Galaxies, the cosmic cities of the universe, explained by astrophysicist

[Admin]

Galaxies are glittering cities, massive metropolises full of stars, dust, gas, black holes, magnetic fields, cosmic rays, dark matter and more.

Galaxies, the cosmic cities of the universe, explained by astrophysicist : Read more

 

[rod]

"Astronomers have identified three kinds of galaxies: spirals, ellipticals and irregulars, and the differences between those kinds of galaxies reveal their complicated histories."

My observation. Spiral galaxy spiral arms are short-lived objects relative to the Hubble time age for the universe or the galaxy age, commonly about 10-11 billion years old. Most spiral arms do not live more than 80-100 million years. Example, New Theory of Evolution for Spiral Galaxy Arms, http://www.sciencedaily.com/releases/2011/04/110420111343.htm, April 2011. Another report, Why Galaxies Have Spiral Arms, https://skyandtelescope.org/astronomy-news/galaxies-spiral-arms-2908201623/, August 2016. "However, by this reasoning, the arm should quickly wrap itself around the galaxy’s center, destroying the spiral. That generally doesn't happen. Thus for at least half a century, astronomers have debated why these patterns persist."

Spiral galaxies with their arms is difficult to explain given their generally short lifetimes for the spiral arms. Density wave and perhaps other methods are used to reconcile the age differences or at least keep the spiral arms generated again, and again so we can see them today in our telescopes, otherwise spiral arms would disappear long ago and not be visible today (using the BB cosmology for the age of the universe).

 

[Atlan0001]

There is extra-Earth gravity, extra-solar systemic (extra-stellar) gravity, extra-galactic gravity, even -- to my mind's eye -- extra-universe (u) gravity. Outland horizon or rim gravity. All that [other] gravity, the gravity of the non-local (versus the local), closed up to the relatively distant outside of any and every local. The infinity of gravity. The infinities of gravity. My forest versus trees analogy, the gravity of the totaled forest [versus] the gravity of the individual trees -- each and every individual tree -- that make up the forest. And once more analogy; each and every tree is in the forest, and the forest is in each and every tree (each and every finite universe (u) is in the infinite Universe (U), and the infinite Universe (U) is in each and every finite (point infinitesimal) universe (u)).

If it weren't for such a non-local representation of gravity, the local would close up -- close in on itself, and keep on closing in on itself, to an [absolute] of nothingness.