Stars and black holes

Stars and Black Hole

We all get enchanted by watching twinkling stars in the sky and also get very curious to know more and more about them; here in this article whole life history of star is explained. At present there are about approximately 1022 stars are in the entire universe out of which one can see clearly approximately 5000 stars by naked eyes in a clear sky but can only count 1000 stars at a time from any place on the globe, we had also named some of stars like Sirius (Vyadha 8.8 light years), Alpha Centuari (nearest star to us i.e. 4.29 light years), Canopas (Agastya), Spica (Chitra), Arcturus (Swati), Polaris (Dhruv) etc.

Stars appears to move from east to west (except pole star) because earth rotates from west to east on its axis. Stars are luminous objects (emits their own light) having enormous amount of energy as a result of Nuclear Fusion reactions (combining of small nuclei to form big Nucleus) taking place between Hydrogen and Helium gases present in stars. Nuclear energy is the source of huge energy in stars emitting in the form of light and heat energy. The star emits light and heat energy along with various kind of minute elementary particles of matter such as neutrino, photon, meson, positron etc together forms cosmic radiation

Happy birthday of a star starts with accumulation of particles of dust , hydrogen and helium gas at about -175oC present in the interstellar space due to their own gravitational force acting between them to form a cloud, thus formed cloud keep of contracting and dense under the effect of its gravitation pull so formed contracted mass of dense cloud is first existence of any star called PROTOSTAR . Finally, protostar starts radiating energy as heat energy produced due to friction between particles while contraction of such cloud, which in turn helps cloud to contract further resulting in increase in temperature of proto-star up to the magnitude of 107 kelvin. At such a high temperature Nuclear Fusion of hydrogen atoms into helium atoms starts in the core of star with the release of tremendous amount of heat, lights and cosmic energy. This phenomenon continues for millions of years as similar as happening in sun. Our sun had taken birth nearly about 4.6 x 109 years ago and will continue to give energy up to further 1011 years. Sun takes 250 million years to revolve around centre of milkyway galaxy.

Nuclear reaction in stars (Sun):

4 Hydrogen Nucleus = 1 Helium Nucleus + 2 Positron + Energy

Data Analysis of Solar Energy from SUN reveals that sun gives us energy 4 x 1026 joules/second on account of losing its mass at the rate of 4 x 109 kg/second and since estimated mass of sun is about 2 x 1030 kg, therefore, its estimated remaining life is about 1011 years, later it will also convert into black hole, like other stars.

Death of star onsets with the exhaustion of hydrogen gas required as a fuel for nuclear fusion reaction. With the complete conversion of hydrogen into helium the core of star starts contracting again due to gravitational pull between helium atoms and due friction between particles temperature rise which finally results in thermal expansion of outer surface of stars that also produce cooling effect in them. This phenomenon lasts till core of the star becomes too hot and outer surface too cool to together give appearance of red star. At this stage star is called Red Giant star due to its huge size (approximately 50 times bigger than sun).This Red Giant star undergoes a very amazing and fascinating colourful violent explosion called Supernova which finally results in throwing outer surface of star into interstellar space leaving behind a extremely hot highly dense core of star. Supernova explosions are very rarely observed in space as till now we observe it only 5 times, i.e., in 1006 AD, 1054 AD, 1572 (by astronomer Tycho Brahe), 1604 (Johanees Kepler) and Feb 24, 1987 (Ian Shelton).

After supernova the core of star comes to an end to form Black-Hole in following three ways depending upon the original mass of the star.

If core of the star having original mass up to 1.4 solar masses tends to contract further due to gravitational force of luminous gaseous core containing protons and electrons and appears as a white dwarf star (1000 times increase in gravitational force) which keep emitting radiation due to which temperature keep decreasing to alter gradually its yellow appearance into red and finally to black. At this stage no more heat and light radiation takes place and core becomes invisible for forever as a Black-Dwarf.

If core of star having original mass of 1.4 to 5 solar masses after supernova contracts further (due to extra recoiling force produced by supernova explosion) till density becomes about 1017 kg/m3, at which proton and electron present in core combine together to form neutrons. Such compressed core of neutrons called Neutron Stars (10 million times increase in gravitational force). Neutron Star has very high magnetic field and also emits electro-magnetic waves called PULSAR. Neutron Star also finally leads to Black-Hole .

If core of stars having original mass greater than 5 solar masses tends to get compressed highly due to very high recoiling force to attain very high density (near to infinity) which finally results to form excessively dense mass having infinite gravitation force to end as a Black-Hole.
Black-Hole are invisible as they do not emit any radiation and having so much of gravitational pull than even light cannot pass through it. Still there is no technology to find exact location of black-hole directly. Black-hole keeps on engulfing surrounding matter for trillions of years and finally comes to an end with emission of various kinds of elementary particles of matter. The existence of Black-Hole was first brought into notice by German astronomer Karl Schwarzschild in 1907. Our astronomers are still researching more about invisible object in universe and black-holes are still challenging mankind to come and pierce me if you can as at present nothing could pass through Black-Hole.

M.K. Bajpai (M.Sc.-FST)
Cell Phone: (0) 9839281700
E-mail : guddu_bajpai@rediffmail.com

Stars and black holes

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