Question
Classify the members of the solar system. How are inner planets different from outer planets? Name two constellations visible from India.
(CBSE Class 8 — Stars and the Solar System)
Solar System Classification
flowchart TD
A["Solar System Bodies"] --> B["Star: Sun"]
A --> C["Planets (8)"]
A --> D["Dwarf Planets"]
A --> E["Small Bodies"]
C --> F["Inner / Terrestrial"]
C --> G["Outer / Gas Giants"]
F --> F1["Mercury"]
F --> F2["Venus"]
F --> F3["Earth"]
F --> F4["Mars"]
G --> G1["Jupiter"]
G --> G2["Saturn"]
G --> G3["Uranus"]
G --> G4["Neptune"]
E --> E1["Asteroids"]
E --> E2["Comets"]
E --> E3["Meteoroids"]Solution — Step by Step
The solar system consists of:
- Sun — The central star, containing 99.8% of the solar system’s total mass
- 8 Planets — Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (remember: My Very Educated Mother Just Showed Us Neptune)
- Dwarf planets — Pluto (reclassified in 2006), Ceres, Eris
- Natural satellites — Moons orbiting planets (Earth has 1, Jupiter has 95+)
- Asteroids — Rocky bodies in the belt between Mars and Jupiter
- Comets — Icy bodies that develop tails when approaching the Sun
- Meteoroids — Small rocky fragments; they become meteors when they enter Earth’s atmosphere
| Feature | Inner Planets | Outer Planets |
|---|---|---|
| Also called | Terrestrial | Gas giants / Jovian |
| Surface | Rocky, solid | Gaseous, no solid surface |
| Size | Smaller | Much larger |
| Moons | Few (0-2) | Many (dozens) |
| Rings | None | Yes (Saturn most prominent) |
| Distance from Sun | Closer | Farther |
| Examples | Mercury, Venus, Earth, Mars | Jupiter, Saturn, Uranus, Neptune |
Ursa Major (Saptarishi) — The seven-star pattern visible in the northern sky. It looks like a ladle or a question mark. Two stars of Ursa Major point towards the Pole Star (Dhruv Tara).
Orion (Hunter) — Visible in winter evenings. It has three stars in a straight line forming the “belt.” The bright star Sirius lies near Orion.
Why This Works
The solar system formed from a single rotating cloud of gas and dust (the solar nebula) about 4.6 billion years ago. Inner planets are rocky because the Sun’s heat blew away lighter gases from the inner region, leaving only heavier elements. Outer planets retained their hydrogen and helium envelopes because they formed far from the Sun where temperatures were low enough for gases to condense.
Constellations are patterns formed by stars as seen from Earth. The stars in a constellation are not actually close to each other — they just appear grouped from our viewpoint.
Alternative Method — Size Comparison
A quick way to remember planet order by size (largest to smallest): Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury. The mnemonic: Just Sit Up Now, Eat Vegetables More Mornings.
CBSE loves asking why Pluto is no longer a planet. The answer: Pluto has not “cleared the neighbourhood” of its orbit — it shares the Kuiper Belt with many similar objects. A planet must (1) orbit the Sun, (2) have enough mass for a round shape, and (3) clear its orbital neighbourhood. Pluto fails the third condition.
Common Mistake
Students mix up meteors, meteoroids, and meteorites. Meteoroid = the rocky body in space. Meteor = the streak of light when it burns in the atmosphere (“shooting star”). Meteorite = the piece that survives and lands on Earth. Think of it as: meteoroid (space) → meteor (atmosphere) → meteorite (ground).