Astronomers Find One of the Faintest Galaxies Ever, an Ancient Speck Orbiting Andromeda With Just 46 Stars
So dim it nearly escaped detection, the newly confirmed dwarf galaxy And 35 is about 12.5 billion years old and offers a rare window into the universe's first generations of stars — and the nature of dark matter.
Astronomers have confirmed one of the faintest galaxies ever found — a ghostly clump of just 46 detectable stars orbiting our giant neighbor, the Andromeda galaxy. Cataloged as Andromeda XXXVI, or And 35, the object is so dim it very nearly slipped past detection entirely, and its discovery pushes the limits of what modern telescopes can see.
The trail began not with a professional survey but with a sharp-eyed amateur. Italian astronomer Giuseppe Donatiello spotted a faint smudge while visually combing through publicly available images from the Pan-Andromeda Archaeological Survey, a deep imaging campaign that maps the halo of stars surrounding Andromeda. Professional astronomers then followed up, obtaining deep images on January 22, 2026, with the OSIRIS+ instrument on the Gran Telescopio Canarias in the Canary Islands — one of the largest optical telescopes on Earth — to confirm the find.
What they confirmed is a genuine relic. The galaxy's stars are extremely poor in heavy elements, with a measured metallicity around -2.5, a signature of stars that formed before the cosmos had been enriched by generations of stellar explosions. Its age is estimated at about 12.5 billion years, meaning And 35 took shape when the universe was less than a fifth of its current age. Objects like it are essentially fossils, preserving the conditions of the early universe in a way that larger, still-evolving galaxies cannot.
Ultra-faint dwarf galaxies are also among astronomers' best natural laboratories for studying dark matter, the invisible substance thought to make up most of the universe's mass. These tiny systems hold so few stars that their gravity should have flung them apart long ago — unless they are bound together by enormous, unseen halos of dark matter. By weighing And 35 and its handful of stars, researchers can probe how dark matter behaves on the smallest cosmic scales, a regime where leading theories are hardest to test.
The discovery also sharpens a running puzzle about Andromeda itself. Astronomers estimate the galaxy hosts roughly 92 dwarf companions, but only about 40 have been confirmed, and just 15 of those are ultra-faint. Each new detection like And 35 helps fill in the census and test whether the number and arrangement of these satellites match what cosmological simulations predict — a comparison that has, at times, strained the standard model of how galaxies assemble.
Published in the journal Astronomy & Astrophysics, the finding is a reminder that even in the era of billion-dollar observatories, transformative discoveries can still begin with a patient human eye scanning the archives. And 35 will now join a small, precious catalog of the dimmest galaxies known — faint fossils that, despite holding barely enough stars to count on a spreadsheet, carry outsized clues about how the universe grew up.
Originally reported by Phys.org.