Massive systems held together by gravitational attraction, consisting of stellar associations, star systems, star clusters and types of interstellar clouds, stellar remnants, gasses, cosmic dust and an important but not yet completely understood component called dark matter.

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2answers
480 views

How can a spiral galaxy exist?

A spiral arm orbiting a central mass should be dispersed quite quickly as the outer elements would move more slowly than the inner ones. The Milky Way, is about 59 Galactic Years old, which, one would ...
4
votes
1answer
121 views

Baryonic Missing Mass

A recent article from a popular astronomy website tells of discovery of missing mass (not dark matter) that has puzzled astronomers for some time. Apparently, the discovery involves enhanced electron ...
2
votes
3answers
217 views

What is the strange event in this simulation of a galactic collision?

I was watching this video on YouTube: 2 Spiral Galaxies w/Supermassive Black Holes Collide Around half way, and again almost at the end, the black holes seem to suddenly give off some sort of force ...
3
votes
1answer
189 views

Gamma Ray Bubble at the center of our galaxy seen by Fermi Telescope

How could we measure high energy photons, whithout measuring them ? I can't understand how we can "see" those Gamma Ray Bubbles if they are not reaching here In this graph from Nasa you can see ...
1
vote
1answer
346 views

How is the mass of black hole at the center of our galaxy measured?

I've been watching a video about dark mater and a lot of the mass is missing in our universe. Astronomers got to this by measuring the speed that stars orbit the center of the galaxy and when they did ...
9
votes
1answer
1k views

Why do galaxies and water going down a plug hole spin?

We all experience things spinning, whether it's water down a drain, the earth on its axis, planets round the sun, or stars in a galaxy - even electrons round an atom. But why is spin so common in ...
2
votes
5answers
975 views

Is there a black hole in the centre of the Milky Way?

Is it true that the whole galaxy is actually revolving, and powered by a black hole? Has it been proven, and if it is true, how can our solar systems actually keep up the momentum to withstand the ...
6
votes
2answers
207 views

Does the recent re-count of stars in elliptical gallaxies affect our understanding of the universal mass balance?

I've seen several popular reports of a new count of low-mass stars in elliptical galaxies (here's one). Edit: Pursuant to several correct comments I've changed the title to agree with the actual ...