A new class of galaxies, nicknamed UFOs -- short for Ultra-red Flattened Objects -- has been discovered by astrophysicists led by the University of Colorado Boulder (CU Boulder).
These mysterious galaxies, first spotted using the James Webb Space Telescope (JWST), are large, red, and incredibly dusty.
Unlike alien spacecraft, these UFOs are enormous galactic disks that were invisible to earlier telescopes, like the Hubble Space Telescope.
"JWST lets us see galaxies we couldn't detect before," said Justus Gibson, the study's lead author and a doctoral student in astrophysics. "It shows us that we may not understand the universe as well as we thought."
The team's research, published in The Astrophysical Journal, reveals that UFO galaxies are similar in size and shape to the Milky Way but contain much more dust, blocking most of their visible light.
Why are UFO galaxies so unique?
UFO galaxies are "hidden" because they emit very little visible light. Instead, most of their light escapes as infrared radiation, which is invisible to the human eye.
The Hubble telescope, which captures visible light, missed these galaxies entirely. However, JWST, launched in 2021, is designed to detect infrared light, making it ideal for uncovering these hidden objects.
"They're enormous red disks that completely surprise us," said Erica Nelson, a co-author and assistant professor of astrophysics at CU Boulder. "You look at these images, and they make you think, 'What? How?'"
Using data from the JWST Advanced Deep Extragalactic Survey (JADES), the researchers identified 56 UFO galaxies.
They found that these galaxies are packed with dust -- about 50 times more than the Milky Way. This dust comes from tiny particles released by dying stars. It's so thick that it blocks most of the light, similar to a sandstorm on Earth hiding the sun.
What do they look like?
Despite their odd nickname, UFO galaxies may not be that different in shape from the Milky Way. Computer simulations suggest they are likely disk-shaped, much like our galaxy.
"You've got these big, dusty disks flying through space, completely invisible to earlier telescopes," Nelson said.
Mysteries of the dust
Why UFO galaxies are so dusty is still a mystery. Nelson hopes studying them will help scientists better understand how galaxies grow and form stars over time.
"For now, these galaxies raise more questions than answers," she said. "Why do they have so much dust? No idea yet."
This discovery highlights how JWST is transforming our understanding of the universe by uncovering unseen features of galaxies near and far. As researchers study UFO galaxies further, they may unlock new insights into how galaxies like our Milky Way came to be.