Glossary of Astronomy

Glossary of Astronomy

artificial satellite	A mechanical object launched by a rocket from Earth, which orbits a planet or a moon
asteroid	One of thousands of small bodies that orbit the Sun, mostly between the orbits of Mars and Jupiter.
astrobiology	The study of life on other planets
astronaut	A person who travels beyond the Earth & into space.
astronomer	A scientist who studies the stars, planets and the universe
astronomical unit (AU)	The mean distance between Earth and the Sun (150 000 000 km).
astronomy	The scientific study of all objects in the universe.
astrophysics	A branch of astronomy concerned with the physical nature of heavenly bodies.
atmosphere	The 'blanket' of different gases that surrounds a planet or moon.
aurora	Atmospheric event seen in the polar regions - colourful light displays occur when solar winds meet the edge of Earth's magnetic field. Known as: Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights)
black hole	Theoretical region of space with such intense gravity that light cannot escape; caused by the collapse of a star
chromosphere	The layer of crimson gas around the Sun.
comet	A heavenly body consisting of a head and a tail. At the centre of the head is a nucleus of ice and rock. Find out more about comets here
constellation	An apparent group of stars in a definite region of the sky. There are 88 recognised & designated constellations
corona	The Sun's pearly white outer layer of gas, which extends more than a million kilometres; it is visible only during an eclipse.
cosmos	The universe
docking	The joining of one spacecraft to another in space
eclipse	The blocking of light as one heavenly body passes between the Sun & another body, casting a shadow. Solar eclipse - when the Moon passes between Sun & Earth, casting a shadow on the Earth. Lunar eclipse - when Earth passes between Sun & Moon, casting a shadow on the Moon. Eclipses can be partial or total.
equinox	On about 21 March & 23 September each year, the Sun is directly over the Equator causing equal hours of day & night.
galaxy	A vast system of stars (thousands of millions) held together by gravity.There are millions of galaxies in the universe, in three main shapes: spiral, elliptical or irregular. Our galaxy is called the Milky Way & is spiral.
evening star	A planet seen in western sky after sunset, especially Venus
halo	(1) A luminous ring seen around the Moon or Sun, caused by the refraction of light through high clouds. (2) A ring of old stars which surround the Milky Way in halo fashion
interstellar space	The regions of space beyond the solar system, among the stars
Iight-year	The distance travelled by a beam of light in 1 year; equal to 9.46 million million kilometres
meteor	A brief flash of light in the sky caused by a small body from space (a meteoroid) burning up in the Earth's atmosphere; often called a 'shooting star'. An estimated 100 million meteors occur each day
meteorite	A meteoroid that reaches Earth before burning up. Meteorites are typically lumps of stone (aerolites) or iron (siderites). One found near Grootfontein in Namibia weighed some 50 tonnes.
meteoroid	A small solid object moving through space
Milky Way	Our galaxy; it contains an estimated 200 000 million stars and is of the spiral type
moon	Any natural satellite of a planet. The Moon is Earth's only natural satellite
morning star	A planet seen in the eastern sky before sunrise, especially Venus
nebula	A hazy mass of gases and particles in space
nova	The apparent sudden brightening of a star in the night sky, thought to be caused when material drawn from a companion star ignites
orbit	The elliptical path of one celestial body around another
photosphere	The visible surface of the Sun
planetarium	A kind of projector that demonstrates the motions of heavenly bodies on a hemispherical ceiling
planet	A major celestial body that does not give out its own light; usually orbiting a star. Find out more about planets here
quasar	Short for 'quasi-stellar object'; mysterious distant objects in the universe, which are powerful sources of radio waves and light
radiation	Electromagnetic waves or particles which travel through space carrying energy. Some forms are dangerous
radio astronomy	The study of radio energy emitted by celestial bodies
radio telescope	A telescope that collects radio waves from space
red shift	A shift in the light emitted by galaxies towards the red end of the spectrum, indicating that the galaxies are moving away from each other, which suggests the universe is expanding
satellite	A natural or artificial body that orbits a planet or moon
shooting star	A common type of meteor, caused by objects as small as 1 mm in diameter
solar flare	An eruption of radiation on the Sun
solar system	The Sun and its satellites
solar wind	The constant stream of atomic particles flowing outwards from the Sun
solstice	On about 21 June & 22 December every year the Sun is at its furthest from the Equator, causing the longest or shortest day.
speed of light	Approximately 300 million metres per second; the fastest speed of any object in the universe
star	A heavenly body that generates its own heat and light. Our nearest star after the Sun is Proxima Centauri, 4.28 light-years away. Some 5000 stars are visible to the naked eye
Sun	Our star; a glowing ball of gases, mainly hydrogen and helium, 109 times wider than Earth, with an average surface temperature of 6000°C.Find out more about the sun here
sunspots	Dark patches on the Sun, 1500°C cooler than its average surface temperature. Cause is unknown
supernova	The explosive 'death' of a massive star which happens after it has consumed all its nuclear fuel.
universe	Everything that exists: matter, space & energy. Generally accepted that it's 15 billion years old, it seems to be expanding, like an inflating balloon

If you use any part of this in your own work, acknowledge this source in your bibliography like this: Thomas, R. & Sydenham, S. Glossary of Astronomy [Online] www.kidcyber.com.au (2000)