Scientists have made a remarkable discovery: a molecular cloud named Eos, after the Greek goddess of dawn. This discovery is remarkable because the cloud in question has been in Earth’s “cosmic backyard” but is just being discovered.

The Eos Molecular Cloud Hidden In Plain Sight

On 28 April 2025, the Nature Astronomy journal released details on a “nearby dark molecular cloud” close to Earth. This dark molecular cloud, now known as Eos, has been residing close to Earth for a while but hasn’t been discovered until now.

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According to the journal, if visible to the naked eye, this dark molecular cloud will be the size of 40 moons in width and will weigh about 3,400 times the mass of the Sun. But how has a cloud of this size residing close to the Earth been undetected up until now?

Thomas Haworth, a coauthor of the journal and an astrophysicist at Queen Mary University of London, shares some details on this cloud. According to him, “In astronomy, seeing the previously unseen usually means peering deeper with ever more sensitive telescopes — detecting those smaller planets … those more distant galaxies.”

To peer deeper into our atmosphere and discover this new molecular cloud, scientists had to rely on a special instrument. This instrument is a far-ultraviolet spectrograph called FIMS-SPEAR, and it operates as an instrument on STSAT-1, a Korean satellite.

Thanks to this instrument, scientists have been able to spot this molecular cloud that has been hiding in plain sight. Haworth says that this molecular cloud “was pretty much in our cosmic backyard, and we’ve just missed it.”

Here Is What We Know About The Eos Molecular Cloud

First, we know that molecular clouds are made up of gas and dust, which can form hydrogen and carbon monoxide molecules. These clouds can be spotted using radio and infrared observations, which pick up carbon monoxide chemical signals.

However, the Eos molecular cloud was not spotted using carbon monoxide chemical signals since it doesn’t contain many of these signals. But how was the Eos molecular cloud spotted despite not having many carbon monoxide particles?

Haworth says, “The only reason we managed to catch it in this instance is because we’ve been able to look with a different colour of light.” By using the FIMS-SPEAR on the Korean satellite STSAT-1, scientists were able to break down the far-ultraviolet light from the molecular cloud.

Blakesley Burkhart, the lead author of the study on this molecular cloud, also had a few things to say about this cloud. He says that the satellite’s spectrograph was able to show “glowing hydrogen molecules detected via fluorescence in the far ultraviolet.”

This discovery will help scientists to directly measure how molecular clouds are forming and dissociating, and how a galaxy begins to transform interstellar gas and dust into stars and planets,” Burkhart said. Its distance from Earth, at just 300 light-years in comparison with other molecular clouds, which are 1,600 light-years away from Earth, is ideal.
At this distance, scientists will be able to observe this molecular cloud hence understanding the universe’s makeup. Scientists will start researching the Eos molecular cloud to find out more about the formation of planets and stars.