Jane Lucas

Jane Lucas
Astronomy 100-Week 8 Lecture – Chapter 7

The topics that were covered in class were the following:
Super-Earth
Chapter 7
Super-Earth – Since 1995 Hot Jupiter’s are known outside the Solar System.  These are called Expo-planets.  They pull their central star enough to produce a sine wave of velocity.  These velocity changes are measured through the Doppler affect.  The first Super-Earth in a habitable zone was found by Stephane Udry.  These Hot Jupiter’s were not expected.  The theory of planet formation by Viktor Safronov did not predict them as studied by Alan Boss.  Our Jupiter is far from the Sun and the sine wave velocity shape is too little to see such huge distances.  Jupiter’s are more gas than solid and super earths are more solid than gas.  So far no habitable planet has been found.
Chapter 7 – Earth and the Terrestrial Planets.  Mercury has craters, smooth planes, and cliffs.  Venus has volcanoes with few craters.  Mars has some craters and has the biggest volcano in the solar system.  Moon has craters with smooth plains.  Earth has volcanoes, craters, mountains, and riverbeds.  
Earth is geographically active because of its rocky crust, mantle, metal core, and rigid lithosphere.  Earth’s interior is a core, mantle, and crust.  
Differentiation-Gravity pulls high density material to center.  Lower density material rises to the surface.  
Lithosphere-A planet outer layer of cool rigid rock called the lithosphere.  Its floats on the warmer, softer rock, that lies beneath. 

Strength of Rock – Rock stretches when pulled slowly but breaks when pulled rapidly.  
Heat drives geological activity.  Convection is when hot rock rises, cools rock falls.  One convection cycle takes 100 million years on earth.  Sources of internal heart are differentiation, radioactivity, and gravitation potential.  Heating of interior overtime caused accretion and differentiation when planets were young.  Radioactive decay is the most important heat source today.  Cooling of interior by convection, conduction, and radiation sends energy into space.  
The Surface Area-to-Volume Ratio= surface area/volume.
Heat contents depend on volume.  Loss of heat through radiation depends on surface area.  Time to cool depends on surface area divided by volume.  
Planetary magnetic fields are moving charged particles that create magnetic fields.  A planet’s interior can create magnetic fields if its core is electronically conducting, convecting, and rotating.  
Earth’s Magnetosphere-Earth’s magnetic field protects us from charged particles from the Sun.  The charged particles can create an aurorae (Northern Lights).
P waves push matter back and forth.  S waves shake matter side to side.  
The processes that shape Earth surface are impact catering, volcanism, tectonics, and erosion.  Impact catering is 10 times wider than the objects that made them.  
Radiation protection is when all x-ray light is absorbed very high in the atmosphere.  Ultraviolet light is absorbed by the ozone.
Earth’s atmosphere absorbs light at most wavelengths.
A Greenhouse Gas is CO2, H2O, CH4, and any gas that absorbs infrared.  Due to the Greenhouse Effect Earth is much warmer than Venus.  
Earth retains plenty of internal heat because of its larger terrestrial planet.
Earth’s unique features that are important for life are: surface liquid water, atmospheric oxygen,  plate tectonics, and climate stability.  Earth’s distance from the Sun and moderate greenhouse effect make liquid water possible. Photosynthesis (plant life) is required to make high concentrations of O2, which produces the protection layer of O3. Plate tectonics is an important step in the carbon dioxide.  The CO2 cycle acts like a thermostat for Earth’s cycle.  
Continental Motion-Idea of continental drift was inspired by a puzzle like fit of continents.  Mantle material erupts.  
Seafloor is recycling through a process known as subduction.  
Plate Motions-Measurements tell us past, present, and future layout of continents.  
Carbon Dioxide Cycle: 1) Atmospheric CO2 dissolves in rainwater. 2) Rain erodes minerals that flow into the ocean. 3) Minerals combined with carbon to make rocks on ocean floor.
4) Subduction carbonate rocks down on the mantle. 5) Rock melts in mantle and out gases CO2 back into atmosphere through volcanoes. 
Long term climate change is changes in Earth’s axis tilt might lead to ice ages.  Widespread ice tents to lower global temperatures by increasing Earth’s reflectivity.  CO2 from out gassing will build up if oceans are frozen.  
Global warming is human activity changing our planet.  Humans made CFC’s in the atmosphere and it destroyed the ozone reducing protection from UV radiation.  Human activity is driving many other species into extinction. Humans use of fossil fuels produce greenhouse gases that can cause global warming. Earth’s average temperature has increased by 0.5 ° C in the past 50 years.
The concentration of CO2 is rising rapidly. An unchecked rise in greenhouse gases will eventually lead to global warming.  
CO2 Concentration-Global temperatures have tracked CO2 for the last 500,000 years.  Antarctic air bubbles that indicate the current CO2 concentration is at the highest level in at least 500,000 years.  Most of the CO2 has increased in the last 50 years. 
What makes a planet habitable – Located at an optimal distance from the Sun for liquid and water to exist.  Large enough for geological activity to release and retain water and atmosphere.  
Earth is habitable because it is large enough to remain geologically active.
In chapter 7 we learned about the terrestrial worlds.  A planet’s distance from the Sun makes a significant difference to the surface temperature.  The greenhouse effect makes a difference in our atmosphere.  The consequences were discussed on global warming with human activity.