KNOW YOUR UNIVERSE
| What is a "white dwarf"? |
| When the nuclear fuel of a star ends up then the gravitational compression leaves the core composed of protons with electron flying around forming a gas- like phase - the electron gas. This electron gas can withstand the inward gravitational force and or stable, equilibrium would be achieved. Such a star is called a white dwarf. |
| What is a "black dwarf"? |
| A white dwarf gradually cools , ceases to be self luminous and ends up as a black dwarf. |
| What is chandrashekhar's limit? |
| As per S. Chandrashekhar, only those stars end up as a black dwarf whose core mass is up to 1.4 Ms ( Ms is the mass of the sun. )This is known as chandrashekhar limit. |
| What is a 'neutron star' ? |
| The star whose core mass lies in between 1.4 M4 and 5 Ms, ends up as a ' 'neutron star.' Due to excess gravitational compression, electrons are forced in to the nuclei; known as inverse beta decay. Such a neutral star is known as " neutron star " The stellar matter is of nuclear density. |
| What is 'supernova' ? |
| During the formation of a neutron star by the contraction of the central part of the star, enormous amount of gravitational energy is released. Because of this energy release the outer layers of the star explode. the star's Brightness increases sharply for sometime and then diminishes. this phenomenon is known as the " supernova ." |
| What is a ' black hole'? |
| When the core mass of a star is beyond 5 Ms, due to catastrophic gravitational contraction, the core density becomes such high that even light photons can not escape from this region. Hence this is known as 'black hole' The radius of a black - hole, rBH = 2GM/c2, where M is the core - mass. |
| What is approx diameter of our milky way? |
| Our sun is situated at a distance of two-third radius of our milky way. |
| What are thicknesses of the milky way at the centre at solar neighbour hood? |
| At the centre, it is 5000 light years, while at solar neighbourhood it is 1000 light years. |
| What is approx mass of our milky way? |
| It is about 3 ×1041 kg. = 150 billion solar masses. |
| What is hubble's law and ' BIG BANG THEORY' ? |
| U = Hr, where U = recession speed of a galaxy for us. r = distance of the galaxy from us. 1/H @ 10 - 20 billion years ( Hubble's Constant. ) BIG BANG THEORY: Initially all matter and radiation were compressed into a fiery region with extremely high temperature and immense, densities, known as the ' primordial fireball. A great explosion launched the expansion of the universe, Known as the 'BIG BANG'. |