The Universe is everything we can touch, feel, sense, measure or detect. It includes living things, planets, stars, galaxies, dust clouds, light, and even time. ... The Universe contains billions of galaxies, each containing millions or even trillio...
The stars that dot the night sky are only a few of the billions of stars in the universe. Stars are born inside dense clouds of gas and dust called nebulae, and form groups that are known as galaxies. Balls of ice, rock, or had known as planets move around, or orbit, many stars. Planet Earth orbits a star called the Sun and is the only place in the universe known to support life.
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Interstellar clouds Space is not as it seems. Gas and particles of dust Grains float in interstellar space (the regions between stars). In some places, the gas and dust form dense clouds called nebulae.
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The Horsehead nebula appears as a dark shape because it blocks light from the stars behind it.
What is a galaxy? Every star is part of a group called a galaxy. Galaxies range in size from dwarf ones made up of around 10 million stars to giant galaxies, which can have more than 1 trillion stars. Galaxies can have different shapes-
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the Southern Pinwheel Galaxy, for example, looks like a spiral with long, curved arms.
Planets and moons A planet is a body large enough to be shaped into a ball by it's own gravity. Planets orbit stars. Smaller bodies called moons orbit some planets. Eight planets orbit the sun,
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Including Mars, the red planet. It is the fourth planet from the Sun and has two small moons, Phobos and Deimos.
What is a star?
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Stars may look like specks of light in the night sky, but they are actually huge balls of hot gas-mainly hydrogen and helium. The Sun is a star but looks much larger than the other stars because it is a lot closer to Earth.
Other bodies The group of bodies orbiting the Sun Includes many small chunks of rock and ice, such as dwarf planets, asteroids, and comets.
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Most circle the Sun in regions called belts, including the Asteroid Belt between Mars and Jupiter, and the Kuiper Belt beyond the outer most planet.
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