Astronomers might have found the closest thing yet to a galaxy that, like your slacker sibling, simply refused to get its s—t together and grow up.
Publishing their findings in The Astrophysical Journal Letters, researchers say it’s a gigantic space object called Cloud-9 that’s about 14.3 million light-years away, near the spiral galaxy M94. It’s got all the dense hydrogen gas clouds wrapped around masses of dark matter, but no stars to show for it.
First detected by China’s FAST radio telescope, Cloud-9 is filled with neutral hydrogen. That means the gas is cool and compact, rather than blasted apart or ionized by radiation from nearby stars. It can’t be because there aren’t any. Follow-up observations using a variety of telescopes around the world, including our own Hubble Space Telescope, confirmed the weirdness that China found.
Astronomers Just Found a Galaxy That Never Formed
The cloud is roughly 4,900 light-years wide, holds about a million Suns’ worth of gas, shows no signs of rotation, and would require roughly five billion solar masses of dark matter to stay intact.
Hubble’s deep optical imaging turned up nothing resembling a galaxy. If Cloud-9 contains stars at all, astronomers say it can’t be more than a few thousand Suns’ worth. Sounds like an enormous amount, but astronomically speaking, that’s unremarkable at best.
Researchers believe Cloud-9 is the clearest example yet of a long-theorized object called a Reionization-Limited H I Cloud, or RELHIC. That’s a dark-matter-dominated clump of gas that never fully transformed into a star. Other candidates for this highly specialized category exist, but they often eventually turn out to have some star, maybe a little rotation. Cloud-9 checks all the boxes.
It is a failed galaxy, according to the researchers. But it’s probably more accurate to call it a fossil left over from the early days of the universe, when it was still getting its act together. It’s possible that Cloud-9 could eventually light up with stars. Just as it’s possible that it could just remain dead forever.
Either way, it offers us a glimpse at how galaxies form, and how sometimes they don’t.
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