Astronomers have discovered the most distant and Milky-Way-like galaxy yet. The disc galaxy was seen as it was just 700 million years after the Big Bang.
Galaxies from that time are expected to appear small and messy, but this one is surprisingly orderly. The new finding could challenge our understanding of galactic formation and evolution.
The disc galaxy has been dubbed REBELS-25. It was found by a team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), which is a network of 66 radio telescopes in the Atacama Desert region located in northern Chile.
Our universe is 13.8 billion years old, so modern galaxies like the Milky Way have had plenty of time to develop unique shapes and features like spiral arms.
In the early universe, galaxies were thought to be more chaotic and clumpy because they didn’t have the time to organize themselves in the same manner.
Over the course of billions of years, they likely would have developed the tidier structure of modern galaxies after experiencing many collisions and mergers. The evolution of characteristics like spiral arms and disc shapes would occur at an extremely slow pace, though.
But the detection of REBELS-25, when the universe was just five percent of its current age, challenges previously accepted timeframes for galaxy development.
“Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early universe evolve into the orderly galaxies of today’s cosmos,” said Lucie Rowland, the leader of the study from Leiden University in the Netherlands.
At the time of its initial discovery, REBELS-25 was already considered to be very intriguing because it showed signs of rotation.
JSirlin – stock.adobe.com – illustrative purposes only – pictured above is the Milky Way on a starry night
However, the data was not high-resolution enough to confirm that it was the most distant, strongly rotating galaxy ever observed.
The team continued to use ALMA to perform follow-up analyses, but this time at a higher resolution, to determine the structure and movement of the early galaxy with more accuracy. It is the only telescope with the capability to investigate the far-off object.
The studies exposed gas in REBELS-25 simultaneously moving toward and away from planet Earth, which was made possible due to a phenomenon known as blueshift and redshift.
The wavelength of a light source moving toward Earth gets compressed, shifting the light toward the short-wavelength, or “blue end” of the electromagnetic spectrum. So, any light coming in our direction is “blueshifted.”
When a light source is moving away from us, the wavelength of light is stretched, shifting it toward the spectrum’s “red end.”
REBELS-25 also exhibited features similar to those of the Milky Way, such as an elongated central bar of stars and even spiral arms.
The study was published in Monthly Notices of the Royal Astronomical Society.
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