Stars and planets are born in swirling clouds of cosmic gases and dust that fill hydrogen and other molecular components. On Monday, astronomers revealed the discovery of the closest known cloud to Earth, a huge, crescent-shaped mass of star-forming possibilities.
It was discovered that the clouds lurk around 300 light years from the solar system, after the Greek goddess of dawn, named EOS. It is the first molecular cloud to be detected using hydrogen fluorescence, according to Blakeley Burkhart, an astrophysicist at Rutgers University.
“If you see these clouds in the sky, it's huge,” said Dr. Burkhart, who published his discovery with a colleague in Journal Nature Astronomy. And, “It literally shines in the darkness,” she added.
Identifying and studying clouds like EO, particularly based on hydrogen content, could reconstruct astronomers' understandings of how much material within the galaxy can be used to produce planets and stars. It also helps to measure the creation and destruction rate of fuel that can drive such formations.
“For the first time, we are seeing this hidden reservoir of hydrogen that can form stars,” said Thavisha Dharmawardena, an astronomer at New York University, who is the author of the study. After EOS, astronomers said they “want to find more” such hydrogen-rich clouds.
Molecular hydrogen, made up of two hydrogen atoms, is the most abundant material in the universe. The stellar nursery clogs it. However, it is difficult to detect molecules from the ground because they shine at a far-wave wavelength that is easily absorbed by the Earth's atmosphere.
The easiest to find is carbon monoxide, a molecule made up of one carbon atom and one oxygen atom. Carbon monoxide emits light at longer wavelengths than can be detected at radio observatory on the Earth's surface, a more common technique for identifying star-forming clouds.
EOS avoided detection for a very long time, because it was surprising and there was very little carbon monoxide.
Dr. Burkhart noticed the cloud while studying data from about 20 years ago from the Far-Ultraviolet Imaging Spectrograph or FIMS, an instrument riding a Korean space satellite. She found the structure of molecular hydrogen data in spatial domains that she believes there is no molecular cloud, and worked with Dr. Dharma Wardenna to further investigate.
“At this point, I knew almost every molecular cloud by name,” Dr. Dharmawardena said. “I had no idea about this structure. I couldn't put it.”
Dr. Dharmawardena cross-checked the discoveries in our galaxy's interstellar dust 3D map. These maps were constructed with data from the recently retired Gaia Space Telescope. The EOS was “very clearly outlined and visible,” she said. “This gorgeous structure.”
John Black, an astronomer at Sweden's Chalmers Institute of Technology, praised the techniques used to reveal EOS because he was not involved in the work.
“It's really great to be able to see molecular hydrogen in person and track the outline of this cloud,” Dr. Black said. Compared to carbon monoxide, hydrogen shows the “true picture of shape and size” of EOS, he added.
Using molecular hydrogen content, astronomers estimated the mass of EO to be about 3,400 times the mass of our Sun. This is much higher than the estimated value calculated from the amount of carbon monoxide present in the clouds – 20 times the mass of our sun.
Similar measurements of carbon monoxide may underestimate the mass of other molecular clouds, Dr. Burkhart said. She added that it has important significance in star formation as large clouds form larger stars.
A follow-up study of EOS, which has not yet been peer-reviewed, found that the cloud had not formed a star in the past. However, the question remains whether or not they will start creating stars in the future.
Dr. Burkhart worked with a team of astronomers to conceptualize the NASA spacecraft called EOS, which inspired the newly discovered Cloud's name. The proposed space telescope can map the molecular hydrogen content of clouds across the galaxy, including its same name.
Perhaps such a mission will fix knowledge of the ability of more hidden clouds and known stellar mists to combine with stars and planets.
“I really don't know how stars and planets form,” Dr. Burkhart said. “If we can see molecular hydrogen in person, we can see how the birthplace of the stars is formed and how they are destroyed.”
