China's FAST telescope finds the enormous atomic cloud.

The world's most enormous atomic cloud, which is twenty times the size of our Milky Way galaxy, was discovered by China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST).

The research, conducted by a multinational team led by Chinese experts, was published in the peer-reviewed scientific journal Nature on Wednesday.

Stephan's Quintet was studied by astronomers using the largest single-dish telescope yet built. These findings demonstrate the existence of a massive low-density gaseous structure located away from the cluster core of Stephan's Quintet.

The hydrogen atoms that make up the atomic cloud stretch for about 2 million light-years. A distance of one light year is approximately 9.46 trillion kilometres.

The most recent discovery supports the idea that gaseous structure is produced due to galaxy interactions. It's been around for a billion years already.

Another implication of the findings was that there could be more extensive low-density atomic gas formations in the universe.

According to lead author Xu Cong of the National Astronomical Observatories of the Chinese Academy of Sciences, "the atomic gas with low density should have been destroyed by the ultraviolet radiation in the cosmic background based on current theories." This finding casts doubt on our current understanding of galaxies' evolution and the universe's gaseous structure.