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 man or women who travels beyond the Earth and into space.

astronomer A scientist who studies the stars, planets and the universe

astronomical unit
(AU) The mean distance between Earth and Sun (150 000 000 km).

astronomy The scientific study of all the objects in the universe.

astrophysics A branch of astronomy concerned with the physical nature of heavenly
bodies.

atmosphere The 'blanket' of different gases which surrounds a planet or moon.

aurora An atmospheric phenomenon seen around the polar regions in form of
colourful displays of light, attributed to sunspot activity. Known as the
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 grouping of stars within a definite region of the sky. There
are 88 officially recognised and 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 and another body, casting a shadow. A solar eclipse occurs when the Moon passes between the Sun and the Earth, casting a shadow on the Earth. A lunar eclipse occurs when the Earth passes between the Sun and the Moon, casting a shadow on the Moon. Eclipses can be partial or total.

equinox The time of year when the Sun is directly over the Equator and there are equal hours of day and night. Equinoxes occurs on about 21 March and 23 September each year

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

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). A specimen 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 projection instrument 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 An telescope that collects radio waves from space

red shift The shift in the light emitted by galaxies towards the red end of the
spectrum; it indicates that the galaxies are moving away from each other, which suggests that the universe is expanding

satellite A body, natural or artificial, 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 The time of year when the Sun is furthest from the Equator, causing the longest or shortest day. Solstices occur on about 21 June and 22 December every year

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 the average surface
temperature. Their cause is unknown

supernova The explosive 'death' of a massive star which happens after it has
consumed all of its nuclear fuel.

universe Everything that exists: matter, space and energy. Most astronomers set its age at 15 billion years; the universe seems to be expanding, like an inflating balloon

Acknowledge this source in your bibliography like this:
Thomas & Sydenham, Glossary of Astronomy [Online] www.kidcyber.com.au (2007)

Back to Space

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 man or women who travels beyond the Earth and into space.
astronomer	A scientist who studies the stars, planets and the universe
astronomical unit (AU)	The mean distance between Earth and Sun (150 000 000 km).
astronomy	The scientific study of all the objects in the universe.
astrophysics	A branch of astronomy concerned with the physical nature of heavenly bodies.
atmosphere	The 'blanket' of different gases which surrounds a planet or moon.
aurora	An atmospheric phenomenon seen around the polar regions in form of colourful displays of light, attributed to sunspot activity. Known as the 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 grouping of stars within a definite region of the sky. There are 88 officially recognised and 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 and another body, casting a shadow. A solar eclipse occurs when the Moon passes between the Sun and the Earth, casting a shadow on the Earth. A lunar eclipse occurs when the Earth passes between the Sun and the Moon, casting a shadow on the Moon. Eclipses can be partial or total.
equinox	The time of year when the Sun is directly over the Equator and there are equal hours of day and night. Equinoxes occurs on about 21 March and 23 September each year
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
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). A specimen 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 projection instrument 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	An telescope that collects radio waves from space
red shift	The shift in the light emitted by galaxies towards the red end of the spectrum; it indicates that the galaxies are moving away from each other, which suggests that the universe is expanding
satellite	A body, natural or artificial, 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	The time of year when the Sun is furthest from the Equator, causing the longest or shortest day. Solstices occur on about 21 June and 22 December every year
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 the average surface temperature. Their cause is unknown
supernova	The explosive 'death' of a massive star which happens after it has consumed all of its nuclear fuel.
universe	Everything that exists: matter, space and energy. Most astronomers set its age at 15 billion years; the universe seems to be expanding, like an inflating balloon