The birth of stars begins in large, cold clouds of gas and dust that eventually collapse under the influence of gravity. Molecular clouds are vast cosmic formations that often stretch hundreds of light-years away, and scientists have just discovered a massive cloud hiding in our celestial neighborhood.
The cloud, named Eos after the Greek goddess of the dawn, was discovered at a distance of about 300 light-years from our solar system. According to an article published this week in the journal Nature Astronomy, it is one of the largest single structures in the sky and possibly the closest molecular cloud to Earth. Because it is so close, it gives astronomers a unique opportunity to observe the process of star formation and the molecular universe from the front row.
The stellar nurseries in our shared galactic neighborhood lie along the surface of the Local Bubble, a large hot cavity of plasma surrounded by a shell of gas and dust. To find molecular clouds inside this bubble, scientists have had to rely on observations of dust emissions. For the recent discovery, however, the scientists found a nearby molecular cloud by detecting the fluorescent nature of hydrogen in the far ultraviolet region of the electromagnetic spectrum, the article says.
“This is the first-ever molecular cloud detected by directly searching for the far ultraviolet emission of molecular hydrogen,” Blakeslee Burkhart, a professor of physics and astronomy in Rutgers’ School of Arts and Sciences and lead author of the study, said in a statement.
Molecular hydrogen, which is made up of two hydrogen atoms cross-linked together, is the most abundant molecule in the universe. However, it is also difficult to detect because it glows in the far ultraviolet range, which is absorbed by the Earth’s atmosphere. “The data showed that the hydrogen molecules that glow can be detected by fluorescence in the far ultraviolet,” Burkhart adds. “This cloud literally glows in the dark.”
In addition to glowing, Eos is shaped like a crescent moon and is located at the edge of the Local Bubble. Its apparent size is equal to 40 full moons in the sky, and its mass is about 3400 times that of the Sun. Using the same technique that revealed this previously invisible cloud, scientists may discover more hidden clouds across the Milky Way galaxy.
“When we look through our telescopes, we see entire solar systems in the process of forming, but we don’t know the details of how that happens,” says Burkhart. “Our discovery of Eos is exciting because we can now directly measure how molecular clouds form and separate, and how a galaxy begins to transform interstellar gas and dust into stars and planets.”
