The Solar System: The Sun & the Planets

Measuring Distances in the Solar System The astronomical unit (AU) is used to measure distances within the Solar System The average distance from the Sun to Earth is approx. 150 000 000 km 1 AU = 150 000 000 (1.5 x 108) km Planets Big & Small The Sun is the largest object in the Solar System, the next largest are the planets.

The Inner Planets = Terrestrial Planets Mercury, Venus, Earth & Mars Small, rocky planets Located between the Sun and Asteroid Belt

Mercury Location – Inner Orbital Period – 88 days Rotation – 59 days Atmosphere – None Temperature – -180 to 400 0C # of Moons – 0 Rings – 0 Unique Characteristics No atmosphere to trap heat Contains craters Rarely visible in our night sky because it is so close to the Sun

Venus Location – Inner Orbital Period – 224.7 days Rotation – 243 days (opposite direction) Atmosphere – carbon dioxide, nitrogen Temperature – 462 0C # of Moons – 0 Rings – 0 Unique Characteristics Brightest object in the sky after the Sun & Moon

Earth Location – Inner Orbital Period – 365.26 days Rotation – 24 h Atmosphere – Nitrogen, Oxygen Temperature – -88 to 58 0C # of Moons – 1 Rings – 0 Unique Characteristics Ozone – filters some of damaging radiation from the Sun Temperatures are constant 70% of planet’s surface is water

Mars Location – Inner Orbital Period – 687 days Rotation – 24.65 h Atmosphere – Carbon dioxide, Nitrogen Temperature – -90 to -5 oC # of Moons – 2 Rings – 0 Unique Characteristics Called the ‘red planet’ due to its rusty soil Very dry Once had volcanoes, glaciers & water No signs of life

The Outer Planets = Gas Giants Jupiter, Saturn, Uranus & Neptune Large, composed of gas Atmospheres consist mainly of the gases hydrogen and helium

Jupiter Location – Outer Orbital Period – 11.9 years Rotation – 9.85 h Atmosphere – Hydrogen, helium, methane Temperature – -148 oC # of Moons – 63 Rings – Yes Unique Characteristics Largest planet (11x the diameter of Earth) Features are its coloured bands, the Great Red Spot & hurricanes Orbiting rings of rocks

Saturn Location – Outer Orbital Period – 29.5 years Rotation – 10.65 h Atmosphere – Hydrogen, helium, methane Temperature – -178 oC # of Moons – 60 Rings – Yes Unique Characteristics Second largest , no solid core Cloudy & windy, over 1000 separate rings

Uranus Location – Outer Orbital Period – 84.1 years Rotation – 17.3 h (on it’s side) Atmosphere – Hydrogen, helium, methane Temperature – -216 0C # of Moons – 27 Rings – Yes Unique Characteristics Winds blow up to 500 km/h

Neptune Location – Outer Orbital Period – 164.8 years Rotation – 15.7 h Atmosphere – Hydrogen, helium, methane Temperature – -214 0C # of Moons – 13 Rings – Yes Unique Characteristics Uneven orbit, Bright blue & white clouds Has a dark region called the Great Dark Spot, which appears to be the center of a storm

Planet Rotations

To be considered a “planet” a celestial object must; 1 To be considered a “planet” a celestial object must; 1. Be in orbit around a star (such as the Sun) 2. Have enough mass to be pulled into a stable sphere shape by gravity 3. Dominate its orbit (i.e., its mass must be greater than anything else that crosses its orbit)

Dwarf Planets A celestial object that orbits the Sun and has a spherical shape but does not dominate its orbit. Ceres, Pluto, Haumea, Makemake, and Eris Pluto’s tilted orbit crosses Neptune’s orbit

Planet Locations

Smaller Members of the Solar System Asteroids are composed of rock & metal. Although they orbit the Sun, they are too small to be considered planets. Most asteroids lie in the asteroid belt, located between Mars & Jupiter.

ASTEROID BELT 700,000 to 1.7 million asteroids with a diameter of 1 km or more. Over 200 asteroids are known to be larger than 100 km.

A meteoroid is a piece of metal or rock that is smaller than an asteroid. Sometimes they get pulled in by Earth’s gravity. They burn up in the Earth’s atmosphere, creating a bright streak of light across the sky, known as a meteor (shooting star). Larger meteors do not burn up completely in the atmosphere and their remains, which we call meteorites, crash to the ground.

DID YOU KNOW? A leading theory on the extinction of dinosaurs suggests that a 10 km wide meteorite impact is what caused the extinction of these animals 65 million years ago.

Wolfe Creek Crater in Australia

Comets Comets are large chunks of ice, dust, and rock that orbit the Sun. As a comet approaches the Sun, radiation and solar wind from the Sun, causes a gaseous tail to form, pointing directly away from the Sun. A dust tail forms in the direction from which the comet originated. Most comets have 2 tails; gaseous tail dust tail

Comets

Homework WS P.317 #5, 6, 8