Scientists Discover Massive Ultraviolet Molecular Cloud “Eos” Near Earth

New Discovery Illuminates a Hidden Giant in the Cosmos

An astonishing discovery by an international group of scientists, including Erika Hamden from the University of Arizona, has unveiled one of the largest molecular clouds ever observed. This remarkable find, named “Eos,” is not only a massive structure but also one of the closest molecular clouds to Earth, offering a fresh perspective on the vast universe that surrounds us.

Previously undetectable through conventional telescopic means, Eos reveals itself only in the ultraviolet spectrum, suggesting the existence of more such colossal clouds, luminous and energetic, lurking unseen in the cosmic neighborhood.

“Looking at the universe in the ultraviolet really changes how we see these molecular clouds. With infrared instrumentation, you kind of see through them. But in the UV, we can begin to make out the actual surface and structure,” explained Hamden, who serves as an associate astronomy professor at Steward Observatory and directs the U of A Space Institute.

Contained within Eos are molecular hydrogen and other compounds like carbon monoxide, key elements in star and planet formation. While traditional methods rely on radio and infrared signals to detect such clouds, this study took a novel path.

Lead study author Blakesley Burkhart shared, “This is the first-ever molecular cloud discovered by looking for far ultraviolet emission of molecular hydrogen directly. The data showed glowing hydrogen molecules detected via fluorescence in the far ultraviolet. This cloud is literally glowing in the dark.”

Located roughly 300 light-years away, Eos resides near the Local Bubble, a region filled with gas that includes our solar system. Its mass is estimated at 3,400 times that of the sun, and it is predicted to dissipate after about 6 million years.

The revelation of Eos came from data gathered by the FIMS-SPEAR, a far-ultraviolet spectrograph aboard the Korean satellite STSAT-1. This instrument breaks down ultraviolet light into its constituent wavelengths, allowing scientists to analyze the light spectrum.

Eos, predominantly made of molecular hydrogen, is “CO-dark,” lacking significant amounts of carbon monoxide, which makes it undetectable by conventional means. This discovery underscores the need for innovative techniques in astrophysical research, as noted by Burkhart.

“The story of the cosmos is a story of the rearrangement of atoms over billions of years,” Burkhart reflected. “The hydrogen that is currently in the Eos cloud existed at the time of the Big Bang and eventually fell onto our galaxy and coalesced nearby the sun.”

With advancements since the STSAT-1’s launch, researchers at Steward Observatory, led by Hamden, are poised to expand the study of molecular clouds. Hamden is preparing a proposal for a NASA mission, also named Eos, to further explore the Milky Way’s molecular hydrogen and star formation processes.

If approved, this mission could provide unprecedented insights into star-forming regions, offering a detailed view of cosmic structures. “We’d be seeing much finer details with much higher resolution, getting a multidimensional view of these really important structures,” Hamden noted. “There’s so much unexplored space in the ultraviolet. I wonder how many more things like the Eos cloud are just waiting for us to look at them in the right way.”