Universe had spiral galaxies 4 billion years sooner than expected: study Premium

New study challenges previous beliefs on spiral galaxy formation, revealing more in the universe's youth than expected.

A new study has revealed more spiral galaxies in the universe’s youth than astronomers had expected.

The universe is about 13.8 billion years old and is home to different kinds of galaxies, from spiral to elliptical and those with or without bulges. Astronomers previously believed spiral galaxies formed about 6 billion years ago, but a new study by a group of astronomers from the University of Missouri in the U.S. has called this belief into question. It was published on June 11 in the Astrophysical Journal Letters.

While the universe’s younger galaxies have tended to be spiral, the older ones have a variety of shapes. Astronomers study them to understand how they formed and evolved. But studying the older galaxies is more difficult because the light from them is fainter.

An important idea in astronomy is that as the universe cooled down from a dense plasma state, it contained more and more hot gas. They formed clumps of matter that eventually gravitated to become galaxies. These early galaxies had irregular shapes and lacked disks. But as they cooled as well, they formed hot, thick disks that later became thinner and finally spiral ‘arms’ — a process that took billions of years.

This theory is now suspect. “Our work shows that this cooling down and spiral formation occur around the same cosmic time,” said Vicki Kuhn, a graduate student at the University of Missouri and a member of the study.

Astronomers routinely see stars forming in real-time but since all the galaxies have already formed, they use a sort of astronomical archaeology to study them. “We don’t see proto-galaxies,” said Girish Kulkarni of the Tata Institute of Fundamental Research, Mumbai, who was not involved in the study. “What we do then is study how the galaxies evolve. The spiral galaxy fraction is one way to do this biography.”

The first step is to use light of the infrared and optical wavelengths to detect galaxies in the early universe. Since older galaxies are harder to detect, we need powerful telescopes. Ideally, astronomers would like to observe light emitted when the universe was around 500 million years old, when the galaxies were thought to be forming.