A zoomed-in view of many galaxies as taken with ESO’s VISTA camera, with the galaxy identified as REBELS-25 shown blown up and with enhanced brightness. (Credit: ESO/J. Dunlop et al. Ack.: CASU, CALET; Modifications: E. Siegel)
The earliest Milky Way-like galaxy, REBELS-25, was spotted rotating about its axis. It’s only 700 million years old: 5% of our present age.
The Milky Way, like all spiral galaxies, spins about its axis.
A galaxy that was governed by normal matter alone (left) would display much lower rotational speeds in the outskirts than toward the center, similar to how planets in the Solar System move. However, observations indicate that rotational speeds are largely independent of radius (right) from the galactic center, leading to the inference that a large amount of invisible, or dark, matter must be present. These types of observations were revolutionary in helping astronomers understand the necessity for dark matter in the Universe, and also explain the shapes and behavior of matter located within a galaxy’s spiral arms. (Credit: Ingo Berg/Wikimedia Commons; Acknowledgement: E. Siegel)
Stars and gas rotate in a disk, orbiting the galactic center.
The spiral galaxy UGC 12158, with its arms, bar, and spurs, as well as its low, quiet rate of star formation and hint of a central bulge, may be the single most analogous galaxy for our Milky Way yet discovered. It is neither gravitationally interacting nor merging with any nearby neighbor galaxies, and so the star-formation occurring inside is driven primarily by the density waves occurring within the spiral arms in the galactic disk. (Credit: ESA/Hubble & NASA)
However, this state — in theory — can only be achieved after enough time has passed.
Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky Way-like are inherently smaller, bluer, and richer in gas in general than the galaxies we see today. Fewer galaxies have disks and spiral shapes as we look farther back in time. Over time, many smaller galaxies become gravitationally bound together, resulting in mergers but also in groups and clusters containing large numbers of galaxies overall. (Credit: NASA, ESA, P. van Dokkum (Yale U.), S. Patel (Leiden U.), and the 3-D-HST Team)
Early on, cold streams of gas collide and collapse, forming stars.
This snippet from a supercomputer simulation shows just over 1 million years of cosmic evolution between two converging cold streams of gas. In this short interval, just a little over 100 million years after the Big Bang, clumps of matter grow to possess individual stars containing tens of thousands of solar masses each in the densest regions, and could lead to direct collapse black holes of an estimated ~40,000 solar masses. This could provide the needed seeds for the Universe’s earliest, most massive black holes, as well as the earliest seeds for the formation of stars and the growth of galactic structures. (Credit: M.A. Latif et al., Nature, 2022)
This leads to asymmetrical shapes for the earliest proto-galaxies, as confirmed…
