The wonders of the universe are vast and still need to be discovered, but while we imagine that the mysteries that await us are thousands of light years away, the reality is that some of them are closer than we might think and we just did not see it. One of these close mysteries is a cloud of gas so gigantic it would take the place of 40 full moons if it were visible to the naked eye just 300 light-years from Earth, in the immediate vicinity of our solar system.
The thing is, we have seen harder to detect things that were farther away before, so the fact that this gas cloud was right beside the Milky Way and perfectly poised to be seen is even more surprising. The person responsible for the discovery is astrophysicist Blakesley Burkhart and her team, who published their results in Nature Astronomy.
The gas cloud that could change our perception of the universe
Why is this discovery so fascinating? Well, this molecular cloud is invisible to traditional methods because it barely emits any carbon monoxide, which is what telescopes normally look for. Instead, it was detected by the fluorescence of molecular hydrogen in the far ultraviolet, a far more advanced technique.
But still, considering its size, it should have been detected before, as Eos is located within what is known as the Local Bubble, a region of space where our solar system resides and is characterized by a low density of matter due to ancient supernova explosions. Even there, Eos stands out for its estimated mass of about 3,400 solar masses of molecular hydrogen (H₂) and a diameter of approximately 25.5 parsecs. And yet, it remained relatively invisible due to the fact that Eos has very little detectable CO, making it a “dark” molecular cloud.
Since gas clouds have been known for their ability to form new stars, one of the key questions raised by this finding is whether Eos, has the potential to eventually give rise to new stars considering its peculiar levels of CO. Researchers assessed this by applying the Jeans mass criteria, which is a method used to determine if a cloud has sufficient mass to collapse under its own gravity. Their results suggest that, at temperatures above 100 K, the cloud remains on the edge of stability, meaning that star formation is unlikely in the near future, though not entirely out of the question and it would have nothing to do with the CO levels detected, but with other external factors.
The analysis also highlights that Eos is under intense exposure to ultraviolet and X-ray radiation from its surroundings and it is causing a rapid breakdown of molecular hydrogen (H₂), outpacing its regeneration. As a result, the cloud is gradually dispersing, with scientists estimating it will fully dissipate in roughly 5.7 million years, which is not long in relative terms and will likely eliminate the possibility of a new star having time to appear.
But the importance of these findings go well beyond just Eos, they suggests that other similar molecular clouds could be hidden from conventional observation and may also be present in nearby regions of space. The use of far-ultraviolet fluorescence has proven crucial in uncovering Eos and may become a vital technique in detecting more of these elusive structures within the interstellar medium.
Additionally, observing Eos as it dissipates offers a valuable opportunity to examine why star formation is often inefficient. Researchers noted that the rate at which radiation breaks down molecular hydrogen is about three times higher than the local star formation rate, a pattern that supports recent models explaining why galaxies form stars from gas at such a limited pace.