Two galactic megamergers discovered unfolding in the early universe
Astronomers have discovered two enormous clusters of ancient galaxies that existed just 1.5 billion years after the creation of the universe in the Big Bang. According to current theoretical computer models of the early universe, clusters this size should not have come into existence until the cosmos was around three billion years old, leaving astronomers puzzled as to how the newly discovered specimens grew so large, so fast.
The protoclusters, designated SPT2349-56 and the Dusty Red Core (DRC), were first identified by the South Pole Telescope and the Herschel Space Observatory. Roughly 90 percent of the known universe separated the galaxy clusters from the watching telescopes, causing them to appear as little more than smudges of light.
High-resolution follow-up observations from the Atacama Large millimetre/submillimetre Array (ALMA) and the Atacama Pathfinder Experiment (APEX), both of which are located in Chile, revealed the truly colossal nature of the discovery. Based on the new data, SPT2349-56 is currently estimated to be comprised of 14 enormous galaxies, while the (relatively) smaller DRC is made up of 10.
DRC was named for the light emitted by the dusty red galaxies that compose the grouping. Ordinarily, the material contained within this type of galaxy would be used up very quickly in the creation of new stars, giving it a relatively short lifespan. Therefore, the discovery of so many dusty red starburst galaxies located in the same place at the same time came as a surprise to the astronomers.
In a paper published today in the journal Nature, astronomers concluded that each of SPT2349-56's galaxies were forming new stars about 50 – 1,000 times faster than the Milky Way. SPT2349-56 is now the most active star formation region ever detected in the early universe.
"These discoveries by ALMA are only the tip of the iceberg. Additional observations with the APEX telescope show that the real number of star-forming galaxies is likely even three times higher," states ESO astronomer Carlos De Breuck. "Ongoing observations with the MUSE instrument on ESO's VLT are also identifying additional galaxies."
Light travels at an astonishing pace of roughly 300,000 km/s (186,000 mi/s), yet it can still take millions, if not billions of years to reach Earth from the point it leaves its source. Because of this, a telescope never views its target as it is in the present day, but rather gazes back through time, to view it at the point that it first emitted the light.
In the case of SPT2349-56, the light left its constituent galaxies when the universe was just one tenth its current age. At this point, both groups were on the verge of descending into chaos, with the galaxies destined to smash into one another with incredible violence, and, eventually, merge to form the cores around which vast galaxy clusters would form.
By observing these relic protoclusters, and feeding that data into advanced computer simulations, astronomers can better understand the nature of the early universe, and how it may have evolved into its current state.
Scroll down to watch an artist's impression video of a group of galaxies interacting and merging in the early universe.