Solar System Class 8 Notes Pdf
Topics Discussed:
Planets
Inner Planets: The four planets Mercury Venus Earth Mars are called Inner Planets.
These are also called terrestrial planets which means earth like planets.
Outer Planets: Jupiter, Saturn Uranus, and Neptune are called outer planets.
These planets are also called Jovian planets which means Jupiter like planets or Gas giants.
Mercury
- It is the smallest planet of our solar system
- It is the fastest revolving planet around the. sun but rotation is slower than earth.
- not the hottest planet although closest to the sun.
- has a thin atmosphere, so trapping of heat is lesser.
- Mercury is highly dense and 2nd in list after earth.
- Mercury has no moon
Venus
- 2nd planet from the sun
- brightest planet
- has a thick and toxic atmosphere of CO2 which reflects a lot of sunlight
- hottest planet due to the presence of yellowish sulfuric acid cloud which absorbs a lot of heat
- it is called earth’s twin because of its size and density.
- takes 243 days to complete one rotation, makes day longer than year.
- it rotates in clockwise direction
- has a surface temperature of 475 degree Celsius.
- No. of Moons: No Moon
Earth
- only planet that supports life
- fifth largest planet on the earth
- No. of Moons: 1
- Rotation time: 23 hrs 56 mins
- Revolution: 365.24 days
Mars
- fourth planet from the sun
- is called reddish planet because of reddish iron oxide on its surface.
- No. of Moons: 2 (Phobos, Deimos)
- It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.
Jupiter
- it is fifth planet from the sun
- Largest planet of the solar system
- Jupiter’s atmosphere is made up mostly of hydrogen (H2) and helium (He).
- the Great Red Spot is a gigantic storm and it is about twice the size of Earth
- Jupiter doesn’t support life but some of its moons might support as they have oceans beneath their crust.
- NASA’s Juno orbiter – is currently exploring this gas giant.
- No. Of Moons- 53+26=79
Saturn
- 6th planet from the sun
- 2nd largest planet of solar system
- like Jupiter, it is also made mostly of hydrogen and helium.
- a unique planet as it has thousands of rings made up of ice and rock chunks
- No. Of Moons- 53+29=82
Uranus
- Discovered in 1781 by William Herschel
- third largest planet of the solar system
- Like Venus, Uranus also rotate clockwise
- First planet to be discovered with the help of telescope
- Uranus is called ice giant, as most of its mass is a hot dense fluid of icy materials- water, methane and ammonia.
- Uranus has 13 known rings.
- Has a atmosphere of hydrogen and helium and also methane
- Methane makes Uranus blue
- Most remarkable feature: highly tilted rotational axis
- Voyager 2 is the only spacecraft to fly by Uranus
- No. Of Moons- 27
Neptune
- It was discovered in 1846 by Urbain Le Verrier, John Couch Adams, and Johann Galle.
- spacecraft visited Neptune is Voyager 2
- Neptune has a thick, windy atmosphere.
- It has six rings but hardly visible
- No. Of Moons- 14
Read Also: Chapter 4 – Materials: Metals And Non-Metals Revision Notes
Asteroids or Planetoids
Asteroids or Planetoids are rocky, airless remnants left over from the early formation of our solar system.
- Asteroids, sometimes called minor planets
- Asteroids – planetoids – were first discovered in 1801
- The size is from few meters to hundreds of kilometers in width
- These are generally found between mars and Jupiter forming a belt called Asteroid belt.
Kuiper Belt
In the year 1951, Gerard Kuiper predicted belt of icy objects beyond Neptune.
- It was discovered by David Jewett and Jane Liu in 1992.
- It is a collection of icy objects outside the orbit of Neptune called Kuiper Belt objects.
- It ranges from 30 AU to 50 AU
- Famous KBOS are dwarf planets like Makemake, Haumea, Eris and Pluto
Meteoroids
- These are lumps or small pieces of rock and iron that orbit the sun.
- On coming closer to a planet (earth), gravitation pulls them in.
Meteors
- Meteoroids with Bright streaks of light in the sky
- meteoroids Start burning on entering earth’s surface due to friction
- Also known as Shooting Stars, but they are not stars.
Meteorites
- Meteoroids that fall on a planet (earth) or moon
Comets
- cosmic snowballs of frozen gases, rock, and dust moving around the sun in elongated orbit.
- glowing gases and tail form tail of the comet
- Halley comet appears after 76 years, last appeared in 1986
Satellite
A satellite is an object in space that orbits or circles around a bigger object. There are two kinds of satellites: natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth).
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