Astronomers have discovered a massive, previously unseen cloud of gas and dust near our solar system—and it might change how we understand the space around us.
The newly found cloud, named Eos after the Greek goddess of dawn, is one of the largest known structures in the sky and one of the closest molecular clouds ever detected, sitting just 300 light-years from Earth.
What makes Eos remarkable is that it had been completely invisible to traditional telescopes. Most molecular clouds are spotted using infrared or radio waves, which pick up the carbon monoxide found in such clouds.
But Eos doesn’t contain much carbon monoxide, making it “CO-dark” and nearly impossible to find with those methods. Instead, scientists detected it by observing a different type of light: far ultraviolet.
Using a special instrument called FIMS-SPEAR aboard a Korean satellite, researchers were able to spot the glow of hydrogen molecules—known as fluorescence—shining in ultraviolet light.
This is the first time a molecular cloud has been discovered using this method.
“This cloud is literally glowing in the dark,” said Blakesley Burkhart, the lead author of the study, published in Nature Astronomy.
Erika Hamden, a University of Arizona astronomer and expert in ultraviolet observation, explained that this approach allowed scientists to finally see the cloud’s shape and surface.
To the naked eye, if it were visible, the Eos cloud would look like a giant purple cap stretching across the sky—covering an area as wide as 40 full moons.
Made mostly of molecular hydrogen, Eos holds about 3,400 times the mass of our sun. Its crescent shape appears to sit on the edge of the “Local Bubble,” a cavity in space that contains our solar system. The cloud is expected to evaporate in about 6 million years, giving scientists a rare opportunity to study its life cycle before it disappears.
For researchers, Eos is more than just a curiosity. It offers a chance to understand how clouds like it form, break apart, and eventually give birth to stars and planets. Since molecular hydrogen is the universe’s most basic building block, studying it helps explain how galaxies—and life—develop over billions of years.
Hamden and her team are now preparing to propose a new NASA mission, also called Eos, that would use updated ultraviolet instruments to search for more hidden clouds across the Milky Way. “There’s so much unexplored space in the ultraviolet,” Hamden said. “I wonder how many more clouds like Eos are out there, just waiting for us to look at them the right way.”
Source: University of Arizona.
