 |
| Black and White image with negative of NGC 7331 showing location of SN 2025rbs. Data credit: PIRATE robotic telescope on Mount Teide Tenerife - clear filter. telescope.org, Open Observatories, Open University. Image credit: Kurt Thrust |
 |
| An enlargement showing the supernova the bright white dot to the left of the galaxy core. |
" We are awaiting colour data taken with the same telescope with BVR filters and will add to this post as and when available.
The supernova can be seen in the above as a bright spot close to the bright central core of the galaxy NGC 7331.
An overview by visiting astrophysicist - Professor G.P.T Chat and our outreach officer at the JPO - Karl Segin.
A New Supernova in NGC 7331: SN 2025rbs
A new supernova, called SN 2025rbs, recently went off in the spiral galaxy NGC 7331, about 40 million light-years away in the constellation Pegasus. This galaxy is often described as a sort of “twin” to our own Milky Way—it’s similar in structure and size—so it’s always of interest when something exciting happens there.
How It Was Found
The supernova was first spotted on July 14, 2025, by the GOTO (Gravitational-wave Optical Transient Observer) project. They flagged it as a new, brightening light source in NGC 7331 and gave it a temporary ID (GOTO25evh) before it was officially confirmed and named SN 2025rbs.
Since then, astronomers around the world—both professionals and amateurs—have been watching it closely as it continues to brighten in the night sky.
What Kind of Supernova Is It?
SN 2025rbs has been classified as a Type Ia supernova. This type of explosion happens when a white dwarf star—a dense remnant of a dead star—accumulates too much material from a nearby companion star. When it reaches a critical mass (about 1.4 times the mass of the Sun), the pressure and temperature inside trigger a runaway thermonuclear explosion.
That explosion destroys the white dwarf completely and releases a huge amount of energy, making these some of the brightest events in the universe. In fact, Type Ia supernovae are so reliably bright that astronomers use them as “standard candles” to measure distances across the cosmos.
What's Happening Physically?
Inside the explosion, new elements are forged—especially nickel-56 (^56Ni), which quickly decays into cobalt and then into stable iron (^56Fe). These radioactive decays release energy in the form of gamma rays, which get absorbed and re-emitted as visible light. That’s what makes the supernova so bright for several weeks.
How Bright Is It?
As of late July, SN 2025rbs has reached around magnitude 11.8 in visible light, making it one of the brightest supernovae currently visible in the sky. That’s well within range for amateur astronomers with moderate-sized telescopes. It’s sitting just about 13 arcseconds from the galaxy’s bright core, which makes it a little tricky to spot—but with the right tools, it’s definitely observable.
This brightness matches what we’d expect from a Type Ia supernova at that distance—it should reach an absolute magnitude around −19.3, which is incredibly luminous.
Space Telescopes Get Involved
The NuSTAR space telescope, which observes in X-rays, quickly turned its attention to the event. It’s looking for high-energy X-rays and gamma rays from the radioactive material in the explosion. Observations like this can help scientists learn about the shape of the explosion and the amount of nickel produced, which gives clues about how these events unfold.
Why This Supernova Is a Big Deal
This is the fourth supernova ever recorded in NGC 7331, but it’s the first one of the Type Ia variety. That alone makes it valuable for scientific study. But the fact that it’s so close (in cosmic terms) and so bright makes it a golden opportunity.
Researchers are using this event to:
-
Test and refine how we measure distances in the universe.
-
Study the physics of white dwarf explosions.
-
Compare it to other Type Ia supernovae to learn more about what makes them tick.
-
Observe it across multiple wavelengths—optical, X-ray, and more.
Plus, it’s a great example of how professional and amateur astronomers can collaborate: GOTO made the initial discovery, professionals classified it, and amateur observers have been following its progress every clear night since.
Scientific Summary
-
Host Galaxy: NGC 7331, unbarred spiral at ~40 Mly.
-
Explosion: Type Ia triggered by a white dwarf exceeding mass limit.
-
Timeline: Discovered ~14 July 2025; rise to peak over ~20 days.
-
Peak Brightness: ~11–12 mag apparent; absolute magnitude near −19.3.
-
Scientific Utility: Benchmarks Type Ia standard candles; close enough for multiwavelength study (optical, photometry, spectroscopy, X‑rays).
