Astronomers have discovered the most distant rotating disk galaxy to date, called REBELS-25. The structure of this disk-shaped galaxy is similar to that of modern galaxies, and it appears "shapely". However, it is located in a period when the age of the universe is only 700 million years, which is only 5% of the age of the universe today (about 13.8 billion years). According to our current theories about galaxy formation, galaxies of this early age should appear smaller and more chaotic.
The galaxies we observe today are very different from the chaotic, blocky galaxies of the early universe. These early galaxies often merge and evolve into smoother forms at a very slow rate. The current theory is that galaxies need to evolve over billions of years for galaxies to have an ordered structure like the Milky Way, such as spinning disks and spiral arms. Thus, the orderly rotating structure of the REBELS-25 was unexpected. The data suggests that REBELS-25 may have similar features to the Milky Way, such as an oval rod-like structure in the center and possibly even a spiral arm. This finding challenges our current understanding of the rate of evolution of early galaxies.
The research team observed the rotation and structure of REBELS-25 using the Atacama Large Millimeter/Submillimeter Wave Array (ALMA), which has been accepted by the Royal Astronomical Journal of United Kingdom (Rowland et al. 2024). ALMA is one of the few telescopes with sufficient sensitivity and resolution to observe galaxies so far away. The discovery of more of these early galaxies in the future, which have evolved into tangible structures, could revolutionize our understanding of early galaxy formation and the evolution of the universe as a whole.
The REBELS-25 galaxy as observed by the Atacama Large Millimeter/Submillimeter Wave Array (ALMA). (Source: ALMA, the same below)
This image of the REBELS-25 galaxy was taken by the Atacama Large Millimeter/Submillimeter Wave Array (ALMA). The image on the left shows the distribution of cold gas in the galaxy and shows signs of possible oval rod-like structures in the center. The image on the right shows the movement of cold gas in a galaxy, with blue representing movement towards the Earth, red representing movement away from the Earth, and darker colors representing faster movement. In this image, the clear red-blue demarcation indicates that the galaxy is rotating.
(The first image is a schematic image, source: pixabay)