UCT astronomers discover first dark cloud without host galaxy

Astronomers at the University of Cape Town (UCT) have discovered a mysterious chain of hydrogen gas clouds.

The dark clouds are the size of a massive galaxy and were discovered through the South African MeerKAT telescope, which the scientists say is proving to be a ground-breaking device in their five-year project to understand galaxy distribution and evolution.

The astronomers say it is the first time they have seen such a massive gas cloud without a “host” galaxy.

“The hydrogen is the fuel for star formation, and so where you have a lot of hydrogen, amassed into a dense object, you have stars or a galaxy of stars, so it is quite a discovery,” said professor Thomas Jarrett from UCT’s astronomy department

He said he and his team were going to conduct further studies because such discoveries always lead to a new understanding of nature. The discovery could also provide new insights about galaxy evolution.

The astronomers’ next move is to figure out how this cloud came to be, and where it is headed.

“It could be the detritus from a titanic collision between two galaxies, stripping and separating the gas from the stars. But we really don’t see the progenitors, the two or more galaxies that did this. They could be there, just hiding somehow,” Jarrett said. 

“Alternatively, it could be more pristine gas that has been flowing through the filament of the cosmic web, into the ‘attractor’ that it appears to be aimed.
“This gravitational attractor is a massive galaxy group. We need deeper MeerKAT observations, and a deeper optical imaging to dig down into the fainter stuff to see if we can discern any gas or star ‘trails’ that point to a past tidal disturbance,” he added.

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Marcia Zali
Marcia Zali is an award winning journalist

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