Does the Milky Way orbit anything?

[Admin]

Do galaxies, including our own Milky Way, orbit anything in the universe?

Does the Milky Way orbit anything? : Read more

 

[Unclear Engineer]

A couple of thoughts:

1. How do we know that there is no other galaxy nearby, considering how hard it is to detect anything that is directly on the other side of our galaxy from Earth's position?

2. The Cosmic Microwave Background Radiation provides a frame of reference for us, with apparent blue shift in one direction and apparent red shift in the other direction, implying that our galaxy is moving at 370 Km/sec relative to the gases that released the CMBR. That is about 0.001 the speed of light. If that isn't from orbiting something, then what is causing it? (See https://telescoper.blog/2016/10/31/a-cosmic-microwave-background-dipole-puzzle/ )

 

[Aretino]

Aren't the Milky Way and the Virgo Cluster gravitationally bound?

 

[DrRaviSharma]

Where does our knowledge of nearby galaxies start to weaken, is sky survey not complete or not yet analyzed or that there are inherent limits to shape determination, as some suggested being behind our galaxy?
Another simple Q would be what does the pole star preces around? Is it part of our milky way?
At what scales of galaxies groupings and clusters do we have to use non-Euclidean geometry?
Thanks
Ravi
(Dr. Ravi Sharma, Ph.D. USA)
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http://www.linkedin.com/in/drravisharma

 

[Unclear Engineer]

The article says
"The Local Group is being pulled toward the Virgo Cluster, which contains several hundred galaxies and lies about 65 million light-years away. But the Local Group will never make it there, Mihos said, because the expansion of the universe is pulling the Milky Way away faster than the gravitational pull of the Virgo Cluster is drawing it in."

So, that does not seem to fit the definition of "bound", because it is pulling away at a rate that "will never get there". However, it is clearly "attracted". I just view this as a matter of language, not physics.

Regarding the North Star, it is in our own galaxy, something like 430 or 450 light years away from Earth. It is close to being in the alignment with the axis of rotation of the Earth, only about 1 degree off that line. So, it does have a slight motion in the sky. But, that is only apparent motion from Earth if we assume that Earth is standing still. That apparent motion does not indicate that Polaris is orbiting something.

However, the "North Star" we see from Earth really is not a single star. It is actually a 3 star system, so there are orbits involved at a much finer scale of resolution when viewed from Earth. See https://en.wikipedia.org/wiki/Polaris .

 

[DrRaviSharma]

Great clarification on North Star! Thanks.
This 3star group must rotate or corotate around the center of milky way, however!
Ravi

 

[Unclear Engineer]

Yes, our "North Star" does rotate around our galaxy. And, our galaxy rotates around the center of mass of our neighboring galaxies. The more our astronomy capabilities progress, the larger the groups of things in larger orbits are perceived. For all we know, what we call out "universe" may be just one part of something far bigger, in even larger orbits. Perhaps everything within 13.8 billion light years (or whatever its current proper distance is estimated to be), is just a blob of stuff in an orbit trillions of light years in diameter. Etc.

Until only about 100 years ago, we did not even perceive that we are in a galaxy and things like the Andromeda galaxy are not part of our own.

BBT proponents will probably chime-in to tell us that something like our "universe" orbiting anything is impossible because (they believe) that space is expanding too fast for anything that large to have a closed orbit. Maybe they are right. But, maybe not. Maybe there are other parts of space that are contracting while our >13.8 billion light year "little" part is expanding. If it really is expanding. Remember, the BBT is a theory, and previous theories astronomy have been giving way to larger and larger universes throughout our history.