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Today w are going to tell you Solar System so friends read and share it if you like this post in blog share it more Solar System
The study of the universe on a grand scale is called cosmology.
Big Bang Theory : The Big Bang theory argues that billions of years ago, cosmic matter (universe) was in an extremely condensed state and in such a high temperature and pressure that they prevented the formation of atoms.
Galaxies bring out three major forms – Spiral, Elliptical and Irregular.
Spiral galaxies have a central nucleus with great spiral arms trailing round it. The Milky Way and the Andromeda Galaxy belong to this group.
Elliptical galaxies show purely elliptical shape without any spiral arms. They range in shape from spherical, elliptical into extremely saucer-shaped ones and account for seventeen percent of the known galaxies.
Irregular, as the name suggests, shows no definite geometric pattern or shape.
The Milky Way. The Milky Way is our home galaxy. A peculiar feature of this galaxy is a bright band of light that runs almost in a perfect circle through it. Milky Way belongs to a cluster of some twenty four glaxies called “the local group”.
As seen from the Earth, this band looks like river of light flowing through the sky. Actually, it is made of millions of scintillating stars, which from the distance seem to be placed in close proximity to one another. Modern westerners have called this river of light the Milky Way. The name is now applied to the galaxy as a whole.
The Milky Way is a spiral galaxy. The main body of the galaxy is a disc 100,000 light years across with a globular nucleus of about 16,000 light years in diameter and far stretching spiral arms (in one of which our solar system is located). The galaxy consists of over a hundred billion stars rotating about its centre in a stately average period of some 230 million years.
Our galactic nucleus is about 32,000 light years from the Sun. It appears to be a rotating disc of gas. In this rotating disc massive activities are going on. One such scene of activity is near the centre of the galaxy. Here, new stars are being born continually. The area is already crowded with full gorwn stars. The steallar density here is of the order of a million stars per cubic parsec (3.26 ligh years).
Stars account for ninety eight per cent of the matter in a glaxy. The rest two percent consists of interstellar or galactic gas and dust in very attenuated form. The normal gas-density between stars (Interstellar gas) throughout the galaxy, is about one-tenth of a hydrogen atom per cubic centimetre (cm3) volume.
Black Hole is an ancient star that has collapsed matter. It is so dense that it creates a powerful gravitational force that draws everything nearby, including stars, into its centre. Gravity becomes so intense in the hole that nothing escapes, even light. Hence the objects is dark and cannot be viewed directly.
1. Hydrogen and helium constitute about 98 percent of the Sun’s mass. In contrast, the terrestrial planets have large quantities of such elements as oxygen, silicon and iron.
2. All the planets revolving around the Sun in the same direction, i.e., in an elliptical orbit and they all lie near the plane of the Sun’s rotation.
3. The orbital paths of planets occur within approximately the same plane so that the solar system has the shape of flat disc.
4. The distance of the planets from the Sun can be described by simple relationship called Bode’s, Law which says that each planet tends to be roughly twice as far from the Sun as its next Sunward neighbour.
5. The planets have different composition as indicated by their differing densities, as well as by Moon, Earth and meteorite samples.
Sun and Planets
Sun Diameter : 1,384 km (865,000); Age : 4.5 b.y; Statellites : nine planets.
A rather ordinary, middle-age star, the gaseous Sun may reach a temperature 27 million degree Celsius at its core. Its eleven year cycle is now approaching a solar maximum, a period marked by requent Sunspots and flares. On Earth, some radio waves will be disturbed and the amazing sky streamers called Northern Lights will appear.
Mercurry, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto Death of a Star
When the hydrogen in a star is converted into heavier atoms like helium, the density of the star increases many fold and the star is well near dead. The Core of dying star contains the densest matter in the universe. The ultimate destiny of a star, according to present theories, is that it will turn into one of three things, according to its mass – White Dwarfs, Neutron stars or Pulsars and Black Holes.
¨ The time it takes for half of the atoms of a radioactive isotope to decay is called half-life.
¨ Some unstable atomic nuclei undergo radioactive decay.
¨ Radioactive isotopes can be used to absolutely date geologic materials.
¨ As a radioactive isotope decays, it may leave fission tracks in surrounding material.
¨ Fossils are the remains or traces of organisms that lived in the past.
¨ Fossils can be used to date sedimentary rocks.
¨ Great forests developed during the Carboniferous Period.
¨ Homo Spiens evolved about 0.125 million years ago.
1. Seismic Studies : The study of seismic waves, i.e., the vibrations, usually created by disturbances within the Earth’s outer crust, reveals some useful information about the Earth’s internal structure. There are three types of seismic waves.