Milky Way’s distant lookalike discovered
The ordered galaxy challenges current ideas about how galaxies grow
spotted a galaxy which bears a striking resemblance to the Milky Way, but which is so far away we’re seeing it as it was when the Universe was just 1.4 billion years old. This is the furthest away such a lookalike galaxy has ever been found.
The galaxy, named SPT0418-47, possesses a similar rotating disc and central bulge to our own Milky Way, though it lacks its spiral arms. The discovery of this structure so early on in the galaxy’s growth came as a surprise to astronomers, as most theories predict young galaxies should be too turbulent to create such features.
“This result represents a breakthrough in the field of galaxy formation, showing that the structures we observe in nearby spiral
Astronomers have
galaxies and in our Milky Way were already in place 12 billion years ago,” says Francesca Rizzo from the Max Planck Institute for Astrophysics in Germany, who led the study.
The find will allow astronomers to study a galaxy during these critical early years of its growth. Normally galaxies from this era are so distant and dim it’s impossible to see any detail. However, this particular galaxy’s light had been greatly magnified due to gravitational lensing, where a nearer galaxy’s gravity bends the light of a more distant object. This process boosts its brightness significantly but distorts the image in the process.
Astronomers can undo this distortion, however, using computer modelling to reconstruct what the distant galaxy actually looks like. When Rizzo’s team did so, they revealed a remarkably structured and ordered young galaxy.
“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,” says Simona Vegetti, also from the Max Planck Institute for Astrophysics, who took part in the research. “This result is quite unexpected and has important implications for how we think galaxies evolve.”
The evolution of this specific galaxy, however, already looks set. Despite its resemblance to our own spiral galaxy in its youth, this distant look-alike will probably grow to become a giant elliptical galaxy. www.mpa-garching.mpg.de