Milky Way like galaxy?
A very long time ago, in the very early Universe, scientists have discovered a galaxy that seems way too advanced to have grown in the short timespan since the Big Bang. It's called SPT0418-47, and it's lurking 12.4 billion light-years away - when the Universe was just 1.4 billion years old.
What makes it special are the similarities to our own galaxy, the Milky Way. Although it lacks the characteristic curving arms of a spiral galaxy, SPT0418-47 does consist of a flat, rotating disc. It has a similar mass to the Milky Way. And, even more stunningly, it has a galactic bulge, the tightly packed concentration of stars found in the middle of most spiral galaxies.
Although earlier rotating disc galaxies have been found, SPT0418-47 is the earliest we've found that has a galactic bulge, adding to a growing body of evidence that galaxies form and evolve quite differently from how we thought they did.
"This result represents a breakthrough in the field of galaxy formation, showing that the structures that we observe in nearby spiral galaxies and in our Milky Way were already in place 12 billion years ago," said astrophysicist Francesca Rizzo of the Max Planck Institute for Astrophysics in Germany.
Back in the Universe's infancy, everything was a lot messier than it was today (not to be confused with Messier objects). Galaxies tended to be hot and blobby, with stars chaotically orbiting any which way - likely, astronomers believe, because they were colliding with each other.
In a new study, published in the journal Nature on Wednesday, observations made by Chile's Atacama Large Millimeter/submillimeter Array (ALMA) of SPT–S J041839–4751.9, or SPT0418-47 for short, show the infant galaxy has features similar to those of our own more mature Milky Way. Light from the galaxy took 12 billion years to reach us. That means astronomers are looking back in time at a galaxy that formed less than 1.5 billion years after the birth of the universe.
Previous modeling and observations have led astronomers to theorize that the period after the universe's birth was tumultuous. Early galaxies were likely smashing into each other and merging to form big, disordered masses of stars. They shouldn't settle down into neat, flat disks. But SPT0418-47 does, and that's quite a surprise that upends some of our beliefs about early cosmic activities in the universe.
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