May 20, 2021 - Science

Ancient spiral galaxy may have formed not long after the Big Bang

An orange and yellow image of a galaxy in the early universe
The bright center of the spiral galaxy, with arms stretching out from it. Photo: ALMA/ESO/NAOJ/NRAO, T. Tsukui & S. Iguchi

A spiral galaxy similar in shape to our Milky Way may have formed just 1.4 billion years after the Big Bang, far earlier than these types of galaxies were expected to emerge, according to a new study.

Why it matters: Understanding how galaxies formed and evolved into what we see now is one of the enduring mysteries in astronomy, and this study takes astronomers one step closer toward solving it.

What they found: The new study, published in the journal Science this week, reports a spiral galaxy named BRI 1335-0417 formed less than 1.5 billion years after the Big Bang.

  • The galaxy appears to have arms stretching from a supermassive black hole and possibly a bulge of star formation at its center.
  • "These results may indicate that spiral structure have formed in a very short period of time after the disk formation, providing important circumstantial evidence to identify the formation process of these galactic structures," Takafumi Tsukui, an author of the new study, told Axios via email.
  • The authors of the study suggest the galaxy could owe its look to an interaction with a smaller galaxy (or galaxies) that may have destabilized gas in the outer part of the galaxy and triggered star formation.

The big picture: If these results are confirmed, it shows these complex, mature galaxies were coalescing before the peak in star formation in the early universe, when galaxies were thought to be building up their mass.

  • Earlier studies suggested that just after the Big Bang, the universe was populated by "protogalaxies" that were a collection of gas and dust that eventually gave rise, after billions of years, to the elliptical and spiral galaxies we see today.
  • The new study suggests that perhaps the universe started to settle down earlier than expected.

What's next: More data is needed before scientists can truly piece together the earliest days of galaxies in our universe.

  • This study shows that ALMA — the telescope used to observe the galaxy — can be used to hunt for others and compare them to ones we see relatively nearby, Tsukui said.
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