Competitive Exams: Solar-System

  • Sun: 4 billion years old. Expected to glow with light and energy to 4 billion year more, and thereafter, it is expected to become white dwarf. 90% of the substance of the sun is hydrogen, 8% helium and 2% other elements. Nearest star to sun is Proxima Centauri (4, 2 light years away). Brightest star seen is Sirius or Dog-star (8.6 light years away). Visible part of sun is known as photosphere. Temperature of photosphere is 6000° C. Core-temperature of Sun is over million of degree centigrade; sun's, lower atmosphere is called chromosphere (red). Sun's upper part of at-mosphere is called chroma, it is visible only during total solar eclipse.
  • Sun-spots: Sun throws hot material towards photosphere and these results in sun-spots. These are transient dart marking on the visible surface of the sun caused by a relatively cooler area and are seen between 5° and 35° North or South of the equator of the Sun. Temperature of sun-spot is 20000 lower than the surrounding photosphere. Sun-spot indicates volatility of sun. Sun-spots maxima and minima occur periodically. Time interval between two successive sun-spots maxima or minima is
  • Solar-Flares: Powerful eruptions or radiations around the sun or associated with the sun-spot. This occur in the chromosphere of the sun. Solar-flares emits intense short-wave radiation. That intersects with the ionosphere of the earth. This may result in temporary period and appearance of brilliant display of Aurora, at the higher latitudes of earth closer to Arctic Circle and Antarctic Circles. Aurora is seen in the ionosphere of the earth. Aurora, is seen more frequently during sun-spot maximum period.
  • Solar-Prominence: It uses gaseous eruption of the sun that reach the corona of the sun and they are associated with the sun-spot. They can be seen only during total solar eclipse because of brightness of sun.
  • Solar-wind: Ionised gas found in the form of persistent stream of charged particles blowing out of corona and sweeping over the whole solar system. It is made up of plasma, i.e.. ionised gas, mostly hydrogen and helium containing an equal number of protons and electrons. Solar wind blows at steady speed of400 km/sec.
  • Pioneer-10: It was the first man-made object to leave the solar system, followed by Voyager-1 and 2 which detected the presence of solar wind at the Helio-pause, which is at the edge of the solar system.
  • Quasars: It stands for Quasi, stellar radio-sources. They are non-steller body resembling star, emitting intense radiation. It is believed to be at the edge of universe, considered as the farthest luminous object from earth.
  • Red-shift: To observer on earth ultraviolet light from receding galaxies appear as visible light emitted by galaxy will be detected in the infra-red part of the spectrum. The change of colour is/called red-shift, a manifestation of the Doppler Effect.
  • Pulsar (Pulsating star): It is neutron-star (star with mass 1.4 to 5 solar mass, in dyeing stage), rotating on its axis at very high regularity emitting intense radiation at regular intervals. They are distinguished from other type of celestial radio sources, as their emission instead of being constant over time scale of years consists of peiodic sequences of brief pulses.
  • Meteor: It is smaller pieces of matters travelling at high speed in space.
  • Meteorid: If the meteor enters in earth's atmosphere, it is called meteorid.
  • Meteorite: If the meteorid can survive atmospheric friction and falls on the ground, it is called meteorite.
  • Meteor Shower: When earth's atmosphere encounters the remains/debris of comet or larger asteroids, the number of meteor that are observed each hour increases giving the appearance of rain of stars. The annual meteor shower reaches its peak on 12 August every year.
  • Leonid Shower: It was a meteor shower witnessed from the earth in November, 1998, most prominently in the far-eastern region of the earth. This shower was due to disintegrated part of Temple-Shuttle, that entered into earth atmosphere.