KERALA PSC / ASTRONOMY / LIFE CYCLE OF STARS / NOTES

 

KERALA PSC / ASTRONOMY / LIFE CYCLE OF STARS / NOTES

KERALA PSC / ASTRONOMY / LIFE CYCLE OF STARS / NOTES

 

·       There are million of stars in the sky. However, about 6000 stars are brighter enough to be visible. Star constitute about 98% in a galaxy and rest 2% include interstellar or galactic gas and duct.

·       Proto star:

Is formed by compression of galactic gas and dust which causes Nuclear Fusion, emitting large amount of heat and light. A star is thus formed.

 

·       Red Giants:

Continued Nuclear Fusion over a period of time result in depletion of hydrogen and the helium core becomes increasingly heavy, resulting into swelling and reddening of outer regions. Such stars of gigantic dimensions are termed as Red Giants. This stage gives the first indication of ageing.

 

·       Novae and Supernovae:

These are stars whose brightness increase suddenly by ten to twenty magnitudes or more due to partial or outright explosion in the star. When brightness increases to 20 magnitudes or more, it is called a Supernovae.

 

·       White Dwarfs:

A novae or Supernovae explosion in a star like our Sun may leave behind a very dense core of that star. A star of this size cools and contracts to become a White Dwarf

 

·       Neutron Star:

A Supernovae explosion in a star bigger than the Sun may leave behind an extremely dense, residual core of that star. This is called Neutron Star.

 

·       Pulsar:

The extremely dense core left after the explosion of a bigger star in called neutron star. Because of their small size, neutron stars spin very fast and while spinning, radiate all kinds of electro magnetic radiations. When this happens, the star is known as pulsar. Jocelyn Bell discovered the first pulsar in 1967

 

·       Black Holes:

Stars having mass greater than three times that of the sun, have contracted so much because of their great gravitational power and have developed super density. It is so dense that nothing, not even light can escape from its gravity and hence called Black Hole.

 

·       Fixed stars:

These are stars which do not appear to alter their relative positions in the sky. They are also called dog stars

 

·       Binary stars:

These are groups of two stars revolving round each other under mutual gravitational attraction

 

·       Temporary stars:

These are those who suddenly flare up to a greatly increased brightness and fade away after a short time. They are also called novae.

 

·       Variable stars:

These are stars the brightness of which varies from time to time.

 

·       Dwarfs are small stars, the brightest among these are blue dwarfs and the dimmest are red dwarfs.

 

KERALA PSC / ASTRONOMY / LIFE CYCLE OF STARS / NOTES