Hobbies And Interests
Moons
A moon is a celestial object that orbits a planet. Moons come in a wide variety of sizes and compositions. Moons can be formed when a planet's gravitational field captures an object, when one object separates from another, and when smaller objects combine into a larger body. You can usually see Earth's moon in the night sky. Earth is not the only planet with a moon. Saturn has 53 moons including some icy moons. Saturn's moons range in size from about two to 3,200 miles in diameter.
Comets
Comets orbit larger bodies like our sun and are composed of frozen gases, dust and rocks. Comets are formed at the cool, outer regions of a nebula. When a comet gets close to the sun, part of it melts. A comet's tail is created when charged particles, solar wind, from the sun push the outer layer of gases and dust away from the front of the comet.
Asteroids
An asteroid is basically a rock in space. Asteroids have no atmosphere and are too small to be classified as planets. Asteroids are formed in the inner region of a nebula where it is too hot for liquids and gases to freeze. Unlike liquids and gases, the metals and dust remain as a solid, and gravity pulls them together to form an asteroid.
Nebulae
A nebula is a large cloud of dust and gas in space. The gravitational forces between particles of dust and gas within a nebula cause them to come together. This leads to the formation of stars, planets, asteroids and comets within the nebula. Some nebulae were created at the same time the universe was created, but a dying star can also create a nebula. The Cloud Nebula was formed after a supernova.
Stars
Stars are formed when gravity causes dust and gases to group together. As it grows larger it continually gains more material. This causes it to become more dense and hot. Eventually the heat and pressure will cause the hydrogen gas to form helium in a process known as nuclear fusion. The energy given off from this process is what fuels a star and allows us to see it. A star's mass and age will determine what class of star it is.
Galaxies
Galaxies consist of stars, dust, gases, planets and other objects. Galaxies are classified as either spiral, elliptical or irregular based on their shapes. Spiral galaxies look like a round disk. As a galaxy ages, scientists theorize, it grows into an elliptical galaxy. An elliptical galaxy contains more stars than a spiral galaxy but less dust and other material. An irregular galaxy can be similar to an elliptical or spiral galaxy in composition, but the gravitational forces from another nearby galaxy gives each galaxy an irregular shape.
Black Holes
A black hole is a very massive and dense object. Stellar black holes are formed when a massive star collapses. A black hole with the same mass as the Earth would have a radius of only 0.9 cm. The force of gravity is so strong within a black hole that not even light can escape. Scientists know black holes exist because they can see objects orbiting black holes.
Man-made Objects
Objects mankind sends into space can end up as space debris. Examples include the glove that floated away during the Gemini 4 spacewalk, a camera lost during the Gemini 10 mission, old spacecraft and paint flakes. Most of this space debris falls back to Earth and burns up in the atmosphere. NASA estimates there are over 500,000 pieces of space debris.