Channeling Andromeda

Super computers, driven by math and intense code, give rise to simulations that intuitively show how nature works at the largest of scales.

Royal Astronomical Society - The formation of a single massive galaxy through time, from early cosmic epochs until the present day, in the TNG50 cosmic simulation. The main panel shows the density of the cosmic gas (high in white, low in black). Insets show large-scale dark matter and then gas (lower left), and small-scale stellar and gaseous distributions (lower right).

This TNG50 galaxy will be similar in mass and shape to Andromeda (M31) by the time the movie reaches the current epoch. Its progenitor experiences rapid star formation in a turbulent gas reservoir which settles into an ordered disc after a couple of billion years of cosmic evolution. A rather quiet late time assembly history without major mergers allows the galaxy to relax into an equilibrium balance of gas outflows from supernova explosions and gas accretion from its surroundings.

The real deal.

The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at a trillion solar masses (1012M☉). The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study which cited a lower estimate on the mass of the Andromeda Galaxy,[12] combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way.[13][14] The Andromeda Galaxy has a diameter of about 220,000 light-years, making it the largest member of the Local Group at least in terms of extension, if not mass.

The number of stars contained in the Andromeda Galaxy is estimated at one trillion (1×1012), or roughly twice the number estimated for the Milky Way.[15]

The Milky Way and Andromeda galaxies are expected to collide in around 4.5 billion years, merging to form a giant elliptical galaxy[16] or a large lenticular galaxy.[17] With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects[18] making it visible to the naked eye from Earth on moonless nights,[19] even when viewed from areas with moderate light pollution.

Awesome to a fault.