A Cloud That Glows In The Dark Has Been Discovered Near Earth
An enormous molecular cloud has been discovered near Earth, surprising astronomers. It was named Eos, after the Greek goddess of dawn.
The newfound cloud is shaped like a crescent and made of hydrogen gas. It is located 300 light-years from Earth, making it the closest known molecular cloud.
At about 100 light-years wide, it is one of the largest structures in the sky. To put it to scale, it is equivalent to 40 moons lined up side by side.
“It’s huge, and it’s been hidden for this whole time,” said Blakesley Burkhart, the leader of the discovery and an associate professor in the Department of Physics and Astronomy at Rutgers University in New Jersey.
Despite its massive size and relative closeness to Earth, Eos has managed to escape detection due to its low content of carbon monoxide, which astronomers usually rely on to identify molecular clouds.
Instead, the researchers spotted Eos because of the fluorescent glow of its hydrogen molecules. This approach could reveal many more clouds hidden throughout the galaxy.
The most common substance in the universe is molecular hydrogen. By discovering and analyzing hydrogen-filled clouds like Eos, astronomers could detect previously unknown hydrogen reservoirs and come up with a more accurate estimation of how much hydrogen there is for the formation of stars and planets across the universe.
While analyzing 20-year-old data from a spectrograph on the Korean Science and Technology Satellite-1, Burkhart stumbled upon Eos. The satellite was launched into space in 2003 to track the spread of hot gas in the Milky Way.
The spectrograph broke down far-ultraviolet light into a spectrum of wavelengths so that scientists could identify emissions from different molecules.
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In one part of the sky that appeared to be empty, hydrogen molecules revealed Eos to be glowing in the dark.
Through interactions with the North Polar Spur, a gigantic region of ionized gas that stretches from the plane of the Milky Way to the northern celestial pole, Eos has developed a crescent shape. It lines up perfectly with the North Polar Spur at high latitudes.
The alignment indicates that the energy and radiation from the North Polar Spur were driven by stellar winds or past supernovas, influencing Eos and other surrounding gas. Simulations that traced Eos’ evolution suggest that it will evaporate in roughly six million years.
The cloud does not seem to have gone through any bursts of star formation in the past, but it is unclear whether the cloud will start forming stars before it vanishes.
Burkhart and colleagues are currently developing a mission concept for a NASA spacecraft named after the molecular cloud. It would measure the molecular hydrogen content in clouds across the Milky Way.
The new study was published in the journal Nature Astronomy.
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