Some astronomers think that the two gas-giants do not sport solid surfaces secreted beneath their immense and heavy gaseous atmospheres, although others suggest that the jumbo-size duo do, indeed, harbor relatively small cores of rocky-icy stuff. The two other large inhabitants of the outer limits of our Sun's family are Uranus and Neptune, which are both classified as ice-giants, because they harbor large icy cores secreted deep down beneath their heavy, dense gaseous atmospheres which, though very massive, are not nearly as heavy as the gaseous envelopes possessed by Jupiter and Saturn.
Earth's Moon is the largest and brightest object suspended in the darkness of the starry night sky. It is both lovely and enchanting, and it has, since ancient times, inspired curiosity and wonder in human beings who gaze up at the mysterious sky after the Sun has set. As such, Earth's Moon has long served as the inspiration for imaginative, wild and marvelous tales--it is the stuff of mythology and folklore. The "Man in the Moon" refers to several fantastic images of a human face that certain traditions see outlined in the gleaming disk of the full Moon. In November 2013, astronomers using data from the lunar-orbiting twins composing NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, announced that they have been acquiring new and fascinating insight into how this bewitching "face," etched on our Moon's disk, received its captivating and enchanting good looks!
A moon is defined as a natural satellite that orbits a larger body--such as a planet--that, in turn, orbits a star. The moon is kept in its position both by the gravity of the object that it circles, as well as by its own gravity. Some planets are orbited by moons; some are not. Some dwarf planets--such as Pluto--possess moons. In fact, one of Pluto's moons, named Charon, is almost half the size of Pluto itself, and some planetary scientists think that Charon is really a chunk of Pluto that was torn off in a disastrous collision with another object very long ago. In addition, some asteroids are also known to be orbited by very small moons.