Cosmic tsunamis can regenerate 'dead' galaxies

The shockwave formed by colliding galaxy clusters can initiate new star formation.
By Kathy Fey | Apr 26, 2015
Astronomers have recently discovered that giant cosmic shockwaves emanating from colliding galaxy clusters are capable of jumpstarting new star generation.

According to a Nature World News report, galaxies are often clustered into groups containing "red and dead" galaxies that stopped forming new stars long ago. Scientists now believe that these "dead" galaxies can be brought back to "life" by colossal cosmic tsunamis.

To uncover this phenomenon, an international team of researchers observed how galaxy clusters can absorb smaller clusters much as a growing city absorbs its suburbs. When galaxy clusters collide during this absorption process, a huge shockwave of energy is created. This shockwave can re-energize the star formation process, causing dormant galaxies to begin producing new stars again.

Scientists from the University of Lisbon and Leiden Observatory came to this conclusion after studying the merging galaxy cluster officially known as CIZA J2242.8+5301 and affectionately known as the "Sausage." The Sausage cluster, located 2.3 billion light-years away, showed evidence of its dormant galaxies coming to life with a new round 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. 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," Andra Stroe of Liden Observatory said in a statement.

The researchers are observing an event that actually unfolded one billion years ago, when the 6-million-mph shockwave spread out from the collision of the clusters. The team believes that the new star formation was instigated by the shockwave's affect on galactic gas.

"Much like a teaspoon stirring a mug of coffee, the shocks lead to turbulence in the galactic gas. These then trigger an avalanche-like collapse, which eventually leads to the formation of very dense, cold gas clouds, which are vital for the formation of new stars," Stroe said.

Despite the vigorous production of new stars in this instance, the team believes that, after the initial effects of the tsunami take place, the galaxies fall to an even deeper state of dormancy than before.

David Sobral of the University of Lisbon explains that "star formation at this rate leads to a lot of massive, short-lived stars coming into being, which explode as supernovae a few million years later. The explosions drive huge amounts of gas out of the galaxies and with most of the rest consumed in star formation, the galaxies soon run out of fuel. If you wait long enough, the cluster mergers make the galaxies even more red and dead they slip back into a coma and have little prospect of a second resurrection."

The study was published in the journal Monthly Notices of the Royal Astronomical Society.

---

Comments
We are dedicated to maintaining a respectful community that actively engages in lively discussions about news stories and blog posts. Please keep the following in mind when writing your comments.