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| 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 (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 |
updated © [2007] kidcyber