Image of a bright-red UFO galaxy, upper-right corner, as taken by the James Webb Space Telescope. (Credit: Nelson et al., 2023, The Astrophysical Journal Letters)
In a new study, a team of astrophysicists led by CU Boulder has set out to unravel the mysteries of UFOs—not the alien spacecraft, but a class of unusually large and red galaxies that researchers have nicknamed Ultra-red Flattened Objects, or UFOs for short.
The research shines a spotlight on some strange galaxies, said Justus Gibson, lead author of the study and a doctoral student in the Department of Astrophysical and Planetary Sciences. CU Boulder researchers first discovered UFO galaxies in images from the James Webb Space Telescope (JWST).
Now, Gibson and his colleagues think they know more about the galaxies’ inner workings.
The researchers explained that UFOs are odd cosmic ducks for various reasons. For starters, they reside near the limit of how far earlier space instruments, like the Hubble Space Telescope, could peer into the universe. But Hubble had completely missed them because these galaxies emit very little visible light.
The new study relies on observations from the Webb telescope, a pioneering spacecraft that launched in December 2021. Drawing on those images and computer simulations, the team reports that UFO galaxies seem to be similar in size and shape to the Milky Way. But these new galaxies are much dustier.
The team published its findings this October in The Astrophysical Journal.
“JWST allows us to see this type of galaxy that we never would have been able to see before,” Gibson said. “It tells us that maybe we didn't understand the universe as well as we thought.”
The universe is turning out to be more interesting than some scientists assumed, said study co-author Erica Nelson, who first discovered the UFO galaxies.
“They’re so visually striking,” said Nelson, assistant professor of astrophysics at CU Boulder. “They’re enormous red discs that pop up in these images, and they were totally unexpected. They make you say: ‘What? How?’”
Hidden galaxies
Gibson noted that UFO galaxies look red because they emit very little visible light—most of the light that escapes these galaxies is infrared radiation, and what little visible light they emit is at the limit of what human eyes can see (red, in other words). As a result, the UFO galaxies were all but invisible to Hubble, which only records visible light. The Webb telescope, in contrast, collects infrared light, which means it’s well-suited to spotting these kinds of objects.