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Summary
Geography Class 06

Last class revision(5.15 PM).

Solar system(5.23 PM):

  • Sun:
  • It is a dwarf star.
  • The age of the sun is 4.8 billion years.
  • Layers of the Sun:
  • Core:
  • The innermost layer of the Sun's interior where nuclear fusion reaction happens.
  • It has the highest temperature which is 15 million degrees C.
  • Radiative Zone:
  • The energy from the Core is transferred outward by radiation through this zone.
  • Convective Zone:
  • The energy is transferred through Convection currents to the surface. 
  • Photosphere:
  • It is the 1st layer of the Sun's atmosphere.
  • Visible light originates from this zone.
  • It is the brightest layer of the Sun.
  • Its temperature is 5500 degrees C.
  • Chromosphere:
  • It is the intermediate zone of the sun's atmosphere and emits colorful light.
  • Corona:
  • It is the uppermost layer and is visible only during a total solar eclipse.
  • It is hotter than the photosphere with a temperature of 2 million degrees Celsius.
  • Solar Flare:
  • It is the sudden burst of energy with a storm of hot atoms released into space.
  • Sunspots:
  • These are the dark spots in the Photosphere.
  • They experience reduced temperature but strong magnetic activity.
  • The Number of sunspots increases or decreases over some time.
  • Solar maxima are when the sunspots are highest and solar minima are when they are lowest.
  • The period between solar maxima or minima is 1 sunspot cycle(11 years).

Planets of our solar system(6.06 PM):

  • They are of two types, Terrestrial planets (Earth-like) and Jovian Planets (Jupiter-like).
  • Differences between the Terrestrial and Jovian Planets:
  • Terrestrial Planets Jovian Planets
    Earth-like Jupiter-like
    High density Low density
    Rocky Gaseous
    Smaller in size Large in size
    High solar winds Lower solar winds
    High temperature Low temperature
    Thin/no atmosphere Thick atmosphere
    Less no. of satellites Large no. of satellites
    No rings Rings
    Speed of rotation lower Very high speed of rotation
  • Mercury:
  • It is the smallest planet.
  • It is nearest to the sun.
  • It has no atmosphere.
  • Venus:
  •  It is called Earth's twin.
  • It is the hottest planet (very high greenhouse effect due to the presence of Co2)
  • Earth:
  • It is called a Blue planet.
  • It is the densest planet of all. 
  • Mars:
  • It is called a Red planet.
  • the possibility of life due to its presence in Goldilocks Zones(habitable regions in the universe).
  • Jupiter:
  • The largest planet in the solar system (11 times bigger than the earth).
  • The giant red spot (a spinning cyclonic storm that appeared on Jupiter 400 years ago) is the most characteristic thing about Jupiter.
  • Saturn:
  • It has the most prominent and spectacular ring system.
  • It is the lightest planet in the solar system.
  • Uranus:
  • Its axis of inclination is tilted by 98 degrees.
  • It rotates from East to West(Retrograde rotation).
  • Neptune:
  • It is the farthest planet.
  • It cannot be seen with the naked eye.

Satellites(7.06 PM):

  • It is a body that revolves or orbits around another planet (and not around the sun).
  • Mercury and Venus have no satellites.
  • Earth has one satellite - Moon.
  • Mars has two satellites-  Phobos and Deimos.
  • Jupiter has 79 satellites, four of which are important (discovered by Galileo/ Galilean satellites) Io, Europa, Ganymede(the largest satellite), and Callisto.
  • Saturn has the maximum number of satellites i.e. 82.
  • One of the important satellites is Titan, which is the second-largest satellite in the solar system.
  • Titan is one of the most probable regions in the solar system where there is the possibility of life's existence. 
  • Satellites of the Uranus are named after the characters of the play written by Shakespeare, for example, Miranda, and Oberon.
  • Triton, a satellite of Neptune, rotates in the opposite direction of Neptune.
  • Moon:
  • The period of rotation of the moon is equal to the period of revolution of the moon around the earth, which is equal to 27.3 days.
  • Therefore the other half of the moon is not visible from the earth.

Dwarf planet(7.36 PM):

  • In 2006, the International Astronomical Union set the conditions for a body to be declared a Planet:
  • It should have an independent orbit around the Sun.
  • It should have enough mass to achieve hydrostatic equilibrium i.e. spherical shape.
  • It should have a cleared neighborhood.
  • Officially there are 5 dwarf planets, there are the bodies that fulfill 1st 2 conditions but not the 3rd one, for example, Pluto, Eris, Ceres, Haumea, and Makemake.

Other important bodies in solar system(7.51 PM):

  • Asteroid belt:
  • It is a belt of Asteroids which are small rocky and metallic bodies with cores made up of Iron and Nickel.
  • They are orbiting around the Sun in a belt between Mars and Jupiter.
  • Kuiper Belt:
  • This is a belt of remnants of planets with frozen gases, rocks, and debris materials.
  • Oort cloud:
  •  It is a layer of Ice pieces of space debris surrounding the entire solar system.
  • Meteoroids:
  • When an asteroid comes out of its orbit and moves toward the earth.
  • Meteor:
  • It is a flash of light due to the burning of meteoroids in the earth's atmosphere.
  • It is also called a Shooting star.
  • Meteorite:
  • It is the remnant of a meteoroid that has survived its passage through the earth's atmosphere.

The topic for the next class: Comet, Solar, and Lunar eclipses.