Quiz 4 Recap 17 November 2011

Sunspots are cooler than their surroundings. Magnetic fields suppress rising hot gas in the convective zone

All planets orbit the Sun in the same direction in approximately the same plane.

How do we know the temperature of the Sun’s photosphere is 5,800 K? Spectroscopy and Wien’s Law Stefan Boltzmann LawLuminosity/Radius/Temp Equation If you know R & L, can find T L = 4πR2σT4 Wien’s Law:

Inner Planets are Rocky Thin crust Generally thick, rocky (silicate) mantle Iron/Nickle core Chemical composition similar to Sun for elements heavier than Hydrogen or Helium Low mass Dense Thin atmosphere

Outer or Jovian Planets All the Jovian planets are larger than the Terrestrial planets. All have similar compositions and are similar to the Sun. Solar composition is mostly Hydrogen, some Helium, etc. All have low average densities, All have rings and many satellites. None have surfaces but only increasingly dense atmospheres and rock and metal cores. High mass Thick atmosphere

Outer Planets are More Massive The heat from the Sun prevents ices from reforming on the dust grains in the region near the Sun. Ices condensed only in the outer parts of the Solar nebula. In the inner portion of the disk only materials like iron and silicates (rock) can condense into solids. Slowly they form clumps of material. In the outer portion of the disk much more material can condense as solids including ice. This extra material allows clumps to grow larger and faster. Both rock and ices (water, methane, ammonia) may form in the outer solar system. Since hydrogen is the most abundant element in the solar nebula, and it condenses at lower temperatures, there is more planet building material in the outer solar system.

Outer Planets are More Massive The most abundant atom in the universe is hydrogen In our solar system, molecules with hydrogen may condense (change from gas to liquid or solid [ice]) only in the cool outer regions. Therefore, there is more planet building material in the outer solar system. Both rock and ices (water, methane, ammonia) may form in the outer solar system. Since hydrogen is the most abundant element in the solar nebula, and it condenses at lower temperatures, there is more planet building material in the outer solar system.

Outer or Jovian Planets All the Jovian planets are larger than the Terrestrial planets. All have similar compositions and are similar to the Sun. Solar composition is mostly Hydrogen, some Helium, etc. All have low average densities, All have rings and many satellites. None have surfaces but only increasingly dense atmospheres and rock and metal cores.

Venus is the Hottest Inner Planet When the gases in an atmosphere allow sunlight to strike the surface the surface heats up and gives off infrared radiation. If the atmosphere however prevents the infrared radiation from radiating back out to space the temperature of the planet can increase, this is the Greenhouse Effect. Carbon Dioxide CO2 behaves this way and is an important greenhouse gas. Venus’ atmosphere is 95% CO2.

Why is Earth’s Atmosphere so Different from Mars’ and Venus’? Water + CO2 makes carbonic acid = soda water Rain on Earth removes CO2 from the atmosphere and locks it into the rocky ground Venus’ atmosphere is too hot for water to condense out  no water rain to remove CO2 Mars’ atmosphere is too thin and cold for water rain (may have fog) Mars does have CO2 snow at poles Mars currently has very little water in its atmosphere

Why is Earth’s Atmosphere so Different from Mars’ and Venus’? Role of Biology on Earth Plants use carbon-dioxide to make cellulose Sea creatures use carbon-dioxide runoff (from rain) to make shells (calcium carbonate). Plants break down water and carbon dioxide by photosynthesis, releasing oxygen into the atmosphere Geological processes melt rock in the hot mantle re-releasing carbon-dioxide into the atmosphere

Surface Geological Activity on Earth is driven by Heat in its Interior

Solar Granules Top layer of convective zone 14 14

Earth’s Interior The thin crust of Earth rides on an elastic layer of rock called the mantle. Below the mantle lies the liquid outer core composed of iron and nickel At the center is the solid inner core also composed of iron and nickel Motions within the mantle cause the crust to be dragged along. The crust is broken up into “plates” that shift around causing earthquakes, volcanoes and forming mountain ranges

Even colder Uranus and Neptune have top layers of mostly methane, giving a blue, mostly featureless appearance. Jupiter’s (cool) atmosphere has a mix of methane, ammonia and water. Saturn’s (cooler) atmosphere has a top layer of ammonia ice crystals, giving it a beige visible color with some bands.

Saturn Neptune Uranus When viewed in infrared light, which penetrates the top layers of the atmosphere, the remaining outer planets reveal wind-shear bands and storms (bright, or hot spots) similar to those observed on Jupiter in visible light images.

New Infrared Images of Saturn from Cassini Clockwise from upper left: Dec 2010 / Jan 2011 / Feb 2011 (11 hours apart)

Einstein’s Mass-Energy Relation In 1905 Albert Einstein recognized that mass and energy were related through the formula: E=mc2 (m =mass, E=energy, c=speed of light) What this means is that a small amount of mass could be converted into an enormous amount of energy. The means by which the Sun generates this energy is through nuclear fusion. Albert Einstein (1879-1955)

Nuclear Fusion The specific steps of nuclear fusion follow a process called the proton-proton chain Through this process 2 neutrinos, 2 positrons, 2 1H and a 4He is created by the fusion of 6 1H. The mass of all the particles created is less than the sum of the masses of colliding particles. This difference in mass was converted into energy through E=mc2.

Hydrostatic Equilibrium Requires that the pressure generated by the fusion reactions in the core of the Sun must be in exact balance with the weight of material falling inwards due to the Sun’s gravity. Without this balance the Sun would either collapse (gravity wins) or explode (pressure wins). 21 21