A team of astronomers led by Rutgers University scientists says they discovered a previously invisible object near our solar system when they realized it emits radiation in the far ultraviolet frequency, making it glow.
Dubbed “Eos” for the ancient goddess of Greek mythology that personified creation, the massive molecular cloud is the first time such an object was spotted by hunting for signs of molecular hydrogen at this wavelength in the spectrum, potentially adding a unique approach to the arsenal of astronomers and cosmologists.
“This is the first-ever molecular cloud discovered by looking for far ultraviolet emission of molecular hydrogen directly,” explained project leader Blakesley Burkhart, an associate professor in the Department of Physics and Astronomy in the Rutgers School of Arts and Sciences and a co-author on the study detailing the discovery. “This cloud is literally glowing in the dark.”
The Invisible Object Near Our Solar System Was Always Glowing in the Dark
According to a press release announcing the discovery, Eos is a crescent-shaped cloud of gas and dust roughly 300 light years from Earth, making it relatively close, cosmically speaking. In fact, the previously invisible object near our solar system, which has an estimated mass of around 3,400 suns, sits at the edge of an area of space astronomers call the Local Bubble, placing it in the same general region as the solar system.
The data revealing the location of the invisible object was originally captured by a far-ultraviolet spectrograph called FIMS-SPEAR (fluorescent imaging spectrograph) that operated as an instrument on the Korean satellite STSAT-1. Publicly released in 2023, Burkhart says no one had searched through it the way her team wanted to.
“[The data] was kind of like just waiting to be explored,” she said.
While most molecular clouds are detected by their radio and infrared emissions, scans in this region of space hadn’t indicated the presence of a molecular gas cloud. When Burkhart and colleagues scanned the data in the far ultraviolet spectrum, an object that had previously been invisible was suddenly glowing.
“The data showed glowing hydrogen molecules detected via fluorescence in the far ultraviolet,” the Rutgers astronomer, who is also a research scientist at the Center for Computational Astrophysics at the Flatiron Institute in New York, explained.
‘CO-Dark’ and the Far Ultraviolet Glow
The study authors suggest Eos is probably difficult to detect by traditional means because it is described as “CO-dark.” This designation means it contains very little CO and therefore doesn’t emit the same ‘telltale’ signature as a typical molecular cloud of this size and proximity. The team also says the detection of the cloud using the far ultraviolet spectrum is novel since it was previously believed that searching for these types of glowing objects in that range was impossible.
“When I was in graduate school, we were told that you can’t easily directly observe molecular hydrogen,” said NYU researcher Thavisha Dharmawardena, a NASA Hubble Fellow at New York University and a shared first author of the study. “It’s kind of wild that we can see this cloud in data that we didn’t think we would see.”
Like Burkhart, the NYU researcher believes that hunting for cosmic phenomena in this novel spectrum could offer astronomers a fresh new tool to study previously invisible objects that are actually glowing in the dark.
“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,” Dharmawardena said.
“This opens up new possibilities for studying the molecular universe,” said Burkhart.
EOS Poses No Danger But Offers Unique Opportunity
The study authors said Eos poses no danger to the solar system. However, spotting this unique cloud of molecular gas so close to home offers a unique opportunity to study the properties of a structure wandering within the interstellar medium.
“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 said. “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.”
The authors also say that research efforts like theirs, which study previously invisible objects that are relics of the dawn of the cosmos, allow scientists to travel back in virtual time to study how the universe began.
“The story of the cosmos is a story of the rearrangement of atoms over billions of years,” Burkhart said. “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.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.
