modeling of the lensed system [1]. The authors expect it to give tighter constraints on the time delay and magnifications, and a template spectrum at the location of SN Ares [1]. The same outlet reports that further spectroscopic measurements are planned for 2027.

## Sources

1. [arXiv (Cornell University)](https://doi.org/10.48550/arXiv.2610.33161)
2. [Interesting Engineering](https://interestingengineering.com/science/gravitational-lensing-see-supernova-again-70-years)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-836e088710796bb4a347c24e_jwst_spectroscopy_identifies/