'Fossil Galaxy' Hasn't Changed in 7B Years

Astronomers have identified a rare "fossil galaxy" named KiDS J0842+0059, located about 3 billion light-years from Earth, providing a unique window into the early universe. This galaxy, unchanged for roughly 7 billion years, stands out as the most distant relic galaxy detected beyond our local cosmic neighborhood. Fossil galaxies, also known as relic galaxies, are unusual: after an initial period of rapid star formation, they remain largely dormant, escaping the mergers and growth typical of most galaxies, CNN reports. Such galaxies are extremely rare. Researchers estimate that only one in a few million galaxies in a relic galaxy.

Researchers from the Italian National Institute for Astrophysics used high-resolution images from Arizona's Large Binocular Telescope to confirm the galaxy's status. These galaxies are compact, dense, and filled with ancient stars, but show little to no new star formation—a kind of cosmic archive. "They're essentially doing nothing and are the fossil records of the very ancient universe," Chiara Spiniello, co-author of a study published in the Monthly Notices of the Royal Astronomical Society. "This is what we call an extreme relic because almost all, or 99.5% of its stars were formed incredibly early on in cosmic time, and the galaxy did absolutely nothing thereafter," she says.

"Fossil galaxies are like the dinosaurs of the universe: studying them allows us to understand in which environmental conditions they formed and how the most massive galaxies we see today evolved," says Crescenzo Dove, another co-author, per Space.com. Scientists believe such galaxies formed most of their mass in a quick, early burst, then largely avoided the second phase of galactic evolution that involves mergers and dramatic shape changes. What prevents them from merging with neighbors remains a mystery, though feedback from supermassive black holes is a leading theory.

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Spiniello says the galaxy will have planets, but they will be very hard to spot because it is so much denser than our own. "There will be many more stars in a tiny, tiny volume, so it'll be super crowded," she says. Researchers are seeing KiDS J0842+0059 as it was 3 billion years ago, not as it is today, but Spiniello says it could remain unchanged indefinitely.