Which of the following planetary, solar-planet or planet-moon pairs does not show spin-orbit resonant coupling

Question

Choices are (only one):

Io in orbit around Jupiter

Mercury in orbit about the sun

The moon in orbit about Earth

Co-orbiting Pluto and Charon

Neptune and Uranus in orbit about the sun


thanx in advance...

Answer 1

Neptune and Uranus.

I'm not so sure we have enough information (direct observation) for Pluto and Charon to make the claim of resonant coupling. But, the physics of resonantly coupled bodies says they should be coupled.

.

Answer 2

Resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers.

- Io is in a resonance orbit with Jupiter's moons Ganymede and Europa.
- If you consider the moon's rotation and orbit around Earth, there is a correlation (but not strictly a resonance).
- Pluto and Charon are not resonant, but Pluto is in resonance with Neptune (3 Pluto orbits to 2 of Neptune's).
- Neptune and Uranus resonance is sometimes shown as 2:1, but after one cycle the orbits no longer match (by about 14 degrees).

Mercury does not show a resonance (nothing close enough to Mercury so no significant orbital resonances).

Answer 3

Io orbits Jupiter,
MErcury orbits the sun
Moon orbits the earth,
Pluto and Charon orbit around eachother,
....
Neptune and uranus?
that is the one

Answer 4

Neptune and Uranus are independent planets in orbit around the same star.

Answer 5

Neptune and Uranus in orbit about the sun,
they are in separate orbits around another body (the Sun).