What were galaxies like when they were born in the early Universe? Astronomers are having to re-think their assumptions after the discovery of a very distant, very young galaxy that looks surprisingly like our own mature Milky Way galaxy.
To see young galaxies astronomers use ever-bigger, more powerful telescopes that can look further into the past when “baby” galaxies were just beginning to develop.
It was assumed that spiral galaxies with central bulges of stars, like the Milky Way, are mature structures, and that any attempt to see young galaxies still in the process of forming would show only chaos that bears no resemblance to the Milky Way.
A new discovery might change that—the most well-ordered galaxy disc ever observed in the early Universe.
What is the ‘ring of light’ galaxy?
Galaxy SPT0418-47 is 12 billion light years away, which means that its light—just captured using radio telescopes in Chile—has taken 12 billion years to arrive.
That image, above, is of galaxy SPT0418-47 12 billion years ago when, crucially, the Universe was just 1.4 billion years old.Recommended For You
Why does it look like a ‘ring of light?’
Its similarity to the Milky Way is inferred; what the astronomers actually captured—using the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner—was an image of galaxy SPT0418-47 being “gravitationally lensed.”
What is gravitational lensing?
Perfect for studying far-off and faint galaxies, gravitational lensing is when the gravitational pull from a closer, but aligned galaxy distorts and bends the light from a distant galaxy, causing it to appear misshapen and magnified.
It essentially acts as a powerful magnifying glass, though the resulting image is of a “ring of light” around the nearby galaxy.
What this research has done is debut a new computer modeling technique to tease-out the distant galaxy’s true shape, and the motion of its gas, from that “ring of light.”
What is galaxy SPT0418-47 like?
“When I first saw the reconstructed image of SPT0418-47 I could not believe it: a treasure chest was opening,” said Francesca Rizzo, PhD student from the Max Planck Institute for Astrophysics in Germany, who led the research published last week in Nature.
SPT0418-47 is, surprisingly, not a place of chaos, turbulence and instability. After reconstructing the galaxy’s true shape and the motion of its gas using a new computer modeling technique, the researchers discovered that SPT0418-47 is a disc galaxy with a central bulge of stars packed tightly around the galactic center—just like the Milky Way.
That’s a feature not seen before in the distant Universe.
It’s also got material in it that rotates around the center. It has no spiral arms, like the Milky Way (in fact, it will one day become an elliptical galaxy), but in these other ways it’s something of a Milky Way look-a-like.
How important is this discovery?
“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 Rizzo.
“The big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations,” said co-author Filippo Fraternali from the Kapteyn Astronomical Institute, University of Groningen in the Netherlands.
Why are the researchers puzzled?
SPT0418-47 just shouldn’t be so well-ordered and mature-looking—it’s way too young.
“What we found was quite puzzling; despite forming stars at a high rate, and therefore being the site of highly energetic processes, SPT0418-47 is the most well-ordered galaxy disc ever observed in the early Universe,” said co-author Simona Vegetti, also from the Max Planck Institute for Astrophysics.
“This result is quite unexpected and has important implications for how we think galaxies evolve.”
Was the early Universe a much more ordered place that astronomers thought? The ESO’s 39-meter Extremely Large Telescope—the world’s biggest “eye on the sky” now being built on Cerro Armazones, Chile—will look for more young disc galaxies in an effort to find out more about how galaxies evolved.
Originally published at Forbes