9

Let's take a look! While I can't quite track down the source of this image, I've found it throughout the web, so hopefully it's roughly accurate. I'm pulling it from the Wikipedia article on the Orion Arm. In this image you can also see the Orion Nebula sitting (relatively) cozily to the Sun. The distance between the two is believed to be around 1350 ...


8

A galaxy group is a set of galaxies that are close together and gravitationally bound, i.e. barring outside influences they will stay together indefinitely. That means a galaxy that is in the space occupied by the group but "passing through" it at a high velocity would not be considered part of the group. The upper limit for calling it a group is roughly 50,...


7

Assuming that Neil deGrasse Tyson is referring to the cosmic event horizon, he's right. But that doesn't really mean that galaxies "fall out of sight". He's right that they will disappear, but not because they leave the horizon. Nearby galaxies don't disappear First of all, there's a small thing to note that I'm sure he just left out to simplify matter a ...


6

I don't want to make any assumptions here regarding the Milky Way's presence in the Laniakea Supercluster simply because of how recent the discovery is. The findings could very well be accurate, but I don't want to base this answer off of them. Fortunately, I've found a few papers that get us around that little issue, as well as the University of Hawaii's ...


5

The milky way is not part of a galaxy cluster. The local group is on a lobe of the Virgo supercluster. Not all galaxies are members of large clusters, ours is in a small group. However the only difference between "group" and "cluster" is the size.


5

The Local Group contains 54 plus galaxies. Don't know that that counts as much of a cluster. Next up in scale, the Milky way is part of the Laniakea Supercluster That contains about 100,000 galaxies, so it's a bit on the large size to call a simple cluster. The well known Virgo Cluster contains about 1300 galaxies. So it's clearly a thing of intermediate ...


5

At last 80 nearby galaxies are believed to be part of a small cluster called the Local Group. The three largest members of the Local Group, have their own system of satellite galaxies. Over 50 galaxies are satellite galaxies of the Milky Way Galaxy and are closer to it than the Andromeda Galaxy is. https://en.wikipedia.org/wiki/List_of_nearest_galaxies The ...


3

The volume isn't well-defined, because the radius isn't. There are practical values for the radius such as scale length/height, half-light radius, $R_{200}$, etc. that are commonly used, depending on what you're interested in. But the densities never reach zero, so any value for the radius will be arbitrary. Moreover, you always only observe a 2D projection ...


2

In short, not much gravitational pull at all, not relative to the distance and relative velocity. Everything in the observable universe is gravitationally attracted to everything else, at least within the appropriate horizon. There should be some objects far enough apart, taking into account cosmic inflation, that gravity can't travel that far over the age ...


1

The method used to see the movement of galaxys relative movement to each other they measure the redshift of the galaxys http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/redshf.html I looked in to you question and found some answers for you in another topic on this site.Seems like the super cluster Laniekea is mowing towards the Great Attractor and ...


1

The Orion Arm is somewhat loosely defined (and many astronomers do not regard it as a proper spiral arm of the galaxy, merely a spur or some other minor feature). But at the very least this neighbourhood is hundreds of light-years across. The Zeta Reticuli system is about 39.9 light-year away. So it is in the arm.


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