Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Exploration of Io wikipedia , lookup
Exploration of Jupiter wikipedia , lookup
Earth's rotation wikipedia , lookup
Heliosphere wikipedia , lookup
Scattered disc wikipedia , lookup
Kuiper belt wikipedia , lookup
Definition of planet wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Interstellar probe wikipedia , lookup
Naming of moons wikipedia , lookup
Uranus and Neptune • Uranus: general information – – – – – – Discovered in 1781 (Herschel) Radius about 4x that of Earth Mass about 14.5x that of Earth Nearly featureless atmosphere Thin, dark rings 27 moons (Voyager 2, NASA/JPL) • Neptune: general information – – – – Discovered in 1846 Radius about 4x that of Earth Mass about 17x that of Earth Has internal heat & an active atmosphere – 13 moons (Voyager 2, NASA/JPL) Uranus and Neptune • Uranus and Neptune have nearly identical sizes and internal structures • Both appear bluish-green in color – Sunlight passes through an outer haze layer and reflects off the cloud tops below – The haze is rich in methane, which strongly absorbs red and orange light, letting blue and green light pass through • This bluish-green light is what gets reflected by the clouds below – An additional factor is blue-light scattering in the haze layer (Neptune & Triton, Voyager 2, NASA/JPL) Spacecraft Visits • Voyager 2 fly-bys – Uranus: January 1986 – Neptune: August 1989 • Hubble Space Telescope studies – Long-term monitoring of atmospheric weather patterns – Infrared imaging studies of their atmospheres, rings, and moons (HST image of Neptune and its largest moon Triton, NASA/JPL) Orbit and Rotation of Uranus • • • • Average distance from Sun: 19.2 AU Orbital period: 84 years Orbital eccentricity e = 0.05 Rotation axis tilted by about 980 – Tilted on its side in its orbital plane – Because intensity of sunlight is so weak at Uranus, and since interior of Uranus (copyright Calvin J. Hamilton) is a good insulator (holding heat), this has little effect on seasonal temperature variations Uranus Sun Orbit and Rotation of Neptune • • • • Average distance from Sun: 30.1 AU Orbital period: 165 years Orbital eccentricity e = 0.01 (nearly circular) Rotation axis tilted by 300 – Similar to Earth, Mars, and Saturn – Has seasonal pattern of solar heating similar to Earth’s • Rotational period: 16.1 hours – Has significant magnetic field – Similar to Uranus (copyright Calvin J. Hamilton) Interiors of Uranus and Neptune • Interior structures of both planets are very similar • Atmosphere composition: molecular hydrogen (H2), Helium (He), and methane (CH4) • Thick, slushy mantle of water, ammonia, and methane ices • Rocky cores about the size of Earth • Both planets lack the deep metallic hydrogen mantles found on Jupiter and Saturn because of their smaller size (pressure doesn’t get large enough) Atmosphere of Uranus • Uranus appears as a virtually featureless hazy bluish-green ball – The reason is a lack of internal heat, unlike the other gas giants – There is a lack of convection in the atmosphere maybe due to layered interior (like an onion)…? – Clouds are cold and don’t billow up above the top layer of haze – Results in a generally uniform appearance – Occasional clouds/storms seen by HST in the infrared (Voyager 2, NASA/JPL) Atmosphere of Uranus (NASA/JPL) Atmosphere of Neptune • Neptune, like Jupiter and Saturn, radiates about 2.7x as much energy as it receives from the Sun – Creates atmospheric convection and weather on Neptune • Belts and bright clouds of methane ice • Dark oval cyclonic storms (NASA/JPL) Atmosphere of Neptune (Voyager 2, NASA/JPL) Atmosphere of Neptune: Great Dark Spot • Large storm that appeared in the mid1980s and then vanished by 1995 (Voyager 2, NASA/JPL) Neptune’s Great Dark Spot (Voyager 2, NASA/JPL) Rings of Uranus (Voyager 2, NASA/JPL, copyright Calvin J. Hamilton) Rings of Uranus (Voyager 2, NASA/JPL) Rings of Uranus (Voyager 2, NASA/JPL) Rings of Neptune (Voyager 2, NASA/JPL) Rings of Neptune (Voyager 2, NASA/JPL) Pluto • General information – – – – – Discovered in 1930 (Tombaugh) Only planet not visited by a spacecraft Receives only 1/1600th the sunlight received by Earth Surface temperature of 35–45 K (–378 to –396 0F) Density suggests a rocky core surrounded by an icy mantle – Very tenuous CH4 atmosphere • Surface pressure is 100,000x smaller than Earth’s – Surface is covered with frozen N2 mixed with CH4 and traces of CO and H2O Orbit and Rotation of Pluto • Average distance from Sun: 39.5 AU • Orbital period: 248.5 years • Orbital eccentricity e = 0.25 (largest of the planets) – Closer to the Sun than Neptune for 20 years out of its orbit around the Sun • Orbital inclination: 170 • Rotation axis tilted by about 1200 – Affects views from Earth strongly (www.nineplanets.org) (copyright Calvin J. Hamilton) Charon • Pluto has one large moon: Charon – Discovered in 1978 (Naval Observatory) – Largest moon/planet size ratio in the solar system (radius of 625 km for Charon vs. 1150 km for Pluto) • Pluto and Charon experience synchronous rotation with each other – Always keep the same face toward each other (HST, NASA/JPL) Pluto and Charon Size Comparison Pluto Charon Surface of Pluto (HST, NASA/JPL, ESA) NASA’s New Horizons Mission • Launched in January 2006 • Scheduled for Pluto fly-by (first ever) in 2015 • Will be followed by encounters with objects in the distant Kuiper Belt (about 50 AU from Sun) in 2016 – 2020 • See the following website for mission details: pluto.jhuapl.edu/