Question
Describe the solar system. Name the eight planets in order. What are satellites, constellations, and asteroids? How do stars differ from planets?
Solution — Step by Step
Our solar system has the Sun at its centre, with eight planets orbiting it. The planets, in order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Mnemonic: My Very Educated Mother Just Served Us Noodles.
The inner four (Mercury to Mars) are rocky/terrestrial planets. The outer four (Jupiter to Neptune) are gas giants (or ice giants for Uranus and Neptune).
| Feature | Star | Planet |
|---|---|---|
| Light | Produces its own light (nuclear fusion) | Reflects light from a star |
| Size | Very large (Sun is 109x Earth’s diameter) | Smaller |
| Twinkle | Yes (due to atmospheric refraction) | No (steady light) |
| Temperature | Extremely hot (Sun’s surface: 5500°C) | Relatively cooler |
Satellites (moons) — bodies that orbit planets. Earth has 1 (Moon), Jupiter has 95+. The Moon is the closest celestial body to Earth.
Asteroids — rocky objects orbiting the Sun, mostly in the asteroid belt between Mars and Jupiter.
Comets — icy bodies that develop a glowing tail when near the Sun. Halley’s Comet appears every 76 years (last seen 1986).
Constellations — patterns of stars as seen from Earth. Examples: Ursa Major (Saptarishi), Orion (Hunter), Leo. They are not physically grouped — the stars may be at vastly different distances.
flowchart TD
A[Solar System Bodies] --> B[Star: Sun]
A --> C[Planets: 8]
A --> D[Satellites/Moons]
A --> E[Asteroids]
A --> F[Comets]
C --> C1[Inner: Mercury Venus Earth Mars]
C --> C2[Outer: Jupiter Saturn Uranus Neptune]
D --> D1[Moon orbits Earth]
E --> E1[Asteroid belt: Mars-Jupiter]
F --> F1[Halleys Comet: 76-year period]Why This Works
The solar system is organised by gravity — the Sun’s enormous mass keeps everything in orbit. Closer planets orbit faster (Mercury: 88 days), farther ones slower (Neptune: 165 years).
Common Mistake
Students still list Pluto as a planet. Pluto was reclassified as a dwarf planet in 2006 by the IAU because it has not “cleared the neighbourhood around its orbit.” The solar system has 8 planets, not 9.
Venus is the hottest planet (not Mercury) because its thick CO₂ atmosphere traps heat via the greenhouse effect. Mercury has no atmosphere, so heat escapes. This is a favourite exam trick question.