Do they mean molecular cloud? I've never heard about atomic clouds. (Yes I know what atoms and molecules are. Molecular cloud has a specific meaning, and consequences, in astrophysics. :)

They mean atomic hydrogen (HI) gas structure and call it a cloud despite its huge scale. The article shows the huge diffuse HI structure around a distant galaxy cluster.

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That's the word the researcher uses in an interview. The article doesn't specifically say whether its an English quote or translation.

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This is a great find. There have been some great finds lately, love to see it!

So these are proto-galaxy clouds we think? Massive cloud of just hydrogen, like what was present early after the Big Bang? That could collapse to start and build young massive stars?

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>An international team led by Chinese scientists has discovered the biggest atomic cloud in the universe – a surprising finding that could help researchers better understand the origins of galaxies.

>The cloud, made up of hydrogen atoms, measures about 2 million light years across and is 20 times larger than our Milky Way galaxy[...]

First and partial 2nd paragraph from the linked article.

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Yes I read the article. It doesn’t answer my questions.

"So these are proto-galaxy clouds we think?"

>a surprising finding that could help researchers better understand the origins of galaxies.

"Massive cloud of just hydrogen, like what was present early after the Big Bang?"

>The cloud, made up of hydrogen atoms

"That could collapse to start and build young massive stars?"

>Their unexpected discovery will support numerical simulations to explain how Stephan’s Quintet formed

Was just trying to help... The last one is talking about origin of galaxies, but the cloud isn't nearly dense enough to be forming stars. If you have other questions that were not answered in the article, you did not list them here.

Thank you! Was just trying to make sure I understood what they were saying. This is really neat

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They wrote in their nature article that the ‘cloud’ is either from tidal interactions between existing members in the galaxy group or from another galaxy approaching the galaxy group. Both explanations deal with extended diffuse atomic hydrogen from existing systems increasing in density from tidal interactions between galaxy group members and/or interactions with an external galaxy well after the Big Bang.

So not a protogalaxy cloud as you described. Most likely existing HI gas from members or another incoming galaxy.

>we carried out deep mapping observations of the 21 cm H i emission over a region of around 30′ × 30′ centred on SQ. ... Here we report atomic hydrogen (H i) observations in the vicinity of SQ with a smoothed sensitivity of 1σ = 4.2 × 1016 cm−2 per channel.

https://www.nature.com/articles/s41586-022-05206-x I searched the original paper and they don't have any discussion regarding molecular hydrogen. It is also extremely hard to directly detect molecular hydrogen as far as I know.

FAST is increasingly making some new discoveries in space.