When a galaxy flickers: NGC 7331 and supernova SN 2025rbs

Between late July and August, I pointed one of the telescopes—which will soon have a home of their own—at the galaxy NGC 7331 in Pegasus. I used the Sky-Watcher 200 PDS , along with the ASI 533MC Pro camera and the L-Quad Enhance filter on the EQ6R Pro. With this equipment, I accumulated more than 10 hours of exposure under a Bortle 4.5 sky.

The initial idea was simple: to test the performance of this Newtonian telescope we had recently installed. But the next morning, while searching for information about the galaxy, I discovered something that left me speechless: a supernova explosion, SN 2025rbs , had occurred in NGC 7331 .

Not only was I photographing a beautiful galaxy… I had also captured a dying star.

NGC 7331: The Distant Sister

About 50 million light-years away, NGC 7331 is a majestic spiral, sometimes compared to the Milky Way. Its arms extend outward, filled with gas and dust, and its core holds a curious secret: it rotates in the opposite direction to the galactic disk.

It's one of those objects always worth observing. But this time, in addition to its usual beauty, it brought with it a new story.

NGC 7331 and Deer Lick Group

SN 2025rbs: A Spark in the Darkness

The SN 2025rbs supernova was officially discovered on July 14, 2025. It is a Type Ia supernova, meaning the explosion of a white dwarf that reached its limit after stealing material from its companion star. A cosmic explosion capable of releasing as much energy as the entire galaxy in which it lives.

For a few weeks, it shone at magnitude 11-12, enough for even modest equipment to detect it. In my image, that tiny dot next to the galaxy's arms represents a colossal event: the death of a star and, at the same time, the seeding of elements that could one day form planets, atmospheres, and even life.

What it means to me

I started this capture simply as a technical test. And without realizing it, I ended up recording one of the most spectacular phenomena we can observe: a supernova.

That's what fascinates me about astrophotography: you never know what story awaits you in the sky. With patience, technique, and a little luck, we can witness fleeting chapters in this immense book that is the universe.

For subscribers

Subscribers can now download the full data set : all the original images from this project, ready for processing. If you enjoy both processing and observing, this is your chance to give your own interpretation to NGC 7331 and the supernova SN 2025rbs .

If you're not yet a subscriber, I invite you to join: you'll not only have access to this dataset, but also to upcoming and existing ones.

The sky never ceases to remind us that it's alive, that it changes, that every night it can surprise us. This time it was a galaxy and a supernova. The next time... who knows?

Thank you for joining me on this stellar journey, Alberto Pisabarro.