Major moon on a geosynchronous orbit of a planet (20 hours)

So, here are the characteristics of the planet:

• 1.16 times earth mass.
• rotational period of 20 hours.
• it orbits a star of 1.1 solar masses at 1.02 AU.

I want to know if it is possible to have a moon (like earth's moon) on this orbit (geosynchronous), and also if the planet could sustain life or how would the moon affect the planet's magnetic field and tides.

Thanks!

• 1) we take 1 question per post 2) you haven't given the rotation period of the planet 3) have you done any research on your own? Wikipedia has a dedicated page to this precis topic
– L.Dutch
Commented Mar 3, 2022 at 20:49
• The geosynchronous orbit also depends on the speed of rotation; as an example, if Earth's rotational period ("day") was something other than the 24 hours that it is, the altitude of the geosync orbit would be something other than the 22,300 miles that it is. Commented Mar 3, 2022 at 20:52
• This reads like a physics homework problem I did in college. Commented Mar 3, 2022 at 21:27
• This feels very much like a homework maths question. A moon in geostationary orbit is certainly possible. The actual calculations(if you need that sort of pendantic detail) for your story world are up to you! Most readers/players would just agree to go along with your storyline of a geostationary moon. They don't need the maths. Commented Mar 3, 2022 at 21:31

I want to know if it is possible to have a moon (like earth's moon) on this orbit (geosynchronous)

Yes. This is, in fact, the equilibrium state. Earth's Moon will eventually (in another few billion years) be in a geosynchronous orbit, due to Earth's rotation slowing as the Moon's orbit recedes.

and also if the planet could sustain life

As long as other properties are favorable. Nothing here is a dealbreaker.

or how would the moon affect the planet's magnetic field and tides.

There will be no lunar tides; or rather, the lunar tides will be completely static, so all the inhabitants will notice is the solar tides. There should be no effect on the planet's magnetic field.

• Remarkable answer, for me it's counter-intuitive. I didn't downvote, but I wonder.. do you mean equilibrium (stable) orbit of only 20 hours ? would Earth's heavy moon come so close and cause no tides ? We could find our moon in a 24 hours orbit, e.g. some 300.000 years after its formation. But while it sits at that point, the moon will have to go outward. And while doing that, the month would lengthen, rather than shorten. Some sources/links would be nice, I'd upvote it. Commented Mar 3, 2022 at 22:57
• @Goodies When our Moon had a 24-hour orbit, the Earth spun a lot faster. That's why the Moon continues to move outwards. Just fiddle with the initial angular momentum in the system at formation, and there's no reason why migration couldn't stop with a mutual tidal lock at a period of 20 hours. There will be significant tidal distortion, but if the tidal bulge never moves, you won't get cyclic ocean tides. Commented Mar 4, 2022 at 0:03