A vast ball of hydrogen, long invisible to scientists, has been discovered just a stone’s throw from Earth.
Located 300 lightyears away and one of the largest single structures ever discovered in the sky, scientists have named the cloud ‘Eos’ after the Greek goddess who personifies the dawn.
The potentially star-forming cloud was discovered by hunting for its main constituent, molecular hydrogen, which can be detected by looking for ultraviolet light.
Scientists estimate that its size on the sky is about the width of 40 Moons and is around 3,400 times more massive than our Sun.
What Eos is, where it’s located
One of the closest molecular clouds to the Sun and Earth ever detected, Eos is crescent-shaped and sits on the edge of the Local Bubble, a gas-filled cavity in space that also encompasses the Solar System.
“This is the first-ever molecular cloud discovered by looking for far-ultraviolet emission of molecular hydrogen directly,” says Blakesley Burkhart, an associate professor at Rutgers University who led the research team
“The data showed glowing hydrogen molecules detected via fluorescence in the far ultraviolet. This cloud is literally glowing in the dark.”
Eos is not dangerous to us on Earth, but rather provides a lab for studying structures within the interstellar medium, the gas and dust that fills the space between stars in a galaxy.
How it was discovered
The far-ultraviolet data was collected by the FIMS-SPEAR instrument installed on Korean satellite STSAT-1.
“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,” says Thavisha Dharmawardena, one of the study’s authors and a NASA Hubble Fellow at New York University.
The abundance of hydrogen – one of the Universe’s most important building blocks – in clouds like Eos also tells scientists about the origins of stars and planets.
Their evolution is a rearrangement of hydrogen atoms that has taken place over billions of years.
The hydrogen that is currently in clouds like Eos existed at the Universe’s dawn, the Big Bang.