Chapter 29 Our Solar System The earth is

Chapter 29 – Our Solar System "The earth is the cradle of humankind, but one cannot live in the cradle forever. " -- Konstantin Tsiolkovsky, 1895

29. 1 Overview of our solar system OBJECTIVES Describe early models of our solar system. Examine the modern heliocentric model of our solar system. Relate gravity to the motions of celestial bodies.

Early Ideas Geocentric , meaning “Earth Centered” In the early 1500 s, Nicholas Copernicus formulated the heliocentric model of the solar system.

Copernicus Nicolaus Copernicus found that in a heliocentric model of the solar system, • the inner planets move faster in their orbits than the outer planets, • giving the appearance from Earth that some planets move in a retrograde motion. (http: //imagine. gsfc. nasa. gov/Images/people/Copernicus. gif )

Retrograde Motion Retrograde motion is the movement of a planet in an opposing direction across the sky.

Galileo’s discovery of Jupiter’s moons proved that not all celestial bodies orbit Earth; therefore, Earth is not necessarily the center of the solar system.

Kepler’s First Law Kepler’s first law demonstrates that each planet has an elliptical orbit of unique size and shape with the Sun at one focus.

AU Earth’s average distance from the Sun: 1. 496 x 108 km or 1 astronomical unit.

Planets’ Orbits All of the planets (& former planets) and their satellites orbit the Sun in the same direction, and all their orbits, except Pluto's lie near the same plane.

Eccentricity When a planet is closest to the sun in its perihelion orbit, it is at ______ and when it is aphelion farthest from the sun, it is at _____.

Ellipses Terms to be familiar with. • Major axis • Foci • Semi-major axis • Perihelion • Sun • Aphelion

Eccentricity e= Distance between foci Major axis length

Kepler’s Second Law Closer Faster Farther slower Kepler’s second law is an imaginary line between the Sun and a planet that sweeps out equal amounts of area in equal amounts of time.

Center of Mass Isaac Newton determined that each planet does not orbit the Sun but instead orbits a center of mass between it and the Sun.

29. 1 Overview of our Solar System Quiz

29. 2 The Terrestrial Planets OBJECTIVES Describe the properties of the terrestrial planets. Compare Earth with the other terrestrial planets.

Precession The wobble of the Earth’s rotational axis is called precession. The Moon’s gravitational force on Earth causes the sideways push that is responsible for precession.

Mercury has the largest daynight temperature difference of all the planets in the solar system. Mariner 10 image of Mercury

Venus is the planet most similar to Earth in physical properties, such as diameter, mass, and density. Venus - Computer Simulated Global View Centered at 180 Degrees East Longitude

Venus (more) The high concentration of carbon dioxide (CO 2) in the atmosphere of Venus inhibits infrared radiation from escaping and keeps the surface extremely hot.

Earth is the only known planet in our solar system where H 2 O is present in three states, solid, liquid & gas. Image by Reto Stöckli (land surface, shallow water, clouds).

Terrestrial planets are close to the size of Earth and have solid and rocky surfaces, while the gas giant planets are larger, more gaseous, and lack solid surface.

29. 2 The Terrestrial Planets

Atmospheric conditions of the four terrestrial planets Mercury • almost nonexistent • mostly oxygen and sodium Mercury Venus • thick clouds • primarily of carbon dioxide and nitrogen • Include sulfuric acid Venus Earth Mars • moderately dense • composed of 78% nitrogen and 21% oxygen • thin and there is consistent wind. • composition is similar to Venus’s Earth Mars

29. 3 The Gas Giant Planets OBJECTIVES Describe the properties of the gas giant planet. Identify the unique nature of the object “formerly-known-as-the-Planet-Pluto”.

29. 3 The Gas Giant Planets

29. 3 the object “formerly-known-as-the- Planet-Pluto”.

Composition The gas giants are composed primarily of lightweight elements, such as hydrogen, helium & methane. Jupiter Saturn Uranus Neptune

Rapid Rotation The rapid rotation of the largest gas giant Jupiter, causes its clouds to flow in alternating cloud types called belts and zones. Jupiter Belts are low, warm, darkcolored clouds that sink. Zones are high, cool , light-colored clouds that rise.

Blue Color Neptune and Uranus , the two gas giants appear blue because of the methane in their atmosphere. Uranus Neptune

Neptune has clouds and atmospheric belts and zones similar to those of Saturn and Jupiter. Neptune

Pluto’s Eccentricity Pluto’s orbit is so eccentric that while at perihelion, Pluto is closer to the Sun than Neptune is. Pluto's orbit seen from the plane of the ecliptic, showing its high inclination compared to the other planets The eccentric orbit of Pluto is 50 AU from the Sun at aphelion and almost 30 AU from the Sun at perihelion.

Terrestrial and the Gas giant planets Both are categories of the planets of our solar system Terrestrial planets • four planets close to the Sun • Mercury, Venus, Earth, and Mars • solid, rocky surfaces • smaller Gas giant planets • farther from the Sun • Jupiter, Saturn, Uranus, and Neptune • more gaseous • lack a solid surface • larger

29. 2 & 29. 3 Quiz (8 pts) Riddle me this.

29. 4 Formation of Our Solar System OBJECTIVES Describe how the planets formed from a disk surrounding the young sun. Explore remnants of solar system formation.

Interstellar Cloud Interstellar cloud, a cloud of gas and dust from which stars and planets are formed.

Interstellar cloud can condense and become concentrated enough to form a star and possibly planets. The dense concentration of gas at the center of the solar nebula eventually became the Sun. Solar Nebula Theory

Planetismals are tiny grains of condensed material that accumulate and merge together to form these large bodies possibly growing until they reach hundreds of kilometers in diameter. Planetismals

Asteroids Bodies of interplanetary debris that orbit the Sun with most in the area between Mars and Jupiter are called asteroids.

Comets are small, icy body made of ice and rock that has a highly eccentric orbit around the Sun. The Oort cloud and the Kuiper belt are two cluster of comets. Comets Haley 's comet seen here in 1986. It will appear again in 2062.

Meteor The result when Earth intersects a cometary orbit is a meteor shower.

Meteor is interplanetary material that burns up and becomes a bright, glowing streak of light in Earth’s atmosphere. Two examples are the Perseids (August) & Leonid (November).

Meteorite Is interplanetary material that enter’s Earth’s atmosphere and collides with the ground rather than burning up.

29. 4 Quiz