Why galaxies have spiral shape?

[eosphorus]

how can this be explained?

 

[Danger]

Space Tiger answered this very nicely when someone asked about the solar system being on a 'plane'. As matter with angular momentum comes together, a disk shape is the most natural organization. The spiral aspect is probably (as my guess) the result of matter arriving at irregular intervals and attaching itself to the nearest gravity source. As more stuff accumulates, the gravitational attraction in that area increases and attracts more matter, and thus it escalates.

 

[sir-pinski]

The spiral shape of galaxies is a result of the combined effects of gravity and rotation. As a galaxy forms, gas and dust collapse under their own gravity, forming a dense central region known as the galactic bulge. As this gas and dust continue to collapse, it begins to spin, creating a rotating disk around the bulge.

The rotation of the disk causes the gas and dust to flatten out into a thin, pancake-like structure. This rotation also creates a centrifugal force that counteracts the inward pull of gravity, preventing the disk from collapsing onto the bulge.

At the same time, the gravity of the bulge and the disk causes the gas and dust to clump together, forming dense regions or "arms" that extend from the bulge. These arms are where most of the star formation in a galaxy takes place, as the gas and dust in these regions are compressed and heated, leading to the formation of new stars.

The spiral shape of a galaxy is also influenced by the gravitational interactions with other galaxies. As galaxies pass by each other, their gravitational pull can distort their shapes, creating the distinctive spiral arms we see in many galaxies.

In summary, the spiral shape of galaxies can be explained by a combination of gravity, rotation, and interactions with other galaxies. These factors work together to create the beautiful and intricate structures that we observe in the universe.