Natural Satellites (Moons)
A satellite is any object that orbits a planet.
- Natural Satellites: Celestial bodies orbiting planets (e.g., the Moon).
- Artificial Satellites: Man-made machines sent into space (e.g., for communication).
The Earth’s Moon
- Distance: Approx 3,84,000 km.
- Revolution Period: ~27 days.
- Surface: Dusty and barren with many craters (bowl-like depressions formed by space rocks hitting the surface).
- Atmosphere: No air or water, so no life exists there.
Tip
Exploration: India has sent successful missions to the Moon, including Chandrayaan-3, which landed near the Moon’s South Pole in 2023.
Asteroids
Asteroids are small, rocky objects that orbit the Sun. They are too small to be called planets.
- Asteroid Belt: Most asteroids are found in a belt between the orbits of Mars and Jupiter.
Comets
Comets are lumps of ice, dust, and rock.
- Structure: When a comet comes close to the Sun, the heat causes the ice to vaporize, creating a glowing head and a long tail that points away from the Sun.
- Orbits: They have very long, elliptical orbits.
- Example: Halley’s Comet, which is visible from Earth approximately every 76 years.
Dwarf Planets
Some objects orbit the Sun but are not large enough to clear their path of other debris. These are called Dwarf Planets.
- Pluto: Once considered the 9th planet, it was reclassified as a dwarf planet by the IAU in 2006.