The detection of the celestial body by international team of scientists could redefine understanding of interstellar medium.
(Nanowerk News) An international team of scientists has discovered a potentially star-forming cloud that is one of the largest single structures in the sky and among the closest to the sun and Earth ever to be detected.
The scientists have named the molecular hydrogen cloud “Eos,” after the Greek goddess of mythology who is the personification of dawn. Their discovery, outlined in a study published in Nature Astronomy (“A nearby dark molecular cloud in the Local Bubble revealed via H2 fluorescence”), stems from an innovative analytical method.
This vast ball of hydrogen, long invisible to scientists, was revealed by looking for its main constituent—molecular hydrogen. The finding marks the first time a molecular cloud has been detected with light emitted in the far-ultraviolet realm of the electromagnetic spectrum and points the way to further explorations using the approach.
This video illustrates the place of Eos—a newly discovered molecular hydrogen cloud that is 99-percent CO dark—on the edge of the Local Bubble, a large gas-filled cavity that encompasses the solar system. It is the nearest molecular cloud to earth at only 300 light years away. Scientists estimate that Eos is vast in projection on the sky, measuring about 40 moons across the sky, with a mass about 5,400 times that of the sun. (Video): Thomas Müller, Max Planck Institute for Astronomy, and Thavisha Dharmawardena, New York University)
“This opens up new possibilities for studying the molecular universe,” says Blakesley Burkhart, an associate professor in Rutgers University-New Brunswick’s Department of Physics and Astronomy, who led the team and is an author of the study.
Molecular clouds are composed of gas and dust—with the most common molecule being hydrogen, the fundamental building block of stars and planets and essential for life. They also contain other molecules, such as carbon monoxide (CO). Molecular clouds are often detected using conventional methods such as radio and infrared observations that easily pick up the chemical signature for carbon monoxide.
“Traditional methods, such as mapping through the presence of carbon monoxide, didn’t reveal the cloud’s full extent,” adds Thavisha Dharmawardena, a NASA Hubble Fellow at New York University and one of the study’s lead authors. “Eos is 99-percent ‘CO-dark,’ meaning that we can not trace it with conventional survey methods, which primarily use CO, leading Eos to be hidden in plain sight all this time.”
For this work, the scientists, who included Andrew Gordon Wilson, an associate professor at NYU’s Courant Institute of Mathematical Sciences, employed a different approach.
“This is the first-ever molecular cloud discovered by looking for far ultraviolet emission of molecular hydrogen directly,” notes Burkhart, also a research scientist at the Flatiron Institute’s Center for Computational Astrophysics. “The data showed glowing hydrogen molecules detected via fluorescence in the far ultraviolet. This cloud is literally glowing in the dark.”
“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,” adds Dharmawardena.
While Eos poses no danger to Earth and the solar system, the proximity of this gas cloud presents a unique opportunity to study the properties of a structure within the interstellar medium, scientists note.
The interstellar medium, made of gas and dust that fills the space between stars within a galaxy, serves as raw material for new star formation.
“When we look through our telescopes, we catch whole solar systems in the act of forming, but we don’t know in detail how that happens,” Burkhart explains. “Our discovery of Eos is exciting because we can now directly measure how molecular clouds are forming and dissociating, and how a galaxy begins to transform interstellar gas and dust into stars and planets.”
The crescent-shaped gas cloud is located about 300 light years away from Earth. It sits on the edge of the Local Bubble, a large gas-filled cavity in space that encompasses the solar system. Scientists estimate that Eos is vast in projection on the sky, measuring about 40 moons across the sky, with a mass about 5,400 times that of the sun. The team used models to show it is expected to evaporate in 6 million years.
The above video illustrates Eos’s place within the Local Bubble (Credit: Thomas Müller, Max Planck Institute for Astronomy, and Thavisha Dharmawardena, New York University).
Eos was revealed to the team in data collected by a far-ultraviolet spectrograph called FIMS-SPEAR (an acronym for fluorescent imaging spectrograph) that operated as an instrument on the Korean satellite STSAT-1. A far-ultraviolet spectrograph breaks down far-ultraviolet light emitted by a material into its component wavelengths, just as a prism does with visible light, creating a spectrum that scientists can analyze.
