Astronomy 100 Exploring the Universe Tuesday, Wednesday, Thursday Tom Burbine [email protected] Composition of the PlanetsDifferent bodies have different densitiesLife of a StarSlide Number 5CondensingProtostarSlide Number 8When does a protostar become a starSlide Number 10Formation of Solar SystemCompositionSlide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21If you want to find life outside our solar systemExtrasolar PlanetsStar NamesStar Names nowOur Solar System has basically two types of planetsThings to RememberQuestion:What is the problem when looking for planets?What is the problem when looking for planets?Slide Number 31Slide Number 32So what characteristics of the planets may allow you to “see” the planetSo what characteristics of the planets may allow you to “see” the planetSlide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39Some Possible Ways to detect PlanetsCenter of MassRadial Velocity (Doppler Method)Slide Number 43Slide Number 44Slide Number 45BiasBiasTransit MethodSlide Number 49One major problemSlide Number 51Direct ObservationSlide Number 53Slide Number 54Slide Number 55How did these Hot Jupiters get orbits so close to their stars?How did these Hot Jupiters get orbits so close to their stars?Kepler MissionKepler MissionKepler MissionSlide Number 61Slide Number 62Slide Number 63Slide Number 64Slide Number 65Any Questions?Astronomy 100Exploring the UniverseTuesday, Wednesday, ThursdayTom [email protected] of the PlanetsDifferent bodies have different densities• Density = Mass/Volume• M = 4π2d3/GP2V =4/3πR3Life of a Star• A star-forming cloud is called a molecular cloud because low temperatures allow Hydrogen to form Hydrogen molecules (H2)• Temperatures like 10-50 KRegion is approximately 50 light years acrossCondensing• Interstellar clouds tends to be lumpy• These lumps tend to condense into stars• That is why stars tend to be found in clustersProtostar• The dense cloud fragment gets hotter as it contracts• The cloud becomes denser and radiation cannot escape• The thermal pressure and gas temperature start to rise and rise•The dense cloud fragment becomes a protostarWhen does a protostar become a star• When the core temperatures reaches 10 million K, hydrogen fusion can start occurringFormation of Solar System• Solar Nebula Theory (18thcentury) – Solar System originated from a rotating, disk-shaped cloud of gas and dust• Modern theory is that the Solar System was born from an interstellar cloud (an enormous rotating cloud of gas and dust)Composition• ~71% is Hydrogen• ~27% is Helium• ~2% are other elements (Fe, Si, O) in the form of interstellar grains• Show animation• Dust grains collide and stick to form larger and larger bodies. • When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity, becoming protoplanets• Protoplanets collide to form planets– Asteroids such as Ceres and Pallas are thought to be leftover protoplanets• Condensation – conversion of free gas atoms or molecules into a liquid or solid• Volatile – Elements or compounds that vaporize at low temperaturesForm atmosphere and oceansIf you want to find life outside our solar system• You need to find planetsExtrasolar Planets• Today, there are over 400 known extrasolar planets• ~463 extrasolar planets known as of todayStar Names• A few hundred have names from ancient times•Betelgeuse, Algol, etc.• Another system:• A star gets name depending on what constellation it is in• With a Greek letter at the beginning– Alpha Andromeda, Beta Andromeda, etc.• Only works for 24 brightest starStar Names now• Stars are usually named after the catalog they were first listed in• HD209458 is listed in the Henry Draper (HD) Catalog and is number 209458• HD209458a is the star•HD209458b is the first objects discovered orbiting the starOur Solar System has basically two types of planets• Small terrestrial planets – Made of Oxygen, Silicon, etc.• Large gaseous giants – Made primarily of hydrogen and a little helium– Jupiter - 90% Hydrogen, 10% Helium– Saturn – 96% Hydrogen, 3% Helium– Uranus – 83% Hydrogen, 15% Helium– Neptune – 80% Hydrogen, 20% HeliumThings to Remember• The Milky Way has at least 200 billion other stars and maybe as many as 400 billion stars• Jupiter’s mass is 318 times than the mass of the EarthQuestion:• How many of these stars have planets?What is the problem when looking for planets?What is the problem when looking for planets?• The stars they orbit are much, much brighter than the planets• Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. • GQ Lupi is 400 light years from our Solar System and the star itself has approximately 70% of our Sun's mass. • Planet is estimated to be between 1 and 42 times the mass of Jupiter. • http://en.wikipedia.org/wiki/Image:GQ_Lupi.jpgSo what characteristics of the planets may allow you to “see” the planetSo what characteristics of the planets may allow you to “see” the planet• Planets have mass• Planets have a diameter• Planets orbit the starhttp://upload.wikimedia.org/wikipedia/commons/d/de/Extrasolar_Planets_2004-08-31.png• Jupiter – H, He– 5.2 AU from Sun– Cloud top temperatures of ~130 K– Density of 1.33 g/cm3• Hot Jupiters– H, He– As close as 0.03 AU to a star– Cloud top temperatures of ~1,300 K– Radius up to 1.3 Jupiter radii– Mass from 0.2 to 2 Jupiter masses– Average density as low as 0.3 g/cm3100 1,00010(lightyears)Some Possible Ways to detect Planets• Radial Velocity (Doppler Method)• Transit Method•Direct ObservationCenter of Mass• Distance from center of first body = distance between the bodies*[m2/(m1+m2)]• http://en.wikipedia.org/wiki/Doppler_spectroscopyRadial Velocity (Doppler Method)http://www.psi.edu/~esquerdo/asp/shifts.jpg• http://astronautica.com/detect.htmhttp://www.psi.edu/~esquerdo/asp/method.htmlWavelengthwww.physics.brandeis.edu/powerpoint/Charbonneau.pptBias• Why will the Doppler method will preferentially discover large planets close to the Star?Bias• Why will the Doppler method will preferentially discover large planets close to the Star?•