The light of galaxy BRI 1335-0417 is 12.4 billion years old, from when the universe was still extremely young. And yet, the galaxy appears to have a spiral structure in place, adding more complexity to the question of when spiral galaxies like the Milky Way actually formed.
The discovery, reported in Science, is the oldest spiral structure in a galaxy yet. It is estimated that 72 percent of all galaxies are spirals, but this number gets smaller the further back we look. Galaxies are supposed to have started in a messy manner, and over time they ended up more spiral-like.
The discovery of BRI 1335-0417, possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), expands our understanding of what the earliest galaxies in the universe were like. Researchers were surprised to find established structures in even earlier galaxies, but the observations show that this celestial object goes beyond what has been spotted so far.
"I was excited because I had never seen such clear evidence of a rotating disk, spiral structure, and centralized mass structure in a distant galaxy in any previous literature," lead author Takafumi Tsukui, a graduate student at SOKENDAI, said in a statement. "The quality of the ALMA data was so good that I was able to see so much detail that I thought it was a nearby galaxy."
There is also another intriguing fact about BRI 1335-0417: it’s quite big. The team estimates that it is roughly the mass of our own Milky Way, a galaxy that has been accreting gas and gobbling up other smaller galaxies for 13 billion years.
"As BRI 1335-0417 is a very distant object, we might not be able to see the true edge of the galaxy in this observation," comments Tsukui. "For a galaxy that existed in the early Universe, BRI 1335-0417 was a giant."
Galaxies such as this could be the progenitors to the giant elliptical galaxies we observe at the center of galaxy clusters. A major galaxy collision could dramatically change the spiral shape of BRI 1335-0417, or the galaxy could remain a spiral for a very long time, we don't know what the future holds for it.
What we can learn though is something about the Milky Way – and even about our own solar system. There are certainly gaps in what we know about galaxy formation and evolution.
"Our Solar System is located in one of the spiral arms of the Milky Way," added senior author Satoru Iguchi. "Tracing the roots of spiral structure will provide us with clues to the environment in which the Solar System was born. I hope that this research will further advance our understanding of the formation history of galaxies."