Overview of the Solar System Shaped like a thin disk Chapter 7 Astronomy Overview of the Solar System Shaped like a thin disk Held in place by the Sun’s gravitational force

Planets, to correct relative size

1 AU Astronomical Unit Average distance from Earth to Sun 149,597,870 1 AU Astronomical Unit Average distance from Earth to Sun 149,597,870.691 kilometers

Artist’s view of the Solar System Figure 7.1

Planets and their orbits Figure 7.2

Sun Over 700 times more massive than rest of bodies in solar system Mostly hydrogen and helium (from spectroscopy) Fusion of hydrogen into helium creates heat & light

The Planets and Sun to scale Figure 7.3

Measuring a planet Figure 7.5 Observe motion of a satellite orbiting planet. Determine satellite’s distance (a) from planet and orbital period, P. Use Newton’s form of Kepler’s third law. Insert measured values of a and P, and value for constant G. Solve for M. Average density () is mass (M) divided by volume (V ) Measure angular size of planet and use relation between angular size and distance to solve for R. For a spherical planet of radius R

Mercury, Venus, Earth, Mars Smaller Thin or no atmosphere Inner Planets Mercury, Venus, Earth, Mars Smaller Thin or no atmosphere Made of rock w/ iron rich cores

Jupiter, Neptune, Saturn and Uranus Same core 70% hydrogen Outer planets Jupiter, Neptune, Saturn and Uranus Same core 70% hydrogen No solid surface, massive atmospheres, covered in oceans

Sketches of the interiors of the planets Figure 7.6

Photo of an interstellar cloud Figure 7.7

Origin(4.5 Billion years ago) Disk shaped cloud of gas & dust rotates & is collapsed by gravity Heat generated in center and fusion occurred (Sun) Dust particles stick together to form planets(accretion)

4. Outer planets become bigger due to lower temperature (water condensation) 5. Outer planets were massive and drew in Hydrogen & Helium from gravitational attraction (atmosphere)

Interstellar cloud Figure 7.8 A B

Condensation of dust grains Figure 7.10

The birth of planets Figure 7.11 A B

Craters on planets and moons Figure 7.12 Diane Mercury Manicouagan Crater on Earth Mars Enceladus

Craters on planets and moons, continued Figure 7.12 Tethys Titania

Newly discovered planetary systems Figure 7.13

Rules to be a “planet” Orbit the Sun Have enough Gravity to round it Not be a satellite (orbit another nonstar body) Dominate its own orbit*

Pluto falls short on the last one Pluto falls short on the last one. Astronomers started finding bodies the same size as Pluto. They felt they had to limit the amount of planets. Our Solar System has eight. Pluto is a classified a dwarf planet.