- Group of celestial bodies like Sun, eight planets, satellites, asteroids, comets, etc.
- Discoverer (Heliocentric concept): Nicolaus Copernicus
- Origin: 4.5 billion years ago
4.5 Bn yrs
Origin of Solar System
- Proposed by Immanuel Kant, 1755 AD
- Modified in 1796 by Laplace
- H₂ + He → Nuclear Fusion → H + H → He → Sun → H₂ (~70% composition)
⚡ Quick Recall
Nebular Theory: Kant (1755) → Modified by Laplace (1796)
| Key Fact | Value / Details |
|---|
| Location | Centre of solar system |
| Age | ~4.6 billion years |
| Diameter | 13,92,000 km (approximately 110 times of Earth) |
| Volume | 13 lakh times of Earth |
| Mass | 3,32,000 times of Earth |
| Distance from Earth | 14.96 crore km |
| Chemical composition | Hydrogen (71%), Helium (26.5%), Other Elements (4.5%) |
| Core temperature | 15 million°C (1.5×10⁷°C) |
| Period of rotation | 25 days 9 hrs |
| Source of Energy | Nuclear Fusion |
| Layer | Key Details |
|---|
| Corona (Upper layer of the Sun) | Temperature – 6000°C |
| Core (Central part) | Site of Thermo-Nuclear Fusion |
| Photosphere | Sphere of Light • Bright part / Radiant |
- Nearest star to solar system: Proxima Centauri
- Speed of Light from Sun: 3×10⁸ m/s (3 lakh km/second) → Time to reach Earth – 8 minutes 16 seconds
- Aditya–L1 Mission: Study of the Sun (Located at Lagrange point – L1) → India's first solar mission
- Midnight Sun: Arctic region • Country of Midnight Sun – Norway
⚠ Exam Trap
Aditya-L1 is positioned at
Lagrange Point L1 (not L5) — a commonly twisted detail in MCQs.
- Total Number – 8: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- Shine with sunlight
- Revolve around the Sun
Terrestrial / Inner Planets
Mercury, Venus, Earth, Mars
- Formed from rocky (solid) substances
- Solid Surface
- Few satellites
- Absence of rings
- Comparatively smaller
Jovian / Outer / Jupiter-like Planets
Jupiter, Saturn, Uranus, Neptune
- Gaseous planets
- More satellites
- Presence of rings
- Comparatively larger
⚡ Quick Recall
Planets move West → East; only
Venus and
Uranus move East → West (retrograde rotation).
1 Mercury
- Nearest to the Sun • Very hot planet
- No satellite • Absence of water
- Smallest planet • Highest orbital speed (fastest planet)
- Highest temperature difference (600°C)
2 Venus
- Lucifer Planet • Nearest to Earth
- Brightest and hottest planet of solar system (Surface temperature – 478°C)
- Composition – Sulphuric acid gas
- Evening star or Morning star (seen in west in evening and east in morning)
- Earth's twin / Earth's sister planet (similar in density, size and diameter)
- Orbits in opposite direction from other planets → Clockwise (East to West)
- No satellite
3 Earth
- Shape – Geoid • Fifth largest planet of the solar system
- Densest planet of the solar system
- Blue Planet (due to presence of water) → Only planet where life is possible
- Only natural satellite – Moon
- Nearest star after the Sun – Proxima Centauri
4 Mars
- Red planet (due to iron oxide, red soil)
- Axis tilt and day-night duration similar to Earth
- Second smallest planet after Mercury
- Two major satellites – Phobos and Deimos
- Largest volcano – Olympus Mons
- Highest mountain of solar system – Olympus Mons / Nix Olympia (3 times of Everest)
- Mission – Mangalyaan
⚠ Exam Trap
Venus and Uranus are the only two planets with retrograde (East→West) rotation — Venus among the inner planets, Uranus among the outer.
