MYSTERY OF STARS

Welcome to my presentation

Naimul ArifCSE0905004

Ancient people had no

idea about the size or the

distance of the stars

They thought that the stars were like glittering pearls attached with the inner surface of the

semispherical sky

Greek and Indian mythology are vastly related with the

stars.

People imagined the clusters of stars as different

characters

Science & research in ancient age started following the stars:

First calendar of history

Ancient astronomy

Trigonometry

Aristotle told about the stars that

they are constant for ever and no

change will happen to them.

People believed it for many

years.

He was proved false in

1572 by Tyco Brahe

The sun is also a star.

After all of the hydrogen has been used, the

small stars turns into red giants.

In case of giant stars, helium starts fusion and

produces carbon, oxygen, silicon, iron and

gradually goes towards lead.

After generating heavy molecules fusion stops and

supernova occurs.

Towards death of the star

What happens after the death of a star?

The answer was given by Indian scientist Subramanian Chandrasekhar

Chandrashekhar mathematically proved that, if the mass of the star is:

*Less than 1.44 solar mass:

Black dwarf

*More than 1.44 solar mass and less

than 3 solar mass:

Neutron star

*More than 3 solar mass:

Black hole

When the mass of the star is less

than 1.44 solar mass:

*The star cools, expands in size. Called Red Giant.

The star is completely dead now. No change will occur to it for ever.

2

4*The core collapse on itself, turns into a white dwarf

containing He .

*Then white dwarf gets cooled again and gradually becomes unable to emit light . It is now called black dwarf.

If the mass of the star is between 1.44 and 3

solar mass then it turns into a neutron star:

*The core of the star compresses into a very small volume.

*The protons and electrons in the core forms neutrons. Ultimately the whole star turns into a ball of neutrons.

*The neutron star rotates around its axis with a great angular velocity.

*This star generates electromagnetic wave continuously.

*As electromagnetic wave is found from it with a certain frequency, it is called Pulsar.

If the mass of the star is more

than 3 solar mass:

*After the explosion, the core of the star starts to compress because of gravitational force.

*After compression, it turns into a sphere with a very small radius and extremely high density.

*The gravitational pull of the star is then so high that no matter even light cannot escape from it.

*Then it is called black hole.

Thank you all for

watching my

presentation.

Good bye

NAIMUL ARIF0905004