Giant Invisible Cloud Discovered Near Earth

A massive molecular cloud, hidden from scientists until now, has been discovered just 300 light years from our solar system. Named “Eos” after the Greek goddess of dawn, this hydrogen-rich structure could transform our understanding of star formation and interstellar space.

The international team led by Rutgers University-New Brunswick astrophysicist Blakesley Burkhart made this groundbreaking discovery using an innovative approach – detecting hydrogen molecules through their ultraviolet glow rather than relying on traditional carbon monoxide signatures.

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

Eos is massive – spanning about 40 moons across the night sky with a mass approximately 3,400 times that of our sun. Despite its enormous size, the cloud remained undetected until now because it’s mostly “CO-dark,” containing little of the carbon monoxide traditionally used to spot such formations.

The crescent-shaped cloud sits at the edge of the Local Bubble, a vast gas-filled cavity that contains our solar system. Scientists estimate it will evaporate in approximately 6 million years, but during its lifetime, Eos provides astronomers with an unprecedented opportunity to study molecular gas dynamics up close.

“When we look through our telescopes, we catch whole solar systems in the act of forming, but we don’t know in detail how that happens,” Burkhart explained. “Our discovery of Eos is exciting because we can now directly measure how molecular clouds are forming and dissociating, and how a galaxy begins to transform interstellar gas and dust into stars and planets.”

Thavisha Dharmawardena, a NASA Hubble Fellow at New York University and co-first author of the study published in Nature Astronomy, highlighted the potential significance: “The use of the far ultraviolet fluorescence emission technique could rewrite our understanding of the interstellar medium, uncovering hidden clouds across the galaxy and even out to the furthest detectable limits of cosmic dawn.”

The discovery was made possible by analyzing data from a far-ultraviolet spectrograph called FIMS-SPEAR that operated on the Korean satellite STSAT-1. This instrument breaks down ultraviolet light into its component wavelengths, creating spectra scientists can analyze to detect molecules not visible through conventional methods.

What makes this discovery particularly remarkable is the ancient nature of the hydrogen being observed. “The story of the cosmos is a story of the rearrangement of atoms over billions of years,” said Burkhart. “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. So, it’s been a long journey of 13.6 billion years for these hydrogen atoms.”

The team is now scouring data for more molecular hydrogen clouds, both near and far. Using the James Webb Space Telescope, they may have already identified the most distant molecular gas yet discovered, effectively bookending their research by finding both some of the closest and farthest hydrogen molecules from our sun.

This discovery not only expands our understanding of the molecular universe but also demonstrates how innovative observational techniques can reveal cosmic structures that have been hiding in plain sight all along.