Astronomers have made a discovery of cosmic proportions: they have seen the beginning stages of a massive galaxy's formation. Their findings, detailed this week in a paper published in the journal Nature, confirmed something astronomers had theorized about but had never seen an example of: that galaxies in the early universe had a highly dense core formation phase, which allowed them to house billions of stars in relatively compact spaces.
Using high-powered telescopes and cameras, researchers observed a newly discovered galaxy -- which they nicknamed "Sparky" -- as it was about 11 billion years ago. That's roughly three billion years after the Big Bang. To see Sparky is to get a sense of what it looked like when galaxies formed during the earliest stages of the universe's existence.
"It was really a crazy time in galaxy formation. The universe was very extreme, forming these incredibly dense galaxies and it was forming them really, really rapidly," said Yale University's Erica Nelson, the lead author on the paper. "It's fascinating that the early universe could make galaxies in this way and the modern universe just can't anymore, and we’re really beginning to understand in a profound way how different the early universe was than it is now."
The early universe was a much more dense place, since matter has been expanding away from each other ever since the Big Bang. At the time astronomers spotted Sparky -- when it had a “violent, turbulent-star producing environment" -- the galaxy was jam-packed with about 300 billion stars, Nelson said. That's twice as many stars as in our home galaxy, the Milky Way, and in a fraction of the space. Researchers think that Sparky continued rapidly producing stars but stopped about 10 billion years ago, when it expanded and eventually ate smaller galaxies as it grew.
Since the mid-2000s, astronomers have been on the hunt for an example of a giant elliptical galaxy forming, Nelson said. Technological advances, particularly with the placement of a new camera on the Hubble Space Telescope in 2009, have helped their quest. “Understanding how these galaxies were formed is to understand how we got here and how it is that we exist,” Nelson said. “This is understanding our greater human history.”