Scientists have discovered a gigantic trail of gas from a quintet of warring galaxies. The mysterious gas cloud – the largest ever seen around a group of galaxies – may have been left behind by a ‘cosmic intruder’, a new study reveals.
The cloud – an unexplained stream of hydrogen gas 2 million light-years away from the galactic group known as Stephan’s Quintet – was discovered in the deepest-ever scan of the region by the spherical telescope at opening of five hundred meters (FAST) in China. Researchers believe that the gas trail,, could be “tidal debris” formed after the whirlpool galaxies collided with a large cosmic intruder about 1 billion years ago.
Named after its 19th century discoverer, French astronomer Édouard Stephan, the Stephan Quintet is a group of five galaxies that are “locked in a cosmic dance of repeated close encounters”, according to NASA, as they orbit and constantly pirouette against each other. Located about 300 million light-years from Earth, the quintet is the first group of compact galaxies ever spotted and has been imaged by numerous telescopes, including the Hubble Space Telescope and the James Webb Space Telescope. Now, new research, conducted with FAST and published October 19 in the journal Nature (opens in a new tab)has peered 100 times deeper into the group of galaxies than ever before, revealing the huge cloud of gas emanating from it.
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“This is the largest atomic gas structure ever found around a group of galaxies,” Xu Congthe study’s lead author and an astronomer from the National Astronomical Observatories of the Chinese Academy of Sciences, said in a statement.
The gas cloud formed about 1.5 billion years ago, when an unknown interaction extracted atomic hydrogen from galaxies and pulverized it. Researchers blame one or more fast-moving galaxies for colliding with the quintet, and they’ve even identified a possible culprit – galaxy NGC 7320a, which is currently speeding through the cosmos at nearly 15 million mph (24 million km). /h).
“A hypothetical scenario for the formation of the diffuse feature is that NGC 7320a…passed through Stephan’s Quintet about 1.5 billion years ago…and extracted from one of the central member galaxies from Stephan’s Quintet a tidal tail, which developed into the diffuse entity we now see,” the astronomers wrote in the study.
Alternatively, the gas cloud could have been stirred up by a head-on collision between one of the quintet galaxies and another traveling galaxy, such as the Anon 4 galaxy. A head-on collision would have created a shock wave that pushed the hydrogen towards the outside. in an expanding halo around the group, the researchers wrote. Another possibility is that the contrail did not come from a galactic collision at all, but from the remnants of the primordial gas cloud from which one or more of the quintet galaxies formed.
Regardless of the cause of the trail, scientists also don’t know how the gas lingered for so long. Astronomers don’t generally expect gas clouds to survive more than 500 million years, because exposure to ultraviolet radiation from stars tends to ionize them until they collapse. dissipate. The researchers believe the low-density cloud may leak energy absorbed by stars in its surroundings, but understanding how this would happen requires further study. The answer could provide insight into the birth and growth of galaxies.
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