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Something is going on in space

Something big is lurking in the vacuum of intergalactic space. It is not a galaxy, although it is of comparable size: a huge cloud of low-gloss hot gas, larger than the Milky Way, in the space between galaxies gathered in huge numbers.

What is even more surprising, did not disperse, but remained collected for hundreds of millions of years.

This not only tells us something new about the environments within the cluster of galaxies, but also suggests a new way of exploring and understanding these colossal structures.

Galactic clusters are, as the name suggests, groups of galaxies that are gravitationally connected. The cluster of galaxies in which our “poor” cloud of gas was found is called Abel 1367, or cluster Leo, about 300 million light-years away. It contains at least 72 major galaxies and forms part of a larger complex of super clusters.

A lot of things often happen in such environments, and astronomers like to peek into them and try to understand how our Universe is connected. In 2017, astronomers using the Japanese Subaru telescope noticed a small warm cloud in Abell in 1367. Since the origin of the clouds was not clear, they returned with more instruments to better study the phenomenon.

The team, led by astronomer Chong Ge of the University of Alabama at Huntsville, used, along with Subaru, ESA’s KSMM-Newton X-Ray Telescope and the Multi Unit Spectroscopic Explorer (MUSE) on the Large Large Telescope (VLT), the world’s largest optical telescope located in Chile. To their surprise, they found that the X-ray emission showed that the cloud was larger than they first thought.

In fact, much larger – larger than the Milky Way galaxy, with a mass about 10 billion times the mass of the Sun. And it didn’t seem to be associated with any known galaxy in the set. It just floated. However, the wealth of data has enabled researchers to measure the temperature of the gas and thus discover traces of its origin.

Cloud temperatures range between 10,000 and 10,000,000 Kelvin, which is in line with the gases found in galaxies, an interstellar medium. The much weaker hot gas in the cluster medium (the space between the galaxies in the cluster) is still hot and amounts to about 100 million Kelvin. This suggests that the gas cloud was removed from the galaxy as it moved through space.

  • It’s like when your hair and clothes fly backwards and run forward against a strong wind. Once removed from the host galaxy, the cloud is initially cold and evaporates in the medium inside the cluster, like melting ice in summer – explained the physicist of the University of Alabama Ming Sun.

This is fascinating, but strange because researchers could not find any nearby galaxy that could explain that it happened recently. Yet, if gas was torn out of its galaxy hundreds of millions of years ago, as this lack of proximity suggests, how come it did not spread in the internal cluster medium?

To solve this, the team performed calculations and discovered that the magnetic field can hold a gas cloud for a longer period of time despite instabilities that would otherwise break it.

Given the large mass of clouds, the team of scientists concluded that the parent galaxy from which it was torn is large and massive. This could help them figure out which galaxy it is. Another clue could be traces of gas propagating from the clouds and which could be directed in the right direction.

In addition, now that one lone cloud has been identified, scientists have a set of data to help identify other such clouds in the future. This will provide valuable information about the dynamics within the cluster and the distribution of matter in the galactic clusters.

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