Possible rotation of a tidal locked object?

In summary, the conversation discusses the possibility of an object locked in orbit rotating on an axis if the axis is horizontal. It is determined that this is not possible due to tidal forces and the constant change in the direction of the star being orbited. The example of Earth's rotation is used to explain this concept.
  • #1
Gajillian
1
0
Hello everyone!
Real quick question here,
I've been trying to figure this out on my own all day to no avail.
Sorry if it is a dumb question...

"Can an object locked in orbit, rotate on an axis if the axis is horizontal?"

If for example a planet's north pole was locked in orbit to a sun, could it rotate on it's side? (see picture)

Thanks for your time!
GJ
 

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  • #2
Yes, tidal forces wouldn't effect rotation in that plane because any point on the planet stays the same distance from the sun and so there is no torque for the tidal force to act on.

(unless there is some second order precession effect I have forgotten about - whihcis why I normally don't risk answering questions on gyroscopes!)
 
  • #3
Welcome to PF!

Gajillian said:
Can an object locked in orbit, rotate on an axis if the axis is horizontal?

Hello Gajillian! Welcome to PF! :smile:

I think the more problematic question is: can an object rotate on an axis if the axis is towards whatever it's orbiting?

A planet's rotation must remain the same …

the Earth's points towards the Pole Star (more or less), except that precession moves the axis extremely slowly in a circle once every 25,000+ years …

but the star it's orbiting is always in a different direction. :mad:

Even if we superimposed a "horizontal" rotation on a basic "vertical" rotation, the "horizontal" addition would have to be constant.

Your object couldn't have a "horizontal" axis of rotation. :smile:
 

What is a tidal locked object?

A tidal locked object is an astronomical body, such as a planet or moon, that has a rotation period that is equal to its orbital period. This means that one side of the object always faces its parent body, while the other side is always facing away.

What causes a tidal locked object to have a rotation period equal to its orbital period?

This phenomenon is caused by the gravitational forces between the two bodies. As the object rotates, the gravitational forces from its parent body distort its shape, creating bulges on opposite sides. These bulges then cause additional gravitational forces that slow down the rotation of the object until it becomes tidally locked.

Can a tidal locked object have any rotation at all?

Yes, a tidal locked object can still have a small amount of rotation, known as a "tidal bulge." This is due to the slightly elliptical shape of the object's orbit, causing the gravitational forces to vary slightly and allowing for a small amount of rotation.

Are all tidal locked objects in our solar system in synchronous rotation?

No, not all tidal locked objects in our solar system are in synchronous rotation. For example, Mercury is in a 3:2 spin-orbit resonance, meaning that it rotates three times for every two orbits around the Sun. This is due to the influence of other planets and the Sun's gravitational forces on Mercury's orbit.

Can a tidal locked object become unlocked?

Yes, it is possible for a tidal locked object to become unlocked through various mechanisms such as tidal heating, impacts, and changes in the object's orbit. However, this process can take millions or even billions of years, and it is not a common occurrence in our solar system.

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