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A collaborative effort among scientists, led by an astrophysicist from Rutgers University-New Brunswick, has unveiled a potentially star-forming molecular cloud, recognized as one of the largest structures detected in our cosmic vicinity. This cloud ranks among the closest to both the sun and Earth ever found.
The newly identified mass of hydrogen, previously hidden from view, was uncovered by targeting its primary component—molecular hydrogen. This groundbreaking detection marks the first time a molecular cloud has been identified through light emitted in the far-ultraviolet range of the electromagnetic spectrum, paving the way for future investigations using this innovative technique.
The research team has designated the cloud as “Eos,” named after the Greek goddess symbolizing dawn. The findings of this study are detailed in Nature Astronomy.
“This discovery presents fresh opportunities for exploring the molecular universe,” stated Blakesley Burkhart, an associate professor in the Department of Physics and Astronomy at Rutgers School of Arts and Sciences and the leading author of the study. Burkhart also holds a research scientist position at the Center for Computational Astrophysics at the Flatiron Institute in New York.
Molecular clouds consist of gas and dust, predominantly hydrogen, which is crucial for the formation of stars and planets, and essential for sustaining life. These clouds also host other molecules, such as carbon monoxide. Traditionally, molecular clouds have been detected through methods like radio and infrared observations that capture chemical signatures of carbon monoxide.
This recent research harnesses a novel approach to detection.
“This is the inaugural identification of a molecular cloud achieved through direct observation of far-ultraviolet emission from molecular hydrogen,” Burkhart elaborated. “The data illustrated glowing hydrogen molecules detected through fluorescence in the far ultraviolet. This cloud is literally illuminating in the darkness.”
Importantly, Eos does not pose any threat to Earth or the solar system. Its spatial proximity offers a unique chance for scientists to examine the characteristics of a structure within the interstellar medium.
The interstellar medium, comprising gas and dust that fills the void between stars within galaxies, acts as the raw material for new star formation.
“While observing through telescopes, we witness entire solar systems in the process of formation, yet detailed mechanisms of this phenomenon remain elusive,” Burkhart remarked. “The discovery of Eos is thrilling; it allows us to directly analyze how molecular clouds form and dissolve, and how galaxies convert interstellar gas and dust into stars and planets.”
Located roughly 300 light-years from Earth, this crescent-shaped cloud lies on the edge of the Local Bubble, a vast cavity filled with gas surrounding our solar system. Researchers estimate that Eos spans approximately 40 moon diameters across the sky and possesses a mass about 3,400 times that of our sun. Models predict it will gradually dissipate over the next 6 million years.
“Utilizing the far-ultraviolet fluorescence emission technique could significantly enhance our comprehension of the interstellar medium, uncovering hidden clouds throughout the galaxy and extending our reach to the farthest edges of cosmic dawn,” noted Thavisha Dharmawardena, a NASA Hubble Fellow at New York University and co-author of the study.
The team used data from a far-ultraviolet spectrograph, FIMS-SPEAR, which operated onboard the Korean satellite STSAT-1. This spectrograph analyzes far-ultraviolet light emitted by materials, breaking it down into component wavelengths for scientific examination, similar to how a prism works with visible light.
The pertinent data was publicly released in 2023 when Burkhart discovered it.
“It felt as if it was just waiting for us to explore,” she reflected.
The findings underscore the significance of innovative observational methods in deepening our understanding of the cosmos. Burkhart highlighted that although Eos is predominantly made up of molecular hydrogen, it is primarily “CO-dark,” indicating a lack of carbon monoxide and thus eluding traditional detection methods for an extended period.
“The narrative of the cosmos is fundamentally a tale of atomic reconfiguration throughout billions of years,” Burkhart pointed out. “The hydrogen present in the Eos cloud dates back to the Big Bang and subsequently integrated into our galaxy, ultimately coalescing near the sun. It’s been an extensive journey of approximately 13.6 billion years for these hydrogen atoms.”
The discovery was somewhat unexpected.
“During my graduate studies, we were taught that directly observing molecular hydrogen is quite challenging,” Dharmawardena from NYU noted. “It’s astounding that we can visualize this cloud using data we previously didn’t anticipate finding.”
The name Eos also refers to a proposed NASA mission that Burkhart and others are advocating for. This mission seeks to expand the understanding of molecular hydrogen detection across the galaxy, investigating the origins of stars by examining the evolution of molecular clouds.
The research team is diligently analyzing data for molecular hydrogen clouds both nearby and far away. A study recently shared as a preprint on arXiv by Burkhart and collaborators using the James Webb Space Telescope (JWST) suggests they may have identified the most distant molecular gas observed to date.
“By employing JWST, we might have located the farthest hydrogen molecules from the sun,” Burkhart remarked. “Thus, we’ve discovered both some of the nearest and farthest clouds using far-ultraviolet emissions.”
Additionally, the scientific team includes researchers from Technion-Israel Institute of Technology, Queen Mary University of London, University College London, University of Iowa, Korea Astronomy and Space Science Institute, Max Planck Institute for Astronomy, University of Texas at Austin, University of Arizona, University of California, Berkeley, Université Paris Cité, Space Telescope Science Institute, University of British Columbia, Columbia University, and Harvard-Smithsonian Center for Astrophysics.
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