Two cutting-edge telescopes have been used to take a look at the furthest reaches of the universe and in doing so have discovered a cosmic collision of epic proportions. When the universe was just 10 percent of its current age, 14 galaxies ended up smashing into each other, creating a megamerger. The details are published in Nature.
This prodigious pile-up is made up of starburst galaxies, which are producing so many stars in a such a (relatively) small volume of space that it makes this region the most active one ever observed in the early universe. Each one of these galaxies produces stars between 50 and 1,000 times more quickly than our own Milky Way.
The system, named SPT2349-56, is considered a protocluster, with the merger happening 1.5 billion years after the Big Bang. As these galaxies merge, they are going to form a single massive galaxy likely the progenitor of the central cluster galaxies we see in the universe today.
"How this assembly of galaxies got so big so fast is a mystery. It wasn’t built up gradually over billions of years, as astronomers might expect," lead author Tim Miller of Yale University said in a statement. "This discovery provides a great opportunity to study how massive galaxies came together to build enormous galaxy clusters."
The team combined the extraordinary capabilities of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX) to discover this megamerger. As it turns out, it is not a unique object. A different team also used the instruments and discovered a 10-way merger of dusty star-forming galaxies, as reported in the Astrophysical Journal.
“The lifetime of dusty starbursts is thought to be relatively short, because they consume their gas at an extraordinary rate," Iván Oteo, lead author of the second study, added. "At any time, in any corner of the Universe, these galaxies are usually in the minority. So, finding numerous dusty starbursts shining at the same time like this is very puzzling, and something that we still need to understand."
The galaxies were first spotted as very faint objects by instruments such as the South Pole Telescope and the European Space Agency’s observatory Herschel. Subsequent observations revealed that the light blotches were not single galaxies but actually two megamergers with many members.
"These discoveries by ALMA are only the tip of the iceberg," comments Carlos De Breuck, an astronomer for the European Southern Observatory. "Additional observations with the APEX telescope show that the real number of star-forming galaxies is likely even three times higher."
The early universe continues to be full of unknowns but we are finally (and literally) seeing some light in the dark.