A gigantic rotating disk galaxy in the early Universe challenges our understanding of the cosmos and formation of galaxies.
Astronomers peeked into the early Universe with the ALMA (Atacama Large Millimeter / submillimeter Array) telescope. They were left stunned after discovering a gigantic rotating galaxy disk that existed when the Universe was only ten percent of its current age.
The rotating disk challenges traditional models of galaxy formation, leaving experts stumped.
Dubbed the Wolfe Disk after astronomer Arthur M. Wolfe, the DLA0817g galaxy is the most distant rotating disk galaxy ever observed. ALMA’s technology—together with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the NASA/ESA Hubble Space Telescope—made it possible for astronomers to see this galaxy rotating at 272 kilometers per second, similar to our Milky Way. As revealed by Scientific American, the discovery reveals the earliest of its type ever identified.
DLA0817g was first discovered by ALMA in 2017. Neeleman and his team discovered the galaxy when they studied the light from a more distant quasar. The light from the quasar was absorbed as it passed through a huge reservoir of hydrogen gas surrounding the galaxy and was thus revealed to the surprise of experts.
“Its properties are astonishingly similar to our galaxy, despite being only 1.5 billion years old,” said co-author J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz.
“While previous studies hinted at the existence of these early rotating gas-rich disk galaxies, thanks to ALMA we now have unambiguous evidence that they occur as early as 1.5 billion years after the Big Bang,” revealed lead author Marcel Neeleman of the Max Planck Institute for Astronomy in Heidelberg, Germany.
The ‘Wolfe Disk’ challenges many galaxy creation simulations, which essentially tell us that massive galaxies at this point in the evolution of the cosmos grew through many smaller galaxy mergers and hot gas accumulations. But that’s the beauty of the cosmos and the journey involved in exploring it; the more we search, the more we find what an unpredictable place it really is.
“Most of the galaxies that we found at the beginning of the universe look like the remains of a train because they underwent a consistent and often ‘violent’ fusion,” explains Neeleman in a statement.
In most galaxy formation scenarios, galaxies only begin to show a well-formed disk around 6 billion years after the Big Bang. The fact that astronomers found a disk galaxy when the Universe was only ten percent of its current age—only 1.5 billion years old—indicates that other growth factors must have dominated.
Although the discovery of Wolfe Disk is challenging and surprising, experts theorize that it may have formed—mainly—through a constant accumulation of colder gas. But even if this were the case, one of the questions that remains is how such a large mass of gas was assembled and structured while maintaining a relatively stable rotating disk.
The beauties of the cosmos resumed in one ancient galaxy that proves we are far from unraveling the mysteries of the early Universe.