Planet Earth and Beyond Glossary
Alpha Centauri: our second closest easily visible star after the Sun; it is actually two stars orbiting very close together
amplifier: a device which amplifies (to make something bigger) the radio wave signals
antenna: the dish or other device used to collect radio waves in a radio telescope
asteroid belt: the area where most asteroids are found in our solar system, lying between the orbits of Mars and Jupiter
asteroid: a small rocky object orbiting the Sun
astronomical unit (AU): the average distance between the Earth and the Sun, equal to around 150 million kilometres
celestial: positioned in or relating to the sky, or outer space as observed in astronomy
chromatic aberration: an optical effect where different colours are refracted by different amounts in a lens leading to a distorted image
comet: a small object made of ice and dust which sometimes enters the inner solar system; when a comet enters the inner solar system, part of it evaporates to form a long tail of ice and dust pointing away from the Sun
constellation: a group of stars that form a pattern in the sky when viewed from Earth
convection: one of the three ways to transport heat energy (the other two are conduction and radiation); as a liquid or gas is heated, it becomes less dense and rises; while denser colder material sinks, creating a flow of moving liquid or gas which transports heat energy along with it
dwarf planet: a large, roughly spherical object orbiting a star which cannot be classed as a planet because it is not large enough to sweep out other objects from its orbit
filament: a threadlike structure in space containing galaxies and galaxy groups and clusters
galaxy bulge: a spheroidal (rugby ball shaped) distribution of old stars at the centre of a galaxy
galaxy cluster: a collection of over 50 or more galaxies, held together by gravity
galaxy disk: the flat distribution of stars, gas and dust in a galaxy
galaxy group: a collection of about 50 or less galaxies, held together by gravity
galaxy: a collection of millions or billions of stars, gas and dust all held together by gravity
gas giant: a large planet made mostly of gas with no solid surface; the four outermost planets in the solar system are gas giants
habitable zone: the region surrounding a star in which water can remain in its liquid state
Kuiper Belt object: a small icy object orbiting the Sun out beyond the orbit of Neptune
Kuiper Belt: region of space filled with trillions of small objects that lie in the outer reaches of the solar system, past the orbit of Neptune
light hour: the distance that light travels in one hour
light minute: the distance that light travels in one minute
light year: the distance that light travels in one year
nuclear fusion: the process by which stars produce their energy; light atomic nuclei come together and merge to form heavier atomic nuclei, releasing energy as they do so; in the Sun, hydrogen nuclei fuse with other hydrogen nuclei to form heavier helium nuclei
Oort Cloud: a hypothetical huge cloud of icy objects (comets) surrounding the Sun at the very edge of our solar system at a distance between 5,000 and 100,000 times the Earth's distance from the Sun
photosynthesis: the process by which green plants and some other organisms use sunlight to synthesise foods from carbon dioxide and water producing oxygen as a byproduct
primary mirror: the light-collecting mirror in an optical telescope
Proxima Centauri: our second closest star after the Sun
receiver: a device that detects radio wave signals
SALT: the Southern African Large Telescope, the largest optical telescope in the southern hemisphere
SKA: the Square Kilometer Array, the largest planned radio telescope array in the world
solar system: the Sun, and the collection of planets and smaller objects that orbit around the Sun
solar wind: the continuous flow of charged particles from the Sun that extends out to the far reaches of the solar system
spiral arm: a region of stars, gas and dust forming a curved shape spiraling out from the centre of a spiral galaxy
star: a huge ball of burning gas which emits energy in the form of light and heat
starlore: mythical stories about the stars, planets and constellations
sunspot: a dark region or spot which appears on the surface of the Sun from time to time; sunspots are cooler than the rest of the Sun's surface
telescope: an instrument used to look at distant objects, which makes distant objects appear brighter, larger and clearer. Some telescopes collect visible light (optical telescopes) and some collect radio waves (radio telescopes)
terrestrial planet: a planet with a rocky surface like the Earth's surface; the four innermost planets in the solar system are terrestrial planets
Universe: all of existence, including all planets, stars, galaxies, the space between objects, and all matter and energy
void: a vast empty bubble in space found between filaments