Solar System & its origin
Its average age is about 4.8 Billion years.
Origin of Solar System
Evolutionary Theory - The material of Solar system condensed into Sun and other planets simultaneously from a single mass of gaseous cloud. Therefore, as per this theory both the Sun and other planets are of same age.
Gaseous Hypothesis (Proposed by Kent) - As per the theory, there was an existence of super-naturally created cold and hard particles which collide with each other due to gravitational attraction. The collision releases heat and gradually formed a rotating Nebula kind of structure from which the rings of matter were thrown off. This cools down to form different planets.
Nebula Hypothesis (proposed by Laplace) - It assumes a pre-existing Nebula in a rotating state. With gradual cooling, the Nebula shrank which led to more spinning and formation of a flat disc and condense to form planets.
Catastrophic/Binary theory
- Planetesimal theory (proposed by Chamberlin and Moultin) - As per the theory, the proto-star is accompanied by a companion star as the companion star came near the proto-star, its gravitational pull led to the ejection of matter from the proto-star which gradually evolved into planets. The material existed before the ejection (i.e., evolution of planets) are called Planetesimal.
- Tidal theory (proposed by Jeffry) - It proposed a very big intruding star which came near to the Sun. The gravitational pull led to the ejection of tides of materials which forms the planets.
Layers of Sun's interior and Atmosphere -
- Core - The innermost layer with highest temperature upto 15 Million degree centigrade. Nuclear Fusion reaction happens here.
- Radiative Zone - Energy from the core is carried outward by radiation through this zone.
- Convective Zone - It is a zone of convection currents where the photons through convection reaches the surface.
- Photosphere - It is the lowest layer of Sun's atmosphere. It is the brightest layer. Visible light originates from this layer. (Temperature - 5500 degree centigrade)
- Chromosphere - It is the intermediate zone which appears as a red ring during an eclipse.
- Corona - It is the uppermost layer of the Sun's atmosphere and is visible only during the total Solar eclipse. It is hotter than Photosphere. (Temperature may reaches upto 2 Million degree centigrade)
Note - Usually we see only photosphere but during a total Solar eclipse, we can see chromosphere and corona.
Solar flare - The sudden burst of storm of hot atoms released into the space is called Solar flare.
Sun spot - These are the dark portions on the photosphere with reduced temperature but strong magnetic activity.
The number of Sun spots on the surface increases or decreases over a regular period of 11 years which is called as Solar cycle or Sun spot cycle.
Solar Maxima & Solar Minima - Solar maxima is the time when high number of Sun spots are visible. (2014) And Solar minima is the time when least number of Sun spots are visible. (2019-20)
Possible impacts of Solar minima -
- The decreased magnetic activity might increase the Solar storm into the space and it might affect Astronauts in the space.
- It might also affect the communication links on the surface of the Earth with minor disturbances.
Planets - These are the celestial bodies, which revolves around the Sun.
Types of Planets -
1. Terrestrial Planets -
- Earth like planets
- Rocky & hard
- Smaller in size as compared to Jovian Planets
- Experience strong solar winds
- Thin atmosphere (because strong solar winds washes away the atmosphere leading the atmosphere of terrestrial planets to be thin)
- Closer to the Sun
- Less number of satellites
- Warmer
- Slow rotational speed
2. Jovian Planets -
- Jupiter like planets
- Gaseous planets
- Very huge
- Experience weak solar winds
- Thick atmosphere (because they are far away from the sun and experience weak solar winds)
- Far away from the Sun
- More number of satellites
- Colder
- Very fast rotational speed
There are 8 planets in our Solar System.
1. Mercury
- Smallest planet
- No atmosphere at all
2. Venus
- Also known as 'Earth's twin'.
- Hottest planet in the Solar System (because of the presence of more than 95% of Carbon di-oxide in atmosphere)
- Brightest object in the sky after the Sun
3. Earth
- Known as 'Blue Planet'
- Densest of all planets
4. Mars
- Bit smaller than the Earth
- Known as 'Red planet'
5. Jupiter
- Largest planet (approximately 11 times the size of the Earth)
- A huge spinning storm is present on the surface of the Jupiter known as 'Red spot'
6. Saturn
- Presence of visible ring around it
- Lightest of all planets
7. Uranus
- Tilted nearly at an angle of 90 degrees (rotates horizontally)
- It looks like rolling and moving around the Sun
Neptune
- Not visible to naked eyes
- A bit smaller than the Uranus
All the planets revolve around the Sun in the same direction, i.e., from West to East.
All the planets rotate from West to East on its axis except Venus and Uranus which rotate from East to West.
Astronomical Unit - It is the distance between the Earth and the Sun.
Goldilocks Zone - Zone upto which there is a possibility of life.
PYQs
The term Goldilocks zone often seen in the news in the contex of -
a) the limit of habitable zone above the surface of the Earth
b) regions inside the Earth where shale gas is available
c) search for the Earth like planet in outer space
d) search for meteorites containing precious metals
Ans - c
Satellites - These are the celestial bodies which revolves around the planets.
- Mercury and Venus - no Satellite
- Earth - 1 Satellite (Moon)
- Mars - 2 Satellites (Phobos & Deimos)
- Jupiter - 79 Satellites (Lo, Europa, Callisto and Ganymeda - Four satellites of Jupiter discovered by Galileo in 1619 and hence they are referred as Galilean Moons)
- Saturn - 82 Satellites (Saturn has maximum number of satellites)
- Uranus - 27 Satellites (Satellites of Uranus are named after the characters from the works of Shakespeare and Alexander Pope. For example - Miranda, Oberon, etc)
- Neptune - 14 Satellites
Smallest Satellite - Deimos (Mars)
Largest Satellite - Ganymeda (Jupiter)
Largest Satellite of Saturn - Titan (2nd largest in Solar System)
Note - Neptune's Satellite Triton revolves around the Neptune in an opposite direction of its rotation. It indicates that there is a possibility that Triton has not evolved from the same gaseous cloud as that of Neptune
Dwarf Planet - International Astronomic Union (IAU) in 2006 has set 3 criteria for a heavenly body to be classified as planet.
- It should have an independent orbit around the Sun.
- Enough mass to achieve hydrostatic equilibrium, i.e., spherical shape.
- It should have cleared neighbours, i.e., no major bodies of its comparable size.
Moon - It is the only Satellite of the planet Earth.
Phases of the Moon
Orbital Plane of Earth-Sun and Moon-Earth
Note - We always see the same side of the Moon because the time taken by Moon to spin on its axis is almost equal to the time taken by Moon to revolve around the Earth.
Kuiper belt or Oort Cloud - The remnants of the planets with frozen gases, rocks and debris present in the outer edge of the Solar System are known as Kuiper belt.
Asteroid - They are the small rocky and metallic objects orbiting the Sun in a belt between Mars and Jupiter.
Meteoroid - When an asteroid comes out of his belt and starts to move towards different planets, it is called meteoroid.
Meteors - It is a flash of light due to the burning of meteoroids in the atmosphere.
Meteorite - The remnant of meteoroid that reaches the Earth's surface surviving its passage to the atmosphere.
Bolite - When meteoroid explodes in the air, it is known as bolite.
Comet - These are frozen bodies of gas and dust particles held together by rocky and metallic core. they have very elongated orbit around the Sun. The tail of comet increases its length as it cones near to the sun and is always pointed away from the sun because of solar winds. Comets originate from Kuiper belt.
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Notes on other subjects
Optional Notes
Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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