A population census, but instead of houses (galaxies, and instead of residents) stars. Astronomers set out to count the smallest and faintest "homesteads" in our cosmic neighborhood: dwarf galaxies. They are thousands of times fainter than the Milky Way, and spotting them in images is as hard as picking out a firefly in front of a spotlight.

For the search, they used a special algorithm that scans images for barely visible clumps of light. To test how well it works, they artificially added fake galaxies to the images and checked how many the algorithm could detect. It turned out to reliably find half of the dwarfs with a mass of about a million suns, like finding a person of below-average height in a crowd if they're standing in a dark corner.

But it's not enough to spot a faint smudge: you need to confirm it's truly a nearby dwarf galaxy, not a distant bright object that only appears faint. To do this, distances were measured in three ways: by redshift (how fast the galaxy is receding), by the brightness of its oldest stars, and by characteristic fluctuations in surface brightness. In the end, they confirmed 95 genuine dwarfs within 30 million light-years of us.

The most interesting finding concerns the loners. Of the 95 galaxies, 44 turned out to be completely isolated — with no large neighbor for millions of light-years around. That's a rare stroke of luck: previously, such objects were found one at a time, but now there's a whole collection. By comparing their masses, astronomers built a "population census" of dwarfs and found that in the high-mass range it matches the predictions of the IllustrisTNG computer model of the universe remarkably well. This means our understanding of how small galaxies are born and live is essentially correct.

Now these lonely dwarfs will serve as a testing ground for theories: how the absence of neighbors affects star formation, shape, and the fate of a galaxy. Because even in space, loneliness changes a lot.