Galaxies are usually composed of atomic gas. SciTechDaily notes that the evolutionary process of galaxies usually involves the accumulation of atomic gas from the intergalactic middle and the creation of stars out of such gas.
Thus, because of atomic gas' cruciality when it comes to the evolution and formation of galaxies, scientists give intense focus on the research and observation of these intergalactic gasses.
The most direct method of digging into atomic gas is to observe the atomic hydrogen structure line that is worth 21cm within the radio wavelength sets.
Huge Cloud of Atomic Gas Observed
With the help of the Five Hundred Meter Aperture Spherical Telescope (FAST), a researcher of the NAOC or National Astronomical Observatories of the Chinese Academy of Science found a huge cloud of atomic gas.
This was discovered through in-depth observations and mapping of this line emission worth 21cm. It was specifically noted in Stephan's Quintet, where five galaxies are closely located to each other, as noted by NASA.
In Stephan's Quintet, there is one galaxy that is proximate to earth while the other four maintain interaction with each other.
The researcher observed that the cloud had an estimated length of around 2,000,000 light years. These findings make the cloud's size to be 20 times that of the Milky Way's.
Among other radio telescopes that are single-dish, FAST has the greatest sensitivity and largest size. Aside from that, FAST is armed with a receiver that has 19 beams which is considered the biggest L-band feed arrays with multiple beams for observations within the 21cm line.
The FAST receiver's commissioning led to a new door to examine atomic gas across the universe, especially for gasses that are distant and have low density.
Such findings were recently included in the Nature journal.
Biggest Atomic Gas Cloud Observed Within a Group of Galaxies
Xu Cong, the researcher behind this discovery, noted that this cloud of atomic gas was the biggest observed within a group of galaxies.
According to SciTechDaily, the particular observation attained a remarkable sensitivity level. This heightened sensitivity marked it as the most sensitive atomic hydrogen observation in the line emission with an angular resolution of 4'.
This discovery relays that gas with a huge scope, that is diffused, and that has low density exists in a location that is distant from the group's center. SciTechDaily also reports the likelihood that such gas has been present for around a billion years.
These observations have the capacity to challenge what is already known and established about the formation and evolution of galaxies. This is because there is a lack of clarity pertaining to how atomic gas with low density can endure ionization brought about by intergalactic ultraviolet background radiation for remarkably long periods.
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