A recent observation has challenged the current theory about the way galaxies formed in the early days of the universe.
Many cosmologists believe that the universe began with a Big Bang. Therefore, galaxies forming in the early universe could experience very chaotic physical processes, which made them appear disordered.
However, the new study has cast serious doubt on this picture. Scientists observed a star-forming galaxy called ALESS 073.1, which is 12.5 billion light-years away and appears very much like a typical mature galaxy.
Due to ALESS 073.1’s great distance from Earth, its light takes billions of years to reach us. This enabled the team to explore the galaxy’s formation and evolution during its infancy.
The team, led by scientists at Cardiff University, used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to analyze the kinematic properties of ALESS 073.1.
With careful analyses, the team obtained one of the sharpest direct images of this primordial galaxy. The unprecedented images allowed the team to undertake a detailed study of its internal structure.
Galaxies can have a variety of shapes, sizes, and colors. Generally, galaxies are made of several components, such as a central bulge and spiral arms.
“We discovered that a massive bulge, a regular rotating disk, and possibly spiral arms were already in place in this galaxy when the Universe was just 10% of its current age,” lead author of the study Dr. Federico Lelli, who undertook the work at Cardiff University’s School of Physics and Astronomy, said in a statement.
“In other words, this galaxy looks like a grown adult, but it should be just a little child.”
Co-author of the study Dr. Timothy Davis, from the School of Physics and Astronomy, said: “This spectacular discovery challenges our current understanding of how galaxies form because we believed these features only arose in ‘mature’ galaxies, not in young ones.”
One of the key features that Davis was referring to is the presence of a bulge. It was believed that massive bulges should form very slowly, either through the merger of smaller galaxies or by some internal processes.
However, the kinematic properties of ALESS 073.1 have revealed that massive bulges can form extremely quickly, and nearly half of its stars were shown to be in a bulge.
Some mature galaxies such as our Milky Way can have spiral arms, which give them a distinctive spiral shape.
Much to the team’s surprise, structures similar to spiral arms were spotted in ALESS 073.1. It was long believed that early galaxies are chaotic and turbulent rather than having regular, well-organized structures like spiral arms.
“A galaxy like ALESS 073.1 just defies our understanding of galaxy formation,” concluded Dr Lelli.
The new study has been published in Science.