Cosmic Tsunami Resurrects 'Dead' Galaxies in Sausage Cluster

Galaxies are often found in clusters, which contain many "red and dead" members that stopped forming stars in the distant past. Now, scientists have discovered that these "comatose" galaxies can be resurrected. If clusters of galaxies merge, a cosmic tsunami can drive the birth of a new generation of stars.

Galaxy clusters consist of groups of galaxies-sometimes thousands-packed together. Over billions of years, these clusters build up structure in the universe, merging with adjacent clusters. When this occurs, there is a huge release of energy as the clusters collide. The resulting shock wave travels through the cluster like a tsunami. Until now, though, scientists had no evidence that the galaxies themselves were affected very much.

In this latest study, the researchers watched the merging galaxy cluster CIZA J2242.8+5301, also known as the Sausage galaxy cluster. They found that the cluster of galaxies was transformed by the shock wave, triggering a new wave of star formation.

"We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role," said Andra Stroe, one of the researchers, in a news release. "The comatose galaxies in the Sausage cluster are coming back to life, with stars forming at a tremendous rate. When we first saw this in the data, we simply couldn't believe what it was telling us."

The new study suggests that the merger of galaxy clusters has a major impact on the formation of stars. The shocks lead to turbulence in the galactic gas, which then trigger an avalanche-like collapse and the formation of very dense, cold gas clouds, which can then form new stars.

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).