Having such a big Hill radius is one way of explaining why Jupiter has a lot of moons and can affect the orbits of passing comets so strongly. This gives Jupiter a lot of gravitational influence on the space around it. This is because Jupiter is more massive than the Earth and has a stronger gravitational pull, but more importantly because it is further from the Sun than Earth so the Sun's gravity is weaker at Jupiter than at Earth. For comparison, Jupiter's Hill sphere has a radius of 0.36 AU, which is much much larger than the Earth's Hill sphere. If the Moon somehow ended up outside Earth's Hill sphere, the Moon would orbit the Sun instead of the Earth just like all the other planets, asteroids, and comets. Loosely speaking, the Hill sphere defines the space where the Earth's gravity is more important than the Sun's gravity on another object. The Moon orbits the Earth because the Moon is about 380,000 km from Earth, well within Earth's Hill sphere, which has a radius of 1.5 million km (0.01 AU or 235 Earth radii). Earth is a satellite of the Sun and the Moon is a sub-satellite orbiting Earth. Outside the Hill sphere, a sub-satellite would be lost from its orbit about the satellite.Īn easy example is the Sun-Earth-Moon system. The region of space around a satellite where a sub-satellite can exist is called the Hill sphere. Thanks to Patrick "I Love Asteroids" Taylor for all of his shared wisdom.
#PLANETARY ANNIHILATION SYSTEM DESIGNER MOONS CRASHING UPDATE#
Question is, do moons have satellites? But you don't get away with it that easy :-), so if not, why not? Looking forward to your response!ĭue to the popularity of this question and the large number of follow-up questions I have received, I have decided to update my answer with the help of someone much more knowledgeable on the subject than I am. However, I do not recall seeing a reference to bodies (satellites-squared?) orbiting moons. There are satellites (moons) orbiting around the planets, and asteroid pairs and more. We observe planets, asteroids, comets, etc.
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