LEARNING ABOUT THE OUTER PLANETS Can see basic features through Earth-based telescopes. Hubble Space Telescope especially useful because of sharp imaging. Distances from Kepler s 3 rd law, diameters from angular size and distance. Masses from orbits of moons, more recently (and accurately) from gravitational effects on spacecraft. Space probes: Pioneer 10 to asteroid belt and Jupiter (launched 1972). Pioneer 11 to Jupiter and Saturn (launched 1973). Voyager 1 to Jupiter and Saturn (launched 1977). Voyager 2 to Jupiter, Saturn, Uranus, and Neptune (launched 1977). Galileo orbiter to Jupiter (launched 1989, crashed into Jupiter in September 2003 ). Cassini orbiter to Saturn (launched 1997, reached Saturn July 2004) Huygens probe landed on Titan; Jan 14, 2005 New Horizon launched Jan 19, 2006, will fly by Pluto in July 2015 NASA's Cassini spacecraft Io Above Jupiter s Clouds on New Year's Day, 2001 Credit: NASA/JPL/University of Arizona
Jupiter s Winds Jupiter Polar Winds NASA's Cassini spacecraft When is it possible to see Jupiter in the night sky? Orbital Data Configurations: Conjunction Opposition ~13 months Appears in a different zodiacal constellation every year Planet viewing in 2006 at opposition early May behind Sun Oct - Nov returns to view - December Orbital data Average distance 5.45 AU 4.95 AU Eccentricity of orbit 0.048 Orbital speed 13.1 km/s Orbital period 11.9 yrs Rotational period equatorial 9 h 50 min 28 sec polar 9 h 55 min 29 sec Inclination of orbit to ecliptic 1.3 deg Inclination of axis to orbit 3.12 deg
Basic characteristics of Jupiter Shape Size equatorial diameter 11.2 Earth s diameters polar diameter - 10.5 Earth s diameters Mass - 318 Earth s masses Density Surface gravity Temperature -162 o F Jupiter s satellites Jupiter s satellites as seen by Galileo (1610) 4 large satellites (Galilean) 62 natural satellites: 25 of them discovered recently Rings discovered in 1979 by Voyager 1 spacecraft 11 12
The Galilean Satellites of Jupiter Galileo Galilei (1564-1642) The beginning of modern physics. Strong supporter of the heliocentric model How do we measure the diameter of Jupiter The Small Angle Equation Angular size Actual size Actual distance D = ϑ d 206265 photo Used the telescope to provide evidence that the planets orbit the Sun Discovered the phases of Venus, the moons of Jupiter, the sunspots on the Sun, the mountains on the Moon 13 Example: On November 28, 2000, Jupiter was 609 million kilometers From Earth. Jupiter angular diameter on that date was 48.6 arcsec. Using the small-angle equation, calculate Jupiter s diameter. ϑ d 48.6 609000000 km D = = = 143000 km 206265 206265 R R V V J E J E 71500 = = 11 6700 3 71500 3 = = 11 = 1330 3 6700 Rotational period equatorial 9 h 50 min 28 sec polar 9 h 55 min 29 sec Rotation of Jupiter How do we measure the rotational period? Jupiter is not a solid object differential rotation Independent way of calculating the diameter Doppler Effect
How do we calculate the mass of Jupiter Newton s version of Kepler s empirical law: P 2 3 4π a = G( m + M ) ~ M Jupiter is much larger than m Satellite. ~ Units: P - in seconds, a - in meters. 2 Jupiter s Atmosphere Colorful bands Red, brown, orange, yellow Belts Zones Great Red Spot Origin Age Rotation Size: 3Earths 17 18 Jupiter s Atmosphere Great Red Spot White ovals Origin Preferable location Brown ovals Origin Preferable location 19 High Pressure Gas flows outward 20
Dark Ovals White Ovals High Pressure Short living, Earth s size 21 Fig. 12.13 Low Pressure Short living, Earth s size 22 Belt and Zone Structure Infrared and visible images of Jupiter Strong convection Brings to the surface layers from different depth which have different color Bright infrared regions are relatively warm Dark infrared regions are relatively cool 23 Dark features are warmer and deeper Rotation shapes belts and zones into bands parallel to the 24 equator 6
Great Red Spot High Pressure Gas flows outward Dark but high and cool Exception! 25 26 Jupiter s structure Density 1.33 g/ c cm, mostly hydrogen and helium, no real hard surface on Jupiter Deeper into the atmosphere, the gases just get denser Pressure large liquid H and He Pressure so great - that the hydrogen atoms are tightly packed together, collide frequently with each other; these collisions strip the electrons off the atoms, leaving protons surrounded by loose electrons: liquid metallic hydrogen Strong electric currents - strong magnetic field Small rocky core that keeps the entire planet less oblate than it would be otherwise Evolution: the rocky core could form first, then attract the gas. 27 Jupiter s atmosphere Composition of upper atmosphere 86.2 % hydrogen 13.6 % helium 0.2% methane, ammonia, water vapor Clouds Deep inside expect more He, less H Composition of lower atmosphere H & He at high temperature and pressure: liquid phase 28
Jupiter s structure Based on models Can probe the upper ~200 km Atmosphere gaseous H & He liquid H & He Liquid Metallic H Layers of water, methane, ammonia Rocky core Jupiter s structure Deep inside it should be very hot and very dense. Models give: pressure at center roughly 80 million atmospheres temperature at center roughly 22,000 F Jupiter has a big magnetic field angular size of magnetosphere 29 30 Jupiter s magnetosphere Jupiter emits 2.5 times more radiation than it absorbs from the Sun Planet slowly contracting, generating heat from gravitational energy All planets in the Solar System formed from interstellar material First 10 000 yrs large and cool Then, it contracted and heated up Contraction (almost) stopped, heat to release Now it slowly releases this energy