2/3/20091Remaining Remaining Solar System Solar System TopicsTopicsPSC 203PSC 203OverviewOverview Topics to be covered: Extrasolar Planets The Search for Life The Planet Debate Answers to Student QuestionsWhat is an Exoplanet?What is an Exoplanet?An exoplanet is a planet that orbits a star outside our solar systemHow Many Exoplanets Are There?How Many Exoplanets Are There? Or How many have we found…Or How many have we found… As of May As of May 11, , 20082008: :  287 287 planets orbiting planets orbiting 248 248 starsstars As of Feb As of Feb 22, , 20092009: :  336 336 planets orbiting planets orbiting 285 285 starsstars http:/planetquest.jpl.nasa.govhttp:/planetquest.jpl.nasa.govHow do we find them?How do we find them? Look for affect on starsLook for affect on stars Transit eclipseTransit eclipse Shifting star positionShifting star position Doppler Shift or Proper Motion Doppler Shift or Proper Motion  Direct Imaging ???Direct Imaging ??? Gravitational LensingGravitational LensingExoplanet PropertiesExoplanet Properties Mostly Large, Gas giantsMostly Large, Gas giants Many close to their starsMany close to their stars Why…Why… It is easier to find big things close to starsIt is easier to find big things close to stars Others just haven’t been foundOthers just haven’t been found2/3/20092Future workFuture work New missions to look for more Earth like New missions to look for more Earth like planets…planets… Keck InterferometerKeck Interferometer KeplerKepler SIM PlanetQuestSIM PlanetQuest Terrestrial Planet FinderTerrestrial Planet FinderThe Search for LifeThe Search for Life Means different things to different peopleMeans different things to different people Many viewpoints on the topic…Many viewpoints on the topic… What does it mean to you?What does it mean to you? Discuss with neighborDiscuss with neighbor Do you think we will find it?Do you think we will find it?Possible AnswersPossible Answers Searching for ExtraSearching for Extra--Terrestrial IntelligenceTerrestrial Intelligence Searching for simple organismsSearching for simple organisms Searching for the right conditions for lifeSearching for the right conditions for lifeRight Conditions?Right Conditions? What do you need to survive?What do you need to survive? Class brainstormingClass brainstormingWhat does life need to live?What does life need to live? Liquid waterLiquid water NutrientsNutrients(Raw materials)(Raw materials)  EnergyEnergyLife in a Variety of EnvironmentsLife in a Variety of Environments Most life forms live in “normal” range of Most life forms live in “normal” range of temperature, salinity, acidity, etc.temperature, salinity, acidity, etc. Some forms live and thrive in extreme Some forms live and thrive in extreme environments, they are called environments, they are called extremophilesextremophiles Live in boiling hot springs, freezing water, Live in boiling hot springs, freezing water, very salty, very acidic, etc.very salty, very acidic, etc.2/3/20093What can life tolerate?What can life tolerate?dividingbacteriumTransmitted light10 µm(Junge et al., 2001) –15°°°°CLife in the Solar SystemLife in the Solar System Where would we find conditions that any Where would we find conditions that any organism could survive?organism could survive? Where could we go and survive?Where could we go and survive?Terrestrial Extremophiles and Terrestrial Extremophiles and Life in the Solar SystemLife in the Solar System Studying terrestrial extremophiles Studying terrestrial extremophiles helps scientists understand what is helps scientists understand what is POSSIBLE POSSIBLE in the extreme in the extreme environments on other planets and environments on other planets and moons in the solar systemmoons in the solar systemWhere is Life Most Likely to Exist?Where is Life Most Likely to Exist?Mars?Mars?Evidence of much water in the past .Evidence of much water in the past .Past Life forms? Existing Life forms?Past Life forms? Existing Life forms?2/3/20094Jupiter’s Moon Europa?Jupiter’s Moon Europa?A frozen surface protects a saltwater ocean belowSaturn’s Moon EnceladusSaturn’s Moon EnceladusWater Geysers erupt at the surface •Surface temp –300 oF •Liquid H20 at 32 oF or warmer, just below surface•Tidal heating or radioactive decay keeps water in liquid phaseTerraformingTerraforming process of deliberately modifying an process of deliberately modifying an object’s object’s atmosphereatmosphere, , temperaturetemperature, surface , surface topographytopography or or ecologyecology to be similar to to be similar to those of those of EarthEarth to make it to make it habitablehabitable by by humans humans  discussiondiscussionThe Planet DebateThe Planet Debate Definitions Adopted by IAUDefinitions Adopted by IAU PlanetPlanet Orbits the sunOrbits the sun Large enough to form into a sphereLarge enough to form into a sphere Cleared the neighborhood of its orbitCleared the neighborhood of its orbit Dwarf PlanetDwarf Planet Orbits the sunOrbits the sun Large enough to form into a sphereLarge enough to form into a sphere Hasn’t cleared its orbitHasn’t cleared its orbitClearing Orbit ExamplesClearing Orbit Examples CeresCeres In asteroid beltIn asteroid belt Its gravity doesn’t really affect other asteroidsIts gravity doesn’t really affect other asteroids JupiterJupiter Has a lot of other objects in its orbitHas a lot of other objects in its orbit Most all are dominated by Jupiter’s gravityMost all are dominated by Jupiter’s gravityCurrent Dwarf PlanetsCurrent Dwarf Planets CeresCeres PlutoPluto ErisEris MakemakeMakemake HaumeaHaumea ~40 known but unnamed objects~40 known but unnamed objects ??? Unknown objects??? Unknown objects2/3/20095Remaining DebateRemaining Debate Historical objection view pointHistorical objection view point Geological objection view pointGeological objection view point Other objections …Other objections … Class ViewsClass Views Should Pluto still be classified as a planet? Should Pluto still be