Universe

 Q Draw the diagram of Ursa Major and Orion?


Q Give two points of difference between galaxy and constellations?

  • Galaxy
    • Galaxy is a vast collection of billions of stars.
    • There are so many galaxies in this universe.
  • Constellations
    • Constellation is a collection of few number of stars in a definite pattern.
    • Only 88 constellations are known so far.
Q Define 1 light year? How many meters make 1 light year? And how many light-years make one parsec?
  • The distance traveled by the light in one year is called as one light year.
  • One light year equals 9.46 into 10 to the power of 15 meters.
  • 1 parsec equals 3.26 light years.
Q Explain the following steps in the lifecycle of a star? Formation of a protostar? Formation of a star from protostar? Formation of a giant star from a star?
  • Formation of a protostar.
    • The formation of a protostar begins from a huge gaseous cloud mainly of hydrogen and some helium, and at a very low temperature of -1, 73°C. 
    • Due to gravitational force the cloud starts contracting.
    • Contraction results in the formation of small ball shaped cloud, called protostar.
    • Protostar emits no light.
  • Formation of star from protostar
    • Contraction in the protostar continues.
    • The hydrogen atoms collide with one another more frequently.
    • Temperature rises from -1,73°C to 10 to the power 7°C.
    • Nuclear fusion reactions of hydrogen start taking place.
    • Energy liberated due to the nuclear fusion. Reactions make the protostar, and it becomes a star.
    • The star is now in equilibrium under two forces acting on it.
      • Gravitational force trying to compress the gases.
      • The internal force due to nuclear energy, which stops the gaseous matter from collapsing.
  • Formation of red giant star from star.
    • The hydrogen present in the core of the star gets converted into helium.
    • The nuclear fusion reactions stop.
    • The pressure in the core decreases and the core shrinks under its own gravity.
    • Nuclear fusion reactions continue to take place in the outer shell.
    • The pressure in the outer shell increases, and therefore its size increases.
    • The autoThe pressure in the outer shell increases, and therefore it’s size increases.
    • The outer shell expands considerably while the core shrinks.
    • The star becomes Big and its color changes to red. It is called as red giant star.
Q Draw the diagram of constellation?

Q Draw the inner structure of earth?

Q Name the star which is nearest to the earth excluding the sun?
  • Alpha Centuri
Q What is a galaxy? How many galaxies are estimated to be in the universe? What is the average no stars in each galaxy?
  • Galaxy is a vast collection of billions of stars.
  • There are 10 to power 11 galaxies in the universe and 10 to power 11 stars in each galaxy.
Q Name the physical quantity whose one of the units is light year?
  • Distance
Q Name two galaxies?
  • Milky Way galaxy
  • Andromeda galaxy
Q Two constellations are seen in the sky having seven prominent stars. Which one of the two appears in the winter season?
  • Orion.
Q In which season of the year are the constellations, Scorpio and Orion visible?
  • Scorpio – summer
  • Orion – winter
Q Which of the following are constellations?
  • Pleiades
  • Scorpio.
  • Great bear.
Q What is the number of prominent stars in the Orion?
  • Seven
Q Complete the following?
  • Orion is a constellation
  • Sun is a star
  • Milky Way is a galaxy.
  • Earth is a planet.
  • Moon is a satellite.
Q The distance between a pair of galaxies , A and B is X light-years and that between another pair of galaxies C and D is 2X light-years. In which pair the two galaxies be receding from each other with greater speed? State the law and name the scientist who purposed it?

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