The molecular cloud is filled with enough material to potentially give rise to newborn stars.
Stars are born within immense, cold clouds of gas and dust that gradually collapse under their own gravity. These molecular clouds are colossal structures, often spanning hundreds of light-years, and scientists have just identified a huge one in our cosmic backyard.
Named Eos—after the Greek goddess of dawn—the cloud lies roughly 300 light-years from our solar system. It’s one of the largest single features in the sky and might be the closest known molecular cloud to Earth, according to a study recently published in Nature Astronomy. Its proximity provides astronomers with a rare, close-up opportunity to study the star formation process and gain insight into the molecular environment of our galaxy.
In our corner of the Milky Way, stellar nurseries typically form along the boundary of the Local Bubble—a vast, hot region of plasma surrounded by a shell of gas and dust. To find molecular clouds in this region, scientists have traditionally relied on detecting emissions from interstellar dust. However, this new discovery was made by observing the far-ultraviolet fluorescence emitted by molecular hydrogen, as detailed in the study.
“This is the first time a molecular cloud has been discovered by directly detecting far-ultraviolet emission from molecular hydrogen,” said Blakesley Burkhart, a physics and astronomy professor at Rutgers and the lead author of the study.
Molecular hydrogen—composed of two hydrogen atoms bonded together—is the most common molecule in the universe, but it’s notoriously difficult to spot because it emits in the far-ultraviolet range, which Earth’s atmosphere blocks. “The data revealed glowing hydrogen molecules visible through far-ultraviolet fluorescence,” Burkhart explained. “This cloud is, quite literally, glowing in the dark.”
Besides its luminescent quality, Eos has a crescent-like shape and sits along the edge of the Local Bubble. It spans an area equivalent to 40 full Moons in the sky and has a mass roughly 3,400 times that of our Sun. The same technique used to detect Eos could potentially unveil more hidden molecular clouds across the Milky Way.
“When we observe the skies, we can witness entire solar systems in the making, but the detailed mechanics of how that happens remain elusive,” Burkhart noted. “The discovery of Eos is thrilling because it allows us to directly track how molecular clouds form and break apart, offering key insights into how galaxies convert interstellar gas and dust into stars and planets.”
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