What does the sun orbit around?

Is it accurate to say that the sun orbits around something? Is it an orbit or some other movement? How fast does the sun move? For that matter, how fast does the earth move around the sun?

If the sun doesn’t revolve directly around the center of the galaxy, what does it orbit? Does that thing revolve around the center of the galaxy directly or something else?

Does the galaxy itself revolve around something other than itself? How fast does it outer edge move? It the galaxy moves (other than spinning on itself), how fast does it move?

The sun, and the entire solar system, orbits the center of the galaxy. A complete orbit takes about 230 million years.

And this nasa page fills in a couple gaps in the page linked below.

As for the Milky Way, it’s part of a “local group” of galaxies that orbit a gravitationally central point, which in our case is somewhere between the two most massive members of the group, the Milky Way and the Andromeda Galaxy.

As others have said, the sun (and solar system) orbits around the Milky Ways center of gravity. IIRC, it take approximately 200 million years to complete an orbit, and is approximately 26000 light years from the center…which, unless my napkin calculation between flights is completely wrong, is about 500,000 miles per hour. Give or take a mountain of salt.

I think it’s something like 70,000 miles per hour.

Galactic center of mass.

Not sure what this means. The best visualization I remember from my physics classes years ago is to picture one of those guys doing a hammer throw. Basically, it’s a guy swinging a weight on the end of a rope. The guy wobbles a bit due to the weight at the end, while the weight rotates or orbits around the guy as he swings it around his body. This is the same kind of thing…exactly the same thing as the earth rotating around the sun.

-XT

First things first- if you’re going to say something is moving at a certain speed, you have to specify “relative to what”. There is no absolute standard of rest in the universe. There is nothing in the universe that you could point to and say “that thing there, it’s really not moving, and everything moving relative to it is moving.” If you want to say the sun is moving, you have to specify relative to what.

When we talk about orbits, we often pretend that the thing in the center (the sun, in the case of the solar system, or actually the center of mass of the solar system) is at rest and everything else is moving.

Yes. The sun orbits around the center of the galaxy, as other posters have noted. However, the sun also orbits around the center of mass of the solar system, which is not the same as the center of the sun. We can measure this motion for other stars, and this is a popular way to find extrasolar planets. We think the sun is orbiting this center of mass at about 12 meters per second, plus or minus, mostly due to the pull of Jupiter on the sun.

To answer “how fast does the sun move”, you have to specify something relative to which you are measuring its speed. If you want the measurement relative to the center of the galaxy, we think the sun is orbiting the center of the galaxy at about 220 kilometers per second. The earth is orbiting the sun at about 30 kilometers per second relative to the sun.

The galactic center is defined as the center of mass of the galaxy, where everything in the galaxy orbits around. The sun being in the galaxy, it orbits around the galactic center.

We’re pretty sure there is a supermassive black hole near (not necessarily at) the center of our galaxy. It also orbits around the galactic center. I haven’t been able to find any information on its orbital velocity.

Center of mass of the galaxy. But those two are probably very close to each other, on a galactic scale.

I don’t think anyone’s answered this question yet.

The profile of rotational speed for spiral galaxies like ours is relatively flat, once you get beyond a certain distance from the center. (See the first graph.) So stars at the edge of the Milky Way are moving at about the same linear speed as the Sun.

The angular speed though — in degrees per million years, or what have you — will be much lower. So the outer stars will take almost twice as long to complete one orbit.

And the flat rotation curve is one of the primary pieces of evidence for the existence of dark matter. If most of the mass were concentrated in the center of the Galaxy, or even if it were distributed about the same way as the stuff we see, the outer parts of the Galaxy would be moving much slower than the inner parts. Since they don’t, there must be a bunch of extra mass that we don’t see.

I have a bad habit of being a contrarian, so I saw this quote and I felt compelled. :slight_smile: I’m not a physicist, so feel free to point out my ignorance. Recently I was exposed to an idea I had never considered before on a science program. The presenter, was talking about the nature of space, not as a void, but as a place where matter could exist. As an example, he talked about spinning objects. When an object spins, the object experiences centripetal force acting on it. Even though relative to itself, it is not moving. In other words, relative to “space” it was rotating, no relative objects required.

<blushes modestly>Me.</blushes modestly>

That’s (maybe) true about rotation, but not about linear motion.

First: Obligatory xkcd.

This is not surprising. It is velocity that needs a reference frame to be specified. In Newtonian mechanics acceleration is the same between reference frames, and rotation is a form of acceleration.

You could measure velocity relative to the cosmic background radiation (via Doppler shift), and that strikes me as a pretty good definition of absolute linear velocity.

For any specified two-object system, the actual movement is that both orbit the combined center of mass of the two. However, within our solar system, the difference in masses is such that with the possible exception of Pluto.Charon, a good first approximation of such movement is described by the smaller/less massive orbiting the larger/more massive. Even as large as the Moon is relative to Earth, the center of mass of the Earth-Moon system remains within Earth’s core. As the combined Earth-Moon system orbits the Sun, the Earth wobbles slightly, while the Moon describes a series of rosettes somewhat resembling the edge of a doily. (Technically, the Sun orbits the center of mass of the Sun/Earth/Moon system, too, but that point is perhaps a micron from the center of the Sun taken separately, since it is so massive compared to the other two components.)

All the stars in the Galaxy orbit around their combined center of mass, which may or may not be the locus of a supermassive black hole; theories differ on this, and no direct observation is as yet possible.

Chronos will probably give a better reply here, but here goes my attempt.

I think that although you could determine a “preferred” reference frame that’s pegged to the CMB, at least in a flat enough region of space — maybe by zeroing out your Doppler shift, or by minimizing its total incident energy on you — that reference frame is still nothing special as far as the laws of physics are concerned.

The CMB is like a giant spherical billboard that happens to be viewable from almost everywhere in the universe, but your velocity with respect to it doesn’t affect how anything else behaves physically, so it doesn’t really constitute an “absolute” reference frame.

No rosettes, or even inflections. The Moon’s orbit is always concave towards the Sun.

(bolding mine)

Which would be <clears throat> ahem, me.

So, excuse me if this is a stupid follow up question, but since the sun is revolving around the center of the galaxy, does that mean that the Earth is dual rotating then, revolving around the sun and the galaxy (in a seperare orbit of course)?

Yes, the logical answer as John Mace’s and DCnDC’s answers very plainly state.