More about them:
The Sun
- The Sun is a G-type main-sequence star (G2V).
- It contains more than 99.8% of the Solar System’s total mass.
- Its immense gravity governs the motions of all planets, comets, asteroids, and other bodies.
Planets
There are eight planets, divided into two main groups:
Inner (Terrestrial) Planets
Rocky, dense, and small, found inside the asteroid belt.
- Mercury – Closest to the Sun; no atmosphere; extreme temperatures.
- Venus – Similar size to Earth but with a thick, toxic CO₂ atmosphere and surface hot enough to melt lead.
- Earth – The only known planet with life; has water, oxygen, and a protective atmosphere.
- Mars – The “Red Planet”; has polar ice caps and the tallest volcano (Olympus Mons).
Outer (Gas and Ice Giant) Planets
Massive planets with thick atmospheres and ring systems.
5. Jupiter – Largest planet; mostly hydrogen and helium; has 80+ moons and a huge storm (Great Red Spot).
6. Saturn – Famous for its beautiful ring system; dozens of moons (notably Titan).
7. Uranus – An “ice giant” tilted on its side; has faint rings and a methane atmosphere giving it a blue-green color.
8. Neptune – Deep blue, very windy, and farthest from the Sun.
Dwarf Planets
Smaller spherical bodies that orbit the Sun but haven’t “cleared their orbits” of debris.
- Recognized examples:
- Pluto (in the Kuiper Belt)
- Eris
- Haumea
- Makemake
- Ceres (in the asteroid belt)
There may be hundreds or even thousands more dwarf planets beyond Neptune.
Comets
- Made mostly of ice, dust, and rock, sometimes called “dirty snowballs.”
- When near the Sun, heat causes ice to vaporize, forming a glowing coma and tail that points away from the Sun.
- Come from:
- The Kuiper Belt (short-period comets)
- The Oort Cloud (long-period comets)
Examples: Halley’s Comet, Comet Hale–Bopp, Comet NEOWISE.
Asteroids
- Rocky or metallic bodies left over from the early solar system.
- Most orbit in the Asteroid Belt between Mars and Jupiter.
- Range in size from pebbles to nearly 1,000 km (like Ceres).
- Some groups:
- Main Belt Asteroids
- Trojans (share orbits with planets)
- Near-Earth Objects (NEOs) that sometimes cross Earth’s orbit
Meteoroids, Meteors, and Meteorites
- Meteoroid: A small rock or particle in space.
- Meteor: The streak of light when it burns up in Earth’s atmosphere (“shooting star”).
- Meteorite: A fragment that survives and lands on Earth.
Moons (Natural Satellites)
- Many planets (and some asteroids) have moons.
- Over 200 known moons orbit planets in our Solar System.
- Earth’s Moon
- Jupiter’s Ganymede (largest moon)
- Saturn’s Titan (has an atmosphere)
- Neptune’s Triton (retrograde orbit)
- Mars’s Phobos and Deimos
The Kuiper Belt and Oort Cloud
- Kuiper Belt: A vast region beyond Neptune filled with icy bodies and dwarf planets.
- Oort Cloud: A hypothesized spherical shell of icy objects extending up to 100,000 AU, source of long-period comets.
Man-made Objects
- Thousands of spacecraft, probes, and satellites also orbit the Sun.
- Examples include Voyager 1 & 2, Pioneer 10 & 11, and many defunct probes now in solar orbit.
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