Re:Wolf 1069B: Earth-mass planet in the habitable zone of a ...
by irq on Monday January 09, 2023 @03:42AM
(#34308133)
> I don't think we know exactly what gives a body a magnetic field, or how it is maintained, but rotation seems to be important.
The magnetic field on Earth is caused by electrical currents flowing in the rotating molten metal of the outer part of our planet’s core. You’re right, rotation is an important factor.
Re:Wolf 1069B: Earth-mass planet in the habitable zone of a ...
by mcv on Monday January 09, 2023 @07:16AM
(#34309479)
I've long suspected that tidal forces from our moon may be a big factor in keeping the outer core liquid, and thereby keeping our magnetic field active. I have no idea if that's actually true, but if it is, both rotation and a large moon might be requirements for advanced life.
Re:Wolf 1069B: Earth-mass planet in the habitable zone of a ...
by moloch-hai on Monday January 09, 2023 @05:00PM
(#34316821)
Tidal forces from the sun are remarkably close in magnitude to those from our moon. Their chaotic interaction seems to me to interfere with any big, systematic effect on Earth's rotation.
It seems possible that during certain times in the past, the lengths of the day and month (and year?) were in close enough resonance to accelerate loss of rotation for a while, until the change drove them back out of it .
Earth got its moon via a nearly, but not quite, fatal collision. Probably most other planets did not.
Ganymede's magnetic field is news to me. I don't think we know exactly what gives a body a magnetic field, or how it is maintained, but rotation seems to be important.