Transcript Slide set 5
NATS 1311 From the Cosmos to Earth Jovian planets compared to earth NATS 1311 From the Cosmos to Earth NATS 1311 From the Cosmos to Earth Jupiter and Io From 29 million miles away. Zones- bright cloud regions, rising/ cooler gases. Belts- dark cloud regions, descending / warmer gases. Heating from interior causes cloud motions. NATS 1311 From the Cosmos to Earth Jupiter Great red spotGiant hurricane twice the size of earth. False color image to enhance cloud turbulence. NATS 1311 From the Cosmos to Earth Jupiter’s ring (artist’s sketch) 35,000 miles above cloud tops. NATS 1311 From the Cosmos to Earth Jupiter’s ring (Actual photo) 4000 miles, edge to edge. 1 mile thick. NATS 1311 From the Cosmos to Earth FIG.9.4 Figure 9.4 These diagrams compare the interior structures of the Jovian planets (shown approximately to scale). All four planets have cores equal to about 10 Earth masses or rock, metal, and hydrogen compounds, and they differ primarily in the hydrogen/helium layers that surround the cores. NATS 1311 From the Cosmos to Earth FIG. 9.2 Figure 9.2 Jupiter's interior structure, labeled with the pressure, temperature, and density at various depths. Earth's interior structure is shown to scale for comparison. Note that Jupiter's core is only slightly larger than Earth but is about 10 times more massive. NATS 1311 From the Cosmos to Earth SCIENTIFIC HIGHLIGHTS - JUPITER ATMOSPHERE: CLOUD BANDS - ALTERNATE COLORS CLOUD MOTIONS BELTS - REDDISH BROWN BANDS - COOLR ZONES - WHITE, YEEEOW BANDS - HOTTER COMPOSITION - WATER AND AMMONIA CLOUDS LIGHTNING AND AURORA OBSERVED GREAT RED SPOT: HURRICANE STORM OVER 300 YEARS OLD TWICE THE DIAMETER OF EARTH RING: 1 KM THICK, 6000 KM EXTENDED RADIALLY NATS 1311 From the Cosmos to Earth FIG.9.9 Figure 9.9 The larger satellites of the Jovian planets, with sizes (but not distances) shown to scale. Mercury, the Moon, and Pluto are included for comparison. NATS 1311 From the Cosmos to Earth GALILEAN MOONS Io: 8 volcanoes Smooth young surface Sulfur and SO2 frost Volcanoes eject sulfur material producing a ring of sulfur and O2 around Jupiter Magnetic field of Jupiter allows particles to penetrate the polar regions, producing aurora NATS 1311 From the Cosmos to Earth FIG. 9.11 Figure 9.11 Io is the most volcanically active body in the solar system. (a) An erupting volcanic plume rising hundreds of kilometers above Io's surface. (b) The reddish color of the nowcooled lava flows extending from this volcano on Io (center black dot) suggests they were once molten sulfur. (c) This enhancedcolor photo shows fallout (dark patch) from a volcanic plume on Io. The fallout region covers an area the size of Arizona. (The orange ring is the fallout from another volcano.) NATS 1311 From the Cosmos to Earth Io Close-up of surface. Tidal heating causes melting under surface to produce volcanoes. NATS 1311 From the Cosmos to Earth FIG. 9.12 Figure 9.12 Tidal heating explained. (a) Because Io's orbit is slightly elliptical, the strength and direction of Io's tidal bulges change. The bulges and orbital eccentricity are exaggerated. (b) About every seven Earth days (one Ganymede orbit, two Europa orbits, and four Io orbits), the three moons line up as shown. The small gravitational tugs repeat and make all three orbits slightly elliptical. NATS 1311 From the Cosmos to Earth GALILEAN MOONS EUROPA: Thin ice crust Fracture/ridge system Few craters NATS 1311 From the Cosmos to Earth FIG. 9.14 Figure 9.14 Europa is one of the most intriguing moons in the solar system. (a) Europa's icy crust is criss-crossed with cracks. (b) Some regions show jumbled crust with icebergs, apparently frozen in slush. This figure combines lowresolution images and high-resolution close-ups from the Galileo spacecraft. (c) Close-up photos show that many surface cracks have a double-ridged pattern. NATS 1311 From the Cosmos to Earth GALILEAN MOONS GANYEMEDE: Bright, young ray craters Impact basin Dark regions are heavily cratered Variety of geologic processes observed (e.g. crustal motion) Largest of the moons NATS 1311 From the Cosmos to Earth FIG. 9.15 Figure 9.15 Ganymede, the largest moon in the solar system. (a) Ganymede's numerous craters (bright spots) show that its surface is older than Europa's (b) The brighter, ridged regions of Ganymede's surface, called grooved terrain, have few craters and indicate relatively recent geological activity. NATS 1311 From the Cosmