SN 2026aaiv in NGC 7331 – A Type Ia Supernova
Key Scientific Data
Object type: Type Ia supernova
Official designation: SN 2026aaiv
Initial survey designation: ATLAS26krw
Host galaxy: NGC 7331
Constellation: Pegasus
Distance from Earth: approximately 45–46 million light-years
Supernova type: Type Ia
Discovery: ATLAS survey
Discovery date: September 1, 2026 at 11:23:32 UT
Discovery magnitude: approximately 17.3 in the ATLAS orange filter
Right Ascension: 22h 37m 05.63s
Declination: +34° 24′ 35.2″
Redshift: approximately 0.003
Observation shown here: September 5, 2026
Host galaxy type: unbarred spiral galaxy
Light-travel time: approximately 45 million years
The Transient Name Server records SN 2026aaiv as a Type Ia supernova in NGC 7331, discovered by ATLAS on September 1, 2026 at magnitude 17.325. (Wis-TNS)
Description
SN 2026aaiv is a Type Ia supernova that appeared in the spiral galaxy NGC 7331 in the constellation Pegasus.
It was discovered by the automated ATLAS survey on September 1, 2026, when it was still relatively faint at approximately magnitude 17.3. Over the following days it brightened rapidly as the explosion developed. (Wis-TNS)
This image was obtained on September 5, only four days after the discovery, providing an early photographic record of the event.
The supernova appears as a new point of light projected against the bright inner region of NGC 7331.
The comparison with images obtained in July 2026 makes the event particularly clear: in the earlier image there is no corresponding bright stellar point, while in the September 5 image SN 2026aaiv is unmistakably visible.
Two photographs taken only weeks apart therefore record an enormous physical event that actually occurred tens of millions of years ago.
Before and After the Explosion
The comparison presented here provides a particularly direct demonstration of what a supernova actually looks like observationally.
The left-hand image is a stack of 60 × 300-second luminance exposures obtained on July 15, 16, 17, 18 and 19, 2026.
At that time, no supernova is visible at the position later occupied by SN 2026aaiv.
The right-hand image consists of 6 × 300-second luminance exposures obtained on September 5, 2026.
A new point source has appeared within NGC 7331.
The arrow indicates SN 2026aaiv.
The two images were therefore taken less than two months apart from Earth, yet they record the sudden appearance of one of the most energetic stellar explosions in the Universe.
What Is a Type Ia Supernova?
A Type Ia supernova is fundamentally different from the explosion produced by the core collapse of a massive star.
Its origin involves a white dwarf — the extremely compact remnant left behind after a lower-mass star has completed its normal evolution.
A white dwarf can contain a mass comparable to that of the Sun compressed into an object roughly the size of Earth.
Under certain circumstances, interaction with a companion star or another white dwarf can drive the system toward conditions that trigger catastrophic thermonuclear burning.
Carbon fusion ignites explosively and a runaway thermonuclear reaction propagates through the white dwarf.
Within seconds, an enormous amount of nuclear energy is released.
The white dwarf is disrupted in the explosion.
Unlike some core-collapse supernovae, which can leave behind a neutron star or black hole, a normal Type Ia event is expected to destroy the exploding white dwarf.
A Star Becoming Billions of Times Brighter
A Type Ia supernova can temporarily reach a luminosity of billions of Suns.
For a short period, a single exploding star can therefore become comparable in brightness to a substantial fraction of the galaxy containing it.
This extraordinary luminosity explains why supernovae can be detected across enormous cosmological distances.
In the case of SN 2026aaiv, the explosion occurred in a galaxy approximately 45 million light-years away, yet it is clearly detectable with amateur-class astronomical equipment.
The enormous distance also provides an important sense of scale.
The apparently tiny point identified by the arrow is not a foreground star in our Milky Way.
It is an exploding stellar remnant inside another galaxy containing billions of stars.
NGC 7331 – The Host Galaxy
NGC 7331 is one of the most beautiful spiral galaxies visible in the northern sky.
Located in Pegasus, it lies roughly 45 million light-years from Earth and is seen at a steep inclination, giving it its characteristic elongated appearance.
Its bright central bulge contains predominantly older stellar populations, while its disc contains extensive dust lanes and regions of younger stars.
Several much smaller-looking galaxies are visible around NGC 7331.
Despite their apparent proximity in the photograph, some are actually much farther away and do not form a single physical system with NGC 7331.
The field therefore provides a remarkable perspective on cosmic distance: foreground stars belonging to our Milky Way, NGC 7331 tens of millions of light-years away, and more distant background galaxies can all appear within the same photograph.
Two Type Ia Supernovae in Two Years
SN 2026aaiv has an especially interesting recent predecessor.
In 2025, NGC 7331 hosted another Type Ia supernova, SN 2025rbs.
The appearance of two Type Ia supernovae in the same prominent galaxy in consecutive years is an unusual observational coincidence and has made NGC 7331 particularly interesting to supernova observers. (Fisica Purdue)
It is also an excellent reminder that a galaxy is not a static object.
Even when its overall appearance seems unchanged from night to night, billions of stars are evolving within it.
Occasionally, one undergoes an event energetic enough to become visible across tens of millions of light-years.
ATLAS – The Survey That Found It
SN 2026aaiv was discovered by ATLAS, the Asteroid Terrestrial-impact Last Alert System.
ATLAS is a robotic astronomical survey originally designed primarily to detect potentially hazardous asteroids approaching Earth.
Its telescopes repeatedly scan enormous areas of the sky, searching for objects whose positions or brightness change.
That capability also makes ATLAS extremely effective at discovering transient astronomical phenomena.
Supernovae suddenly appear.
Variable stars change brightness.
Comets and asteroids move against the stellar background.
On September 1, 2026, this continuous monitoring detected the new transient in NGC 7331 that subsequently received the official designation SN 2026aaiv. (Wis-TNS)
How Do We Know It Is a Type Ia?
A photograph can reveal that a new source of light has appeared, but determining the physical nature of a supernova requires spectroscopy.
Astronomers separate the light of the object into its component wavelengths and examine the resulting spectrum.
Type Ia supernovae have characteristic spectral signatures, most famously strong absorption associated with ionised silicon near maximum light and the absence of the prominent hydrogen features characteristic of many core-collapse supernovae.
Spectroscopic observations obtained shortly after the discovery of SN 2026aaiv confirmed its classification as a Type Ia supernova. (Wis-TNS)
This illustrates the complementary roles of astrophotography and spectroscopy.
An image tells us where the supernova is and how its brightness changes.
A spectrum helps tell us what kind of explosion we are observing.
Supernovae as Cosmic Distance Markers
Type Ia supernovae have played an extraordinary role in modern cosmology.
Because their intrinsic luminosities can be standardised from their observed light curves and colours, astronomers can use them as standardisable candles.
If we know approximately how luminous an event really is and measure how faint it appears from Earth, we can estimate its distance.
Observations of distant Type Ia supernovae in the late twentieth century led to one of the most important discoveries in modern cosmology: the expansion of the Universe is accelerating.
The phenomenon responsible for this acceleration is described by the term dark energy.
The tiny point of light visible in this photograph therefore belongs to the same class of astronomical events that fundamentally changed our understanding of the evolution of the Universe.
The Elements Created in the Explosion
Type Ia supernovae are also important contributors to the chemical evolution of galaxies.
The thermonuclear explosion produces large quantities of elements belonging to the iron group, together with intermediate-mass elements.
The explosion ejects this newly processed material into interstellar space at enormous velocities.
Over time, those elements mix with surrounding gas.
Future generations of stars and planetary systems can incorporate them.
Much of the iron present in planets such as Earth ultimately owes its existence to earlier generations of stellar explosions, including Type Ia supernovae.
An event like SN 2026aaiv is therefore simultaneously an act of stellar destruction and part of the long-term chemical enrichment of its galaxy.
Curiosities
The official name SN 2026aaiv follows the international naming system for supernovae.
“SN” identifies the object as a supernova, while “2026” indicates the year in which it was reported.
The sequence of letters identifies its position in the chronological sequence of supernovae reported during that year.
At discovery the object was only about magnitude 17.3, but it subsequently brightened dramatically. Observations during the following days showed it climbing through the amateur-observable magnitude range. (Wis-TNS)
The comparison image is particularly valuable because the July observations provide a genuine pre-supernova reference obtained with the same observatory.
The September photograph is therefore not merely an image of a supernova.
It documents an actual astronomical change in another galaxy.
Looking Back in Time
Perhaps the most extraordinary aspect of this photograph is that SN 2026aaiv did not actually explode in September 2026.
That is simply when its light reached Earth.
NGC 7331 is approximately 45 million light-years away.
The explosion therefore occurred roughly 45 million years ago. (Space)
When the white dwarf was destroyed, there were no humans on Earth.
There were no hominins.
Our primate ancestors were still undergoing their early evolution, and the continents and ecosystems of Earth looked very different from those of today.
The photons produced by the explosion then began travelling through intergalactic space at 299,792 kilometres per second.
Year after year they continued toward the Milky Way.
Millions of years passed.
Species evolved and disappeared.
Eventually humans appeared.
Civilisations arose.
Astronomy developed.
Telescopes were invented.
Photography was invented.
Electronic astronomical cameras were developed.
And finally, after approximately 45 million years of uninterrupted travel, some of those photons reached Earth.
On September 5, 2026, a tiny fraction entered the Artesky ARTEC 250 Pro at the Innumerabili Mondi Observatory and ended their journey on the sensor of the Player One Poseidon-M Pro.
The exposure lasted only 30 minutes in total.
The journey of the light recorded during those 30 minutes had lasted approximately 45 million years.
The explosion lasted moments. Its light crossed a galaxy-sized gulf of time before reaching this photograph.
Image Data
Total integration time: 30m
Integration by filter:
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Luminance / Clear: 30m (6 × 300")
Equipment:
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Telescope: Artesky ARTEC 250 Pro
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Camera: Player One Poseidon-M Pro
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Mount: 10Micron GM2000 HPS II
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Filter: Antlia V-Pro Luminance 2"
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Accessories: Pegasus Astro Prodigy Microfocuser, Player One Phoenix Wheel 7×2″, WandererAstro WandererCover V4-EC
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Software: Adobe Photoshop, Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)
Comparison image:
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Before: stack of 60 × 300 s luminance exposures — July 15, 16, 17, 18 & 19, 2026
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After: stack of 6 × 300 s luminance exposures — September 5, 2026
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SN 2026aaiv: indicated by the arrow in the September image
For further information and the full-resolution image, visit AstroBin: