Defining the Sun's Year: Exploring the Concept of Orbital Period for the Sun

[bunburryist]

Since the Sun orbits the Solar Systems' Barycenter about once in every 12 Earth years, wouldn't it make sense to say the sun has a "year" - at least in a casual way? After all, although the sun has a lot more mass that the Earth, it orbits the Barycenter no less than the Earth does. We talk about the other planets' "years" (in relative terms or Earth Years), so why not the sun?
I can think of two reasons right off the bat. First, how would we define a frame of reference relative to which we can define "once around"? (Perhaps we could use the path of the Solar System in its orbit around the galaxy as a reference line?) Secondly, it would seem that, due to the very irregular orbit of the Sun around the Barycenter, the "years" would never be the same length. Might the Sun "speed up" when closer to the Barycenter and "slow down" when farther away (just as a comet speeds up as it gets closer to the Barycenter)? Even if it didn't, the closer to the Barycenter it is over a given length of time the less distance it would need to traverse for a given number of degrees orbit.
I think one good reason to talk about the Sun's "year" would be that it would make it obvious that the Sun is not the gravitational center of the Solar System, and that the Sun is no less an "orbiting body" than the smallest asteroid.
Any thoughts?

 

[.Scott]

The reason that the sun's "year" is 12 years is that Jupiter's year is 12 years. And Jupiter's mass is more than the mass of all the other planets combined.

 

[stefan r]

many clumps of mass near the surface will rotate around the baricenter every day (25 Earth days).

 

[.Scott]

many clumps of mass near the surface will rotate around the baricenter every day (25 Earth days).

Including most of the corona.

 

[bunburryist]

many clumps of mass near the surface will rotate around the baricenter every day (25 Earth days).

I don't understand. Clumps of mass near the surface of the sun? "every day (25 Earth days)"

 

[chasrob]

The sun orbits around the Milky Way galaxy once every ~237 million years. That could be called the sun's "year" in a sense.

 

[stefan r]

I don't understand. Clumps of mass near the surface of the sun? "every day (25 Earth days)"

The sun rotates every 25 days. The barycenter is often inside of the photosphere.

It was a poor choice of words. I did not intend to imply that the Sun is "clumpy".

 

[bunburryist]

I read somewhere that the equator of the sun rotates faster than the poles. Do they mean that in the sense that the equator travels faster merely because it has farther to go in each rotation (just like the Earth), or does the equator actually "go around" faster, so that a point on the equator will perform a rotation in less time than a point near one of the poles. If this second description is the case, how do determine the speed of the rotation of the sun? Is it an average? This would seem to create some interesting currents, eddies, etc. in the Sun.

 

[davenn]

The sun rotates every 25 days.

That statement needs to be defined/clarified much better as the rotation isn't the same between the poles and the equator
due to it being a ball of "gas"

 

[bunburryist]

Thanks for the helpful responses!

 

[chasrob]

The sun orbits around the Milky Way galaxy once every ~237 million years. That could be called the sun's "year" in a sense.

Also called a Galactic Year.

 

[stefan r]

That statement needs to be defined/clarified much better as the rotation isn't the same between the poles and the equator
due to it being a ball of "gas"

It is usually the gas near the equator that moves around the barycenter. Here is a nice video (skip to 1:05). In 2169 the barycenter will be close to the center of the Sun.

Neither the pole nor the equator take 12 years to rotate.