CHAPTER 23 – SOLAR SYSTEM

23.1

Our solar system contains the sun, 8 planets, 3 dwarf planets, moons, asteroids, comets, and meteors – Sun takes up 99.85% of mass in solar system – Order of planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune – All planets move in ellipses around the sun & all travel in the same direction

Formed via the Nebular Hypothesis – the sun & planets formed out of a rotating cloud of gas (H & He) & dust called a nebula Nebula began to spin = gravity Began to spin faster & contracted to form planetesimals (small, irregular shaped solid bodies) that grew larger over time to form planets

2 TYPES OF PLANETS 1. TERRESTRIAL Mercury, Venus, Earth, Mars 2. JOVIAN Jupiter, Saturn, Uranus, Neptune

TERRESTRIAL PLANETS ARE: – Relatively small size – Rocky & metallic substances in core, little ice or gas – Thin atmosphere (because of smaller mass) – Located close to sun – Inner planets) – High Densities

JOVIAN PLANETS ARE: – Large size – Composed primarily of gas (H & He) & ice (NH 3, CH 4, & CO 2 ) – Small iron (Fe) cores – Thick atmosphere of H, He, methane (CH 4 ) & ammonia (NH 3 ) – Located far from sun – Outer planets) – Small Densities Gas Giants Pluto doesn’t fit into either category

OTHER OBJECTS IN THE SOLAR SYSTEM Comets – pieces of rocky & metallic materials held together by frozen gases like water vapor, methane, carbon dioxide, & carbon monoxide – Travel in elongated orbits that take up to thousands of years to complete – Glowing head = Coma – Tail forms behind as solar energy vaporizes the frozen gases (probably caused by solar wind) Tail always points away from the sun

– Haley’s Comet – orbits Earth every 76 years (next time is 2062) – Comets eventually break apart – Originate in: Kuiper Belt = region just beyond Neptune Oort Cloud = outer edge of solar system

ASTEROIDS – Asteroids – small rocky bodies – Irregular shapes – Most asteroids lie between Mars & Jupiter in an Asteroid Belt

METEOROID – small solid particle that travels through space – Shooting stars, light is caused by friction between particle & the atmosphere – Originate by: Interplanetary debris that was not accumulated into a planet when the solar system was forming Material from asteroid belt Solid remains of comets – Most are the size of sand grains & vaporize within Earth’s atmosphere = Meteors

METEOR SHOWERS – when meteor sightings reach 60 or more per hour, result when Earth encounters a swarm of meteoroids traveling in the same direction as Earth – Perseid Shower occurs each year around August 12 th – A meteoroid that reaches Earth’s surface without burning up is called a Meteorite – Create large impact craters

23.2

1. MERCURY – Innermost planet – Smallest planet (little larger than the Moon) – Surface is covered by cratered highlands (similar to the Moon) – Very dense – large iron core for its size – Quick revolution time (1 mercury year = 88 earth – slow rotation time (1 mercury day = 179 earth days) Nighttime temps = -173°C Noontime temps = 427°C – Greatest temperature extremes of any planet

2. VENUS – Second brightest object in Earth’s night sky (only the Moon is brighter) – Revolves in nearly a perfect circle (1 Venus year = 255 Earth days) – Similar in size, density, mass, & location to Earth = called “Earth’s Twin” – Thick atmosphere made of 97% Carbon Dioxide Surface pressure is 90X’s more than Earth’s because of thick atmosphere Creates a “Run-Away Greenhouse Effect” by trapping heat at surface Surface temperature = 475°C (Venus is hottest planet) – Surface features are plateaus, mountains, & huge volcanoes that covered the surface with basaltic lava that were determined by radar mapping

4. MARS Easily visible with telescope Known as the Red Planet because of rusty colored dust on surface Thin atmosphere (1% as dense as Earth’s) made of Carbon Dioxide Polar ice caps made of ice (H 2 O) & frozen carbon dioxide Temps range from -70°C to 100°C Extensive dust storms because of strong winds (270 km/hr)

MARS CON’T. Large shield volcanoes – Olympus Mons (Largest volcano in solar km high) Large canyons – Valles Marineris (Many kms. Longer than Grand Canyon), created by large faults

Possible water drainage patterns on surface similar to those on Earth Currently being explored by rovers Spirit & Opportunity 2 moons – Phobos & Deimos (captured asteroids), very small in size

OUTER PLANETS

5. JUPITER By far the largest planet (2.5 times the mass of all other planets combined) Fastest rotation (1 Jupiter day = 10 Earth hours) Appears to have alternating bands of multicolored clouds = very fast wind belts caused by high release of internal heat Great Red Spot = giant hurricane-like storm in southern hemisphere Atmosphere is made of H & He

JUPITER CON’T. Liquid surface (because of intense pressure) made of H Core is liquid metallic H Ring system made of fine dust particles 63 moons (4 are Galilean Moons): – Io = volcanically active due to the tidal energy generated by the constant tug of war between Jupiter & the other Galilean moons – Europa = smallest, icy surface (possible water beneath), will be explored for life – Ganymede = largest moon in the solar system; smooth & cratered surface – Callisto = outermost, densely cratered

6. SATURN 1 Saturn revolution = Earth years Similar in atmosphere, composition, & internal structure to Jupiter 2 nd largest planet Extensive ring system first discovered by Galileo – Consist of multiple concentric rings composed of ice & rock with gaps in between – Main Rings (A & B) are tightly packed & dense, very bright/visible – Thin outer rings are widely spaced

SATURN CON’T. Very fast wind speed in atmosphere = up to 1,500 km/hr Alternating bands of storms in atmosphere 31 moons – Titan is 2 nd largest moon in solar system & is larger than Mercury, has substantial atmosphere

7. URANUS – Unique rotation = axis of planet is at 90°, so Uranus appears to rotate on its side Thought to be caused by a giant impact that forced the planet to roll over – Faint ring system made of 9 distinct ring belts – 25 moons Miranda = Large size & varied landscape

8. NEPTUNE Very active atmosphere – constant winds at 1,000 km/hr=windiest place in solar system Atmosphere made of mostly nitrogen Large storm systems = Great Dark Spot Cirrus-like clouds occupy atmosphere, thought to be made of frozen methane (gives planet a bright blue color)

NEPTUNE CON’T. Lowest surface temperature measured yet at -200°C Faint ring system 13 known moons – Triton = largest moon of Neptune, exhibits retrograde motion (rotates opposite of Neptune) – captured asteroid – Also displays volcanic activity

PLUTO No longer the smallest planet, now called Dwarf planet Located within a swarm of other icy objects 40 times farther from the sun than Earth Slow orbital speeds, 1 year on Pluto = 248 Earth years Highly eccentric (angled orbit) – occasionally Pluto is closer to te sun than Neptune Icy world = “dirty snowball” – Temperature is estimated at -210°C 1 moon = Charon, very similar in size to Pluto – Orbits very close to Pluto (20X’s closer than our Moon)

QUALIFICATIONS FOR DWARF PLANET Must be in orbit around the Sun Has sufficient mass for its self-gravity to overcome rigid body forces so that it can assume a hydrostatic equilibrium shape (near-spherical) Has failed to clear the neighborhood around its orbit Is not a satellite

DIFFERENCE BETWEEN DWARF PLANET & PLANET – The only difference between a dwarf planet & planet is that a planet has cleared its neighborhood around its orbit 3 DWARF PLANETS IN OUR SOLAR SYSTEM – Ceres Located in the Asteroid belt between Mars & Jupiter – Pluto Located in Kuiper belt – Eris (UB313) Located in Kuiper belt