How do scientists know where the northern and/or southern poles are on other planets?

Question

In an article our teacher read to us, the author wrote about the northern hemisphere of Mars and Venus. Do all planets have a magnetic north and south? Is it magnetism that has something to do with it or is it something else?

Answer 1

All planets rotate on an axis.  The invisible "poles" are where the points basically stay stationary as the rest of the planet spins around it.  And for the most part, they are magnetic as well I believe

Answer 2

Yup, they're located on the tips of the rotational axis. They aren't magnetic though .... here on Earth they just happen to coincide with our magnetic field. Remember, magnetic poles and N/S poles are different terms. Did you know that the magnetic poles on Earth shift over time ..... over thousands of years, the could be foundin ANY orientation!

Answer 3

Good answers so far, but I would like to disagree with Douglas.  Researchers still do not know exactly what causes magnetism in the poles, so it's presumptuous to claim that it's merely chance that the magnetic and orbital poles match up pretty closely.  Most researchers think that it has to do with circulation below the surface of the earth--that circulation is affected by the rotation of the earth, and therefore the magnetic poles would tend to line up with the orbital poles.  It's not EXACTLY on the poles, but it's pretty close.  Over the past few billion years, the magnetism tends to flip directions every once in a while (recorded in the geologic record), but this always seems to be lined up, more or less, with the poles.  I think it would be a reasonable hypothesis that other planets with liquid cores could or would have magnetic fields, and that they would be lined up with the poles. The sun certainly does and it's lined up with its rotation.   The actual designation of "North" and "South" are arbitrary, just like "Left" and "Right".

Answer 4

Most heavenly bodies are spherical as matter accretion under gravitational force tends to make it spherical. Then, it acquires angular momentum and rotates. The ends of axis of rotation are called poles. Naming one as north and the other as south is due to its orienatation on par with earth's, it is arbitrary.

You can observe the rotary motion just by looking at it. If it becomes difficult you can observe doppler shift of its light spectrum.

Answer 5

poornakumar is right.  The professional international astronomical union says that "north" on other planets is the spin axis direction that lines up most with the solar system's north pole.   The Earth's north pole is tilted about 23 degrees from the solar system's north pole.

So "north" has nothing to do with magnetic north.  Some planets have very weird magnetic fields.