Discover the oldest disk galaxy

Astronomers observe a disk galaxy 12.5 billion light-years from Earth in the early universe.

In the 13.8 billion-year-old universe, most galaxies are formed gradually over billions of years and reach their present size relatively late. For example, our Milky Way Galaxy, which has undergone a series of mergers in the first 6 billion years since the Big Bang.

Graphic simulating galaxy Galaxy DLA0817g or Wolfe Disk. (Photo: S. Dangnello).

However, a new discovery made at the world's largest radio observatory Atacama Large Millimeter / Submillimeter Array (ALMA) in Chile has "bent" the traditional models of galaxy formation. In a report published today in Nature , astronomers said they had found a giant disk galaxy, called the Galaxy DLA0817g or Wolfe Disk , formed in the early universe.

"With the help of ALMA, we now have clear evidence that the Galaxy DLA0817g existed about 1.5 billion years after the Big Bang," lead researcher Marcel Neeleman from the Max Astronomical Institute. Planck in Heidelberg, Germany said. This is the oldest and most distant disk-shaped galaxy ever known.

Galaxy DLA0817g is about 12.5 billion light-years from Earth and 72 billion times heavier than our Sun. Observations from ALMA show it is spinning at speeds of up to 272 km per second, similar to the Milky Way.

Snapshot of the Wolfe Disk galaxy from the trio of ALMA, Hubble and VLA telescopes. (Photo: Phys).

"Most of the ancient galaxies we found in the universe formed after violent mergers between small galaxies and hot air masses. It was literally a mess. This model does not create cold, orderly rotating discs like what we see in Galaxy DLA0817g, " explains Neeleman of the unusual origin of the new galaxy.

Based on computer simulations, the team suggests that a huge network of dark matter in the early universe could facilitate the formation of cold galaxies.

"We think that the Wolfe Disk grows mainly through a steady accumulation of cold gas thanks to the dark matter network. But the question is how could such a large mass of gas be established while maintaining a relatively stable turntable, " Neeleman adds.

Neeleman and his colleagues stumbled upon the Galaxy DLA0817g when they examined the light from a quasar or quasar (extremely distant and bright celestial body, with characteristic red shift). Light from the quasar is absorbed as it passes through a giant "pool" of hydrogen gas surrounding the galaxy. That's an indirect way for astronomers to know about the existence of a faint galaxy.

"This observation shows how our understanding of the universe is enhanced with the advanced sensitivity that the ALMA radio telescope brings , " said Joe Pesce, director of the astronomy program at the Science Foundation. National University of America, the sponsor for the ALMA project. "The device allows us to make new discoveries and most observations are unexpected."