5 Jupiter
- Largest planet of the solar system
- Yellow colour – due to SO₂
- Least rotation period (on its axis)
- Rings made of silicate around
- Third brightest object after Moon and Venus
- A massive storm – Great Red Spot present
- Atmosphere full of Hydrogen, Helium and other gases
- Satellites discovered by Galileo – 4: Ganymede (largest), Io, Europa, Callisto
6 Saturn
- Second largest planet • Gas giant and massive body (Hydrogen + Helium)
- Rings made of rocks and ice chunks → discovered by Galileo Galilei
- Maximum number of satellites (274 confirmed, as of 2023)
- Density – less than water (can float on water)
- Yellow colour (Ammonia + Methane)
- Satellites – Titan (largest, similar to size of Mercury), Mimas, Tethys, Rhea, Phoebe, Enceladus, etc.
7 Uranus
- Discoverer – William Herschel (1781 AD)
- Third largest planet (by radius) • Fourth largest planet (by mass)
- Colour – Greenish (due to methane) • Tilted planet, known as Ice giant
- Coldest planet • Atmosphere made of Hydrogen, Helium
- Clockwise rotation like Venus (East to West)
- Satellites – Titania (largest), Ariel, Miranda, etc. (28 known moons)
8 Neptune
- Farthest from the sun • Ice giant
- Colour – Blue/Green (due to methane)
- Fourth largest and third heaviest planet of the solar system
- Atmosphere made of Hydrogen and Helium
- Discoverers – Johann Galle and Urbain Le Verrier (1846 AD)
- Satellites – Triton, Nereid
⚠ Exam Trap
Saturn holds the record for the most moons (274) — not Uranus. Uranus has only 28 known moons; this swap is a frequent MCQ trap.
| Planet | Diameter (km) | Rotation Time (Around Sun) | Satellites | Colour (Reason) |
|---|
| Mercury | 4,878 | 88 days | 0 | — |
| Venus | 12,104 | 224 days | 0 | Bright (due to warming) |
| Earth | 12,756–12,714 | 365.26 days | 1 | Blue (due to water) |
| Mars | 6,796 | 687 days | 2 | Red (due to iron oxide) |
| Jupiter | 1,42,984 | 11.86 years | 97 | Yellow (due to SO₂) |
| Saturn | 1,20,536 | 29.5 years | 274 | Yellow (due to ammonia) |
| Uranus | 51,118 | 84.0 years | 28 | Green (due to methane) |
| Neptune | 49,100 | 165 years | 16 | Light blue (due to methane) |
By Distance from Sun
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
By Size and Mass
- Jupiter
- Saturn
- Uranus
- Neptune
- Earth
- Venus
- Mars
- Mercury
By Density
- Earth
- Mercury
- Venus
- Mars
- Neptune
- Jupiter
- Uranus
- Saturn
By Revolution Period
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
By Orbital Speed (Highest to Lowest)
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
⚠ Exam Trap
"By Distance," "By Revolution Period," and "By Orbital Speed" all follow the same Mercury→Neptune order, but "By Size/Mass" and "By Density" are entirely different sequences — don't assume one order applies to all.
| Key Fact | Details |
|---|
| Nature | Natural satellite, non-luminous • Fossil planet |
| Sea of Tranquility | First step of Neil Armstrong |
| Distance from Earth | 3,84,400 km |
| Radius / Diameter | Radius – 1737.5 km • Diameter – 3475 km |
| Rotation + Revolution | 27.3 days (59% part of Moon is visible) |
| Moon's Gravity | 1/6th of Earth |
| Highest Mountain | Leibnitz (10,668 meters) |
| Moonlight to Earth | 1–3 minutes |
| Scientific Study | Selenology |
| Mission | Chandrayaan I, Chandrayaan III |
Comet / Tail Star
- Bodies made of stone, dust, ice and gas
- While approaching the sun, burning of dust and ice forms a bright tail
- Tail always points away from the sun
- Halley's Comet: 1986 → 76 years later → visible again in 2061
Asteroids
- Big-big rocks
- Small bodies orbiting the sun between Mars and Jupiter
- First asteroid discovered – Ceres
- Visible with naked eye – 4 Vesta
- Asteroid named after Pt. Jasraj (2019)
Meteorites
- Remains of comets and asteroids
- Revolve around the sun
- Burn in the mesosphere of the atmosphere
- Meteor → Shooting star
- Meteorite – those which fall on Earth without burning completely
- Meteor showers / sighting month – December, January
- Lyrid Meteor shower – April
⚡ Quick Recall
Asteroid Belt lies between
Mars and Jupiter · Kuiper Belt lies
beyond Neptune.