An international team of astronomers led by researchers from the Chinese Academy of Sciences has discovered a giant cloud of low-density atomic hydrogen about 0.6 megaparsecs in size in the Stephan’s Quintet group of galaxies, that is, 20 times larger than our galaxy.
Atomic hydrogen and any cold gas of such low density cannot remain neutral for long in the intergalactic background UV radiation. That is, this cloud of non-ionized gas should seem to be a fresh powerful ejection of some kind of “black hole” … This can also be seen from the shape of the cloud. But there is neither a galaxy nor a “black hole” near the cloud, and the theory of capture and subsequent ejection of matter by “black holes” does not allow the ejection of such an amount of matter by “black holes”. After all, according to the theories, “black holes” cannot lose their matter, they can only throw out some of the matter that falls on them … Therefore, in their conjectures published in the journal Nature, the theorists stated that the cloud was probably formed by tidal forces in the early stages formation of a galactic group. The fact that this is a cloud of non-ionized gas, theorists, according to their custom, called a riddle, that is, just like everything that does not fit into their theory in their other “explanations”, they called paradoxes and errors of nature.
Other hypothetical scenarios for the emergence of this cloud have been invented. For example, the galaxy NGC 7320a, located in the vicinity of Stefan’s Quintet at a distance of 0.3 Mpc from the center (978 thousand light years), passed through the center of the galactic group about 1.5 billion years ago and pulled out a tidal tail of gas from one of the galaxies – members of the Quintet. The same question remains, how has the cloud not ionized in 1.5 billion years? According to another concoction, this structure arose from a high-speed collision between another intruder galaxy and the core of the Quintet. This caused an expanding density wave that pushed the gas outward and formed a giant ring, the diffuse feature being its densest part. The intruder galaxy could be LEDA 141041, which coincides in location with the atomic hydrogen cloud Anon 4, located 0.2 Mpc (652 thousand light years) from the center of the Quintet. It would take about one billion years for it to move to its current position after the collision. The question of the neutrality of the gas of the cloud and this fantasy did not solve without an additional and absolutely unfounded fabrication that the gas was really subjected to ionization, but passed into a neutral phase due to thermal instability.