Astronomers discover giant star-forming cloud, 5,000 times larger than the Sun, near our solar system

Time of India

08-05-2025

A Rutgers University research team in New Jersey spotted the newly found cloud, which was named Eos—after the Greek deity of dawn. Being only 300 light-years away, it is the closest known big molecular cloud.
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Molecular clouds are huge, cold reservoirs of gas and dust that cradle new stars. What distinguishes Eos is not only its closeness but also its position: it lies on the outer rim of a strange structure called the Local Bubble—a hot, low-density cavity in space that envelops the Sun and a few nearby stars.
Although it looks no more than roughly 40 full moons across in the evening sky, Eos is physically tens of light-years across.
It has a weight greater than 5,000 times the Sun's weight and is, thus, gigantic. All of this would lead one to expect it would be a rich star-forming region—but curiously enough, it contains no evidence of recent star formation.
Why Eos remained undetected in previous sky surveys
Eos was elusive in earlier sky surveys for a straightforward reason: it does not have one of the most important indicators scientists typically search for—carbon monoxide (CO). Carbon monoxide is a tracer molecule that scientists commonly use to find and chart molecular clouds since it produces easily identifiable signals in the infrared and radio regions of the spectrum.
But Eos is unusually lacking in CO, and so is essentially invisible to conventional detection techniques. This has prompted scientists to wonder whether there may be many more clouds like this waiting to be discovered, simply because they lack the molecular "fingerprints" to be detected by previous surveys. Eos could be an intermediate stage in a cloud's life—possibly too young to have been mature enough to form stars or perhaps just too old, with most of its star-forming material dispersed.
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How Eos was discovered using ultraviolet light instead of traditional methods
The real breakthrough of the discovery of Eos lies in the method used to detect it. Instead of relying on traditional CO-tracing methods, the scientists employed ultraviolet (UV) light to identify the cloud. From South Korea's STSAT-1 satellite, which carries the FIMS-SPEAR spectrograph, they identified a far-ultraviolet glow given off by hydrogen molecules in the cloud.
This is the first time a molecular cloud has been detected by far-UV emission.
Hydrogen is the most common element in molecular clouds, but its far-UV signal is typically weak and difficult to detect. The success of this technique could provide an entirely new means of hunting for hidden clouds, especially those without the usual markers such as carbon monoxide.
How Eos helps scientists understand the conditions for star birth
Eos' discovery is not just a curiosity—it's a milestone. Because it's comparatively near the Earth, Eos presents astronomers with a special chance to investigate the early and late phases of molecular cloud life at close proximity.
Although presently no active star formation is observable in it, its dense and cold environment could be an important clue to understanding what conditions precipitate star birth—or suppress it.
In a statement from Rutgers University, according to Professor Blakesley Burkhart, this discovery might open the way for countless additional detections of comparable clouds employing ultraviolet technology. It also stimulates astronomers to reassess suppositions regarding the ways and locations of star births within our galaxy.
NASA mission named after Eos aims to chart far-ultraviolet radiation
The research team now suggests a new space mission by the name of Eos, which is after the cloud. If NASA accepts this mission, it would be aimed at charting far-ultraviolet radiation across the Milky Way to aid astronomers in identifying more molecular clouds that have eluded detection because they do not emit CO.
This mission has the potential to transform our knowledge of the interstellar medium, the enormous gap between stars that is packed with gas, dust, and magnetic fields.
By charting UV emissions on a galactic scale, scientists expect to gain new insights into how molecular clouds such as Eos form, evolve, and give rise to stars and planetary systems.
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