• A star’s color indicates the temperature of its surface. Blue color denotes maximum temperature. Then comes yellow, then red, etc.
• The life of a star is spread over billions of years. It begins to form by compression of galactic gas and dust. Compression generates heat which in turn causes hydrogen to be converted into helium in nuclear fusion, thereby emitting large amount of heat and light.
• If die star is bigger than the sun but not more than twice as big, it will turn into a Neutron Star or
Pulsar.
• Their central density is 1014 grams per cubic cm. They are formed due to Novae or Super novae
explosion.
• Stars having mass greater than three times that of the sun, because of their great gravitational power,
have contracteso much that they have developed super density of 1016 grams per cubic cm. It is so
dense that nothing, not even light, can escape from its gravity and hence called ‘Black Hole’.
• Closest star of Solar System is Proxima Centauri (4.2 light years away). Then come Alpha Centauri (4.3 light years away) and Barnard’s Star (5.9 light years away).
(Blue > Yellow > Red )
• The life of a star is spread over billions of years. It begins to form by compression of galactic gas and dust. Compression generates heat which in turn causes hydrogen to be converted into helium in nuclear fusion, thereby emitting large amount of heat and light.
• If the star is of sun’s size, it becomes a White Dwarf. Their central density can reach up to 10 grams per cubic cm.
Pulsar.
• Their central density is 1014 grams per cubic cm. They are formed due to Novae or Super novae
explosion.
• Stars having mass greater than three times that of the sun, because of their great gravitational power,
have contracteso much that they have developed super density of 1016 grams per cubic cm. It is so
dense that nothing, not even light, can escape from its gravity and hence called ‘Black Hole’.
• Brightest star outside our Solar System is Sirius, also called Dog Star.
• Closest star of Solar System is Proxima Centauri (4.2 light years away). Then come Alpha Centauri (4.3 light years away) and Barnard’s Star (5.9 light years away).
Measurement Units of Space are :
• Light Year : It is the distance covered by light in one year in vacuum at a speed of 3 105 km/s.
• Astronomical Unit (A.U) : It is the mean distance between the earth and the sun. One light year is equal to 60,000 A.U.
• Parsec: It represents the distance at which the mean radius of earth’s orbit subtends an angle of one second of an arc. It is equal to 3.26 light years.
• Stars are self – luminous bodies that account for 98 per cent of the material in the galaxy. The rest 2 per cent consists of interstellar or galactic gas and dust in an attenuated form.
• Light Year : It is the distance covered by light in one year in vacuum at a speed of 3 105 km/s.
• Astronomical Unit (A.U) : It is the mean distance between the earth and the sun. One light year is equal to 60,000 A.U.
• Parsec: It represents the distance at which the mean radius of earth’s orbit subtends an angle of one second of an arc. It is equal to 3.26 light years.
• Stars are self – luminous bodies that account for 98 per cent of the material in the galaxy. The rest 2 per cent consists of interstellar or galactic gas and dust in an attenuated form.
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