By Isaac Schultz Published March 13, 2025 | Comments (1) | The smallest, dimmest galaxy orbiting Andromeda to date. Image: CFHT/MegaCam/PAndAS (Principal investigator: Alan McConnachie; Image processing: Marcos Arias A group of astronomers has discovered the smallest, dimmest satellite galaxy bordering the Milky Ways nearest galactic neighbor, the Andromeda Galaxy. The itsy-bitsy satellite galaxy is named Andromeda XXXV and sits about 3 million light-years from Earth. The discovery of the galaxy gives astronomers a useful comparative tool for studying satellite galaxies on the outskirts of our own galaxy, the Milky Way. The teams findings were published this week in The Astrophysical Journal Letters. Its like having a perfectly functional human being thats the size of a grain of rice. These are fully functional galaxies, but theyre about a millionth of the size of the Milky Way, said Eric Bell, an astronomer at the University of Michigan and senior author of the study, in a university release. Its like having a perfectly functional human being thats the size of a grain of rice. Andromeda XXXV is only about 20,000 times more massive than our Sunvery small, even for a satellite galaxy. For comparison, the Milky Ways mass is about 1.5 trillion solar masses, and the beefiest galaxies can be up to 30 trillion solar masses. Though it is a full-fledged galaxy, Andromeda XXXV is small enough to be ensnared by the gravitational pull of Andromedamuch like the satellite galaxies of the Milky Way. The researchers observed Andromeda XXXV with the Hubble Space Telescope.This type of galaxy was only discoverable around one system, the Milky Way, in the past, Bell said. Now were able to look at one around Andromeda and its the first time weve done that outside our system. The Hubble observations revealed that not only was Andromeda XXXV a satellite galaxy, but it is small enough to raise questions about how such satellites even form stars.Most of the Milky Way satellites have very ancient star populations. They stopped forming stars about 10 billion years ago, said Marco Arias, the lead author of the study, in the same release. What were seeing is that similar satellites in Andromeda can form stars up to a few billion years agoaround 6 billion years. The finding is usable in differentiating satellite galaxy formation and star formation in the Milky Way from the conditions in other galaxies. There are anywhere between 100 billion to 2 trillion galaxies in the observable universe, but such small, faint galaxies are hard to seewhich is why youre hearing about the Hubble observations of Andromeda XXXV. There are still outstanding questions about the little galaxyincluding how it survived the universe heating up nearly 13 billion years ago. The entire universe turned into a vat of boiling oil, Bell said, and Andromeda XXXV is so small it couldve lost all of its gas. But for several billion years thereafter, the galaxy continued to form stars.More observations could clarify the nature of this industrious, persevering satelliteand by proxy, could shed light on the satellite galaxies swirling around the periphery of our own cosmic neighborhood.Daily NewsletterYou May Also Like By Passant Rabie Published March 12, 2025 By Passant Rabie Published March 12, 2025 By Margherita Bassi Published March 12, 2025 By Passant Rabie Published March 10, 2025 By Isaac Schultz Published February 18, 2025 By Isaac Schultz Published February 13, 2025