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Solar system Get out a ½ sheet and get ready for your quizJ Weekly Schedule Today • Hw # 5 due • Quiz # 4 • The solar system! • Lecture Tutorials Thursday • Li=le more on planets • The Solar system Lab The auroras, both surrounding the north magneCc pole (aurora borealis) and south magneCc pole (aurora australis) occur when highly charged electrons from the solar wind interact with elements in the earth's atmosphere. Solar winds stream away from the sun at speeds of about 1 million miles per hour. When they reach the earth, some 40 hours aKer leaving the sun, they follow the lines of magneCc force generated by the earth's core and flow through the magnetosphere, a teardrop-‐shaped area of highly charged electrical and magneCc fields. Green -‐ oxygen, up to 150 miles in alCtude Red -‐ oxygen, above 150 miles in alCtude Blue -‐ nitrogen, up to 60 miles in alCtude Purple/violet -‐ nitrogen, above 60 miles in alCtude Planets in our solar system Proper.es of the Planets How do we know the proper.es of planets? • Distance from Sun known by Kepler’s laws. • Orbital period can be observed. • Radius known from angular size. • Masses known from Newton’s laws. • Rotation period known from observations. • Density can be calculated knowing radius and mass. Density = mass/volume Work the following problems. 1) “Rock A” has a mass of 45 g and a volume of 15 cubic cenCmeters. Calculate its density. 2) “Rock B” has a volume of 30 cubic cenCmeters and a mass of 60 grams. Calculate its density. Which sample is heavier? • A ✔ • B Which sample is more dense? ✔ • A • B 3 g/cm3 2 g/cm3 Density = mass/volume 1) Go to Appendix 3 (page A-‐4). Choose a planet in Table 3B. Calculate it’s density (in kg/m3) and then compare your results to the actual density. Volume of a sphere = 4/3πr3 (1000 m)3 = (1 km)3 2) Use your density to determine what your planet is made of. Ice = ~1000 kg/m3; Gases < 1000 kg/m3; Rocks ~3000kg/m3 Comparing Terrestrial and Jovian Planets Terrestrial planets: Mercury, Venus, Earth, Mars Jovian planets: Jupiter, Saturn, Uranus, Neptune 4.1 An Inventory of the Solar System All orbits but Mercury’s are close to the same plane. Differences between the terrestrial planets: • Atmospheres and surface conditions are very dissimilar. • Only Earth has oxygen in atmosphere and liquid water on surface. • Earth and Mars rotate at about the same rate; Venus and Mercury are much slower, and Venus rotates in the opposite direction. • Earth and Mars have moons; Mercury and Venus don’t. • Earth and Mercury have magnetic fields; Venus and Mars don’t. Planet densities/differentiation/ http://astro.unl.edu/classaction/solar.html density over time/planet characteristics Components of the solar system • 1 Star • 8 Planets • 166 Moons • Asteroids • Comets Components of the solar system • Meteoroids • Dwarf Planets • Kuiper Belt Objects Forming the solar system ~4.5 Ga • FormaCon of accreCon disk – Collapsing nebula’s gas fla=ens out because of gravity and conservaCon of angular momentum The Concept of Angular Momentum Conservation of angular momentum says that product of radius and rotation rate must be constant. Therefore, as a dust cloud collapses, its rate of rotation will increase. collapse_of_solar_nebula Forming the solar system • In the center of the nebula compression begins fusion of hydrogen into helium= SUN • ElectrostaCc and gravitaConal interacCons cause the dust and ice grains in the disk to accrete into Planetesimals The Forma.on of the Solar System Temperature in cloud determines where various materials condense out; this determines where rocky planets and gas giants form. Forming the Earth • AccreCon conCnues unCl the center is hot enough to melt the rock= magma • Earth forms and begins to differenCate via density Forming the Moon~ 4.53 ± .01 Ga • Crater the size of Mars • Melted the Earth and ejected a large part of the mantle into space • Eventually accreted into the moon Forming the Atmosphere • Three step process-‐ – VolaCle gases during cooling – Sulfur and CO2 from volcanic erupCons – Bacteria began to produce oxygen about 2.8 G • and Oceans Forming the Oceans • Earth cooled down, clouds formed and it rained Forming the Solar System Synopsis Surface features of Earth, Mars, Venus, and the Moon Interplanetary MaFer Asteroids and meteoroids have rocky composition; asteroids are bigger. Meteor- enters Earth’s atmosphere (above) Asteroid Ida with its moon, Dactyl Meteoritesurvives the fall lands on the ground What Killed the Dinosaurs? The dinosaurs may have been killed by the impact of a large meteor or small asteroid. 4.2 Interplanetary MaFer The impact of a large meteor can create a significant crater. The Barringer meteor crater in Arizona 4.2 Interplanetary MaFer The Manicouagan reservoir in Quebec Interplanetary MaFer Comets are icy, with some rocky parts. Unlike other solar system objects they aren’t confined to the elliptical Often take millions of years to orbit Solar Winds 4.2 Interplanetary MaFer The internal structure of the cometary nucleus: Dirty Snowballs AnatomyOfAComet HaleBoppNucleus http://media.pearsoncmg.com/aw/ Astroid collision/if/if.html?deepImpact 4.2 I nterplanetary M aFer The size, shape, and orientation of cometary orbits depend on their location. Huge supposed cloud of comets orbiting the sun: Oort cloud comets rarely enter the inner solar system. Meteor showers are M associated with comets – 4.2 Interplanetary aFer they are the debris left over when a comet breaks up. 4.2 Interplanetary MaFer What make’s Earth unique? 1) Plate tectonics 2) Moderate climate (greenhouse effect) 3) Abundant Liquid water Habitable zone and search for life 4.4 Planets Beyond the Solar System Many planets have been discovered in other solar systems; this figure compares two recently discovered exoplanets to Neptune and Earth. http://media.pearsoncmg.com/aw/ aw_chaisson_astronomytoday_6/videos/ ch15/ExtrasolarPlanetsTransit.html Some planets are discovered 4.4 Planets Beyond the Solar Sthrough ystem the “wobble” they create in their parent star’s orbit. http://media.pearsoncmg.com/aw/ aw_0media_astro/if/if.html? determine_star_velocty_vs_t 4.4 Planets Beyond the Solar System Others are discovered through the periodic dimming of the parent star’s luminosity. 4.4 Planets Beyond the Solar System These are the orbits of many extra-solar planets discovered so far. Most have masses closer to that of Jupiter than that of Earth. http://astro.unl.edu/classaction/ extrasolarplanets.html