Ptolemy: Geocentric Earth-Centered Universe

Copernicus: Heliocentric Sun-Centered Universe

Our Solar System

Each planet has different characteristics which separate them from each other. Eccentricity = degree of ellipse Period of revolution – time to complete 1 orbit of the Sun Mass = compared to Earth’s mass Solar System Facts:

Inner and Outer Planets: Characterized by size and composition Inner Planets: Called TERRESTRIAL (rocky bodies) –Mercury –Venus –Earth –Mars Outer Planets: Called JOVIAN or gas giants –Jupiter –Saturn –Uranus –Neptune –Pluto (Dwarf planet)

Characteristics of Terrestrial Planets They are made up mostly of rock and metal. They are very heavy. They move slowly in space. They have no rings and few moons (if any). They have a diameter of less than 13,000 km.

Mercury Desolate, cratered; long, tall, steep cliffs Mercury has a revolution period of 88 days. Mercury has extreme temperature fluctuations Very hot and very cold: 425°C (day), – 170°C (night) Even though it is the closest planet to the sun, Scientists believe there is ICE on Mercury! The ice is protected from the sun’s heat by crater shadows. Made of metal and rock; large iron core

Venus Venus is the brightest object in the sky after the sun and moon because its atmosphere reflects sunlight so well. People often mistake it for a star. Its maximum surface temperature may reach 900  F. Venus has no moons and takes 225 days to complete an orbit. N Nearly identical in size to Earth; surface hidden by clouds Hellish conditions due to an extreme greenhouse effect Even hotter than Mercury: 470°C, day and night

Like Earth, Mars has ice caps at its poles. Mars has the largest volcano in our solar system: Olympus Mons. Olympus Mons is approximately 15 miles high. Mars appears red because of iron oxide, or rust, in its soil. Mars has two moons and takes about two years to complete an orbit. Possibility of life in its past Mars

Characteristics of Jovian Planets or Gas Giants They are made up mostly of gases (primarily hydrogen & helium). They are very light for their size. They move quickly in space. They have rings and many moons. They have a diameter of less than 48,000 km

Jupiter Jupiter is the largest and most massive planet. It’s diameter is 11 times bigger than that of the Earth’s. It takes about 12 years for Jupiter to orbit the sun. Jupiter has 16 known moons. Much farther from Sun than inner planets Mostly H/He; no solid surface 330 times more massive than Earth 50 moons (Io, Europa, Callisto, Ganymede) Discovered in 1979 and confirmed in 1990 – definitive ring systems

Saturn Saturn is composed almost entirely of hydrogen and helium. Saturn has many rings made of ice. Saturn’s rings are very wide. They extend outward to about 260,000 miles from the surface but are less than 1 mile thick. Saturn has 18 known moons, some of which orbit inside the rings! It takes Saturn about 30 years to orbit the sun.

Uranus ICE GIANT Uranus is blue in color due to methane gas in its atmosphere. Uranus has 11 dark rings surrounding it. Uranus has 27 known moons and takes 84 years to complete one orbit. Composition – hot molten icy material – hydrogen and helium 19 AU distance from the Sun. Due to its extreme axis tilt – 98 degrees – it has 20 year long seasons. First planet discovered when using a telescope.

Neptune Neptune has the fastest winds in the solar system: up to 2,000 km/hr. Neptune is also blue in color due to methane gas in its atmosphere. Neptune takes 165 years to orbit the sun and has 8 moons. Neptune is a sister ice giant to Uranus. Neptune is mostly made of a very thick, very hot combination of water (H 2 O), ammonia (NH 3 ), and methane (CH 4 ) over a possible heavier, approximately Earth-sized, solid core. Neptune's atmosphere is made up mostly of hydrogen (H 2 ), helium (He) and methane (CH 4 ). Neptune has 13 moons. Neptune's moons are named after various sea gods and nymphs in Greek mythology. Neptune has six rings. 30 AU from the Sun Length of day – 16 Earth hours Named after the Roman God of the sea 17x the size of Earth

Pluto Pluto has only one moon and takes about 249 years to orbit the sun. Part of Pluto’s orbit passes inside that of Neptune, so at times Neptune is the planet farthest from the sun. Pluto was located and named in 1930, but today Pluto is considered a dwarf planet.

Asteroid Belt Components left over from the formation of the solar system. Minor planets Range in size 330 miles – larger than 10 meters in diameter Creation of comets are due to asteroids being knocked off their orbit and revolve around the sun in a different propagation. Solid rock and partly ice objects Combined mass is less than our Moon. Located between Mars and Jupiter

Discovered in the 1940’s and research over the past 70 years reveals multiple ‘dwarf’ planets in this belt. Kuiper Belt – Our Solar System is more than just 8 planets The Kuiper Belt is a disc-shaped region beyond Neptune that extends from about 30 to 55 astronomical units This distant region is probably populated with hundreds of thousands of icy bodies larger than 100 km (62 miles) across and an estimated trillion or more comets.

As new information is received and processed, astronomers and physicists are learning more about our Solar system than ever before. The Oort cloud represents our extreme edge of the Sun gravitational pull on objects and indicates the boundary layer of our Solar System. Oort Cloud “An extended shell of icy objects that exist in the outermost reaches of the solar system” Distance from the Sun ranges between 5,000 – 100,000 AU