Hobbies And Interests
Planets
As of 2011, eight celestial objects are classified as planets within Earth's solar system. The International Astronomical Union presents a definition of a planet as being an astronomical object which has the size to become rounded by its own gravity but not big enough to create thermonuclear fusion. Planets also orbit stars, as in the case of the planets in the solar system, which revolve around the Sun. Planets can vary in size immensely, and their nature varies. For example, Neptune and Uranus have very cold surfaces and are known as ice giants. Jupiter and Saturn are called "gas giants."
The Sun
The solar system contains a large star called the Sun. Essentially, the sun is a ball of gas made of plasma, which appears to shine in the night sky due to the thermonuclear fusion reactions of the hydrogen within. The Sun also contains elements such as helium and oxygen. The Sun has a mass of 332,830 times that of Earth.
Asteroids
An asteroid is a celestial object in orbit around the sun, which isn't big enough to be a planet but is not a comet either; they are sometimes referred to as minor planets. Asteroids vary in size, with some asteroids measuring over 120 miles in diameter, while others are less than 10 miles in diameter. A large number of asteroids are found in the solar system's asteroid belt, which is located between the planets Mars and Jupiter. Scientists have discovered and classified thousands of asteroids.
Moons
Moons are satellites in orbit around planets, and while Earth has only one of these, other planets in the solar system have many more. For example, Uranus possesses 21 while Saturn has 18. The size of a moon can vary too. Jupiter's moon, Ganymede, measures 3,280 miles in diameter, while Deimos, a moon of Mars, is a mere 10 miles in diameter. As they travel around their orbits, moons also rotate themselves, with many moons, such as Earth's moon, rotating in the same number of days as it takes for the moon to completely orbit its planet. This is called synchronous rotation. This means the moon, while it rotates slowly, always points the same face toward Earth.
Comets
Comets have a core of ice and dust, and release dust as they travel in their orbits around the sun. Observers on Earth can sometimes spot comets by their trail, which is formed by the dust which falls behind the comet due to the radiation encountered as the comet nears the sun.