Page 192 - Science Class 08

Astronomy : Scientific study of celestial bodies

Galaxy : A group of billions of stars
Universe : All the galaxies including the stars, planets and other heavenly bodies and in
empty space in between
Light Year : Distance travelled by light in one year
Constellation : A group of stars forming some recognised shapes

Solar system : The sun and its family which includes planets, moons and other celestial
bodies
Orbits : The elongated path on which the planets revolve around the sun

Asteroid : Large numbers of rocks that lie between the orbits of Mars and Jupiter
Comet : Heavenly body that revolves around the sun, but has a very long period of
revolution
Meteor : Small object in space made up mainly of stone, which enters the earth’s
atmosphere
Meteorite : Meteor which falls from space on the earth’s surface.

Crescent : The carved sickle shape
Waning moon : Decrease in apparent size after the full moon

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i Astronomy is a branch of science that deals with the study of universe and heavenly bodies.
i Astronomers are the scientists who study about the universe and heavenly bodies.
i The universe is made up of galaxies, stars and empty spaces in between.
i All the natural bodies that exist in the space are called celestial or heavenly bodies.
i A group of stars forming some kinds of patterns is known as constellation. For example,
Ursa Major, Ursa Minor, Orion, etc.

i The sun, eight planets and their moons and other heavenly bodies form the solar system.
i Eight planets in sequence (from the sun) are Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus and Neptune.
i Satellite is a body that orbits around a planet. Moon is the natural satellite of the earth.
i Comets are lumps of dust, rock and ice that remain invisible outside the solar system. As
they get closer to the sun, their ice melts, cloud and gas gather around the comet.

i Meteoroids are the particles consisting of dust and small rocks that occupy space between
the planets.

i Most of the meteoroids burn up in the atmosphere to become meteors or shooting stars.
i Artificial satellites are man-made satellites sent into the space to gather information about
universe, weather, different abnormalities in atmosphere, etc.

192 Science-8