Understanding Astronomy – 10 Definitions People Will need to recognise
Astronomy refers to “the study of objects and matter (e.g. stars, planets, comets and galaxies) outside the Earth’s environment and of their physical and chemical properties”. The word astronomy (from the Greek words astron “star” and -nomy from nomos, “law” or “culture”) literally means “law of the stars” (or “culture of the stars” depending on the translation). There are 1000’s of words or definitions that you will find once you start looking into astronomy. What are the 10 definitions as a beginner you most need to know?
1. STAR: a self-heating ball of glowing gas. The Sun is the star nearest the Earth which powers life on Earth.
2. PLANETS: a large, round object orbiting a star. Earth is the planet we live on and is the third planet from the Sun. The other 7 planets in our solar system are called: Mercury, Venus, Mars, Saturn, Jupiter, Uranus and Neptune. There used to be a ninth planet called Pluto but this is now classed as a dwarf planet.
3. MOON: a natural satellite – an object orbiting a planet. Earth has one moon, though there are hundreds in our solar system.
4. COMET: a space snowball made of dust, rock and ice that orbits the Sun. Comets have tails when they are near the sun.
5. GALAXY: a large system of stars, gas, dust and empty space that rotates but is held together by gravity. Earth and its solar system are part of a galaxy called the Milky Way.
6. ASTEROID: a minor planet, actually just a giant rock, usually one that circles the Sun. There are hundreds of thousands in our solar system and more are being discovered all the time.
7. UNIVERSE: Everything! The Earth and its Moon, the Sun, the planets of the solar system, and all the galaxies – even things we haven’t yet discovered. Experts believe it’s just under 14 billion light years old.
8. BLACK HOLE: an area with a gravitational pull so strong that it sucks in anything that comes in too close.
9. SOLAR SYSTEM: The planets, moons, dwarf planets, comets, asteroids and dust that orbit the Sun, held by its gravity.
10. GRAVITY: the attraction between everything in the Universe. Gravity makes Earth and the other planets in the solar system orbit the Sun, and the moon rotate around the Earth.
Astronomers are people who study our Universe and they use telescopes to observe the night sky. An observatory is any place used to look into space. Optical observatories have a dome, often in a high-up location, housing a telescope. The roof can be opened to look at the sky. There are also radio observatories with big dishes and space based observatories – telescopes floating in space.
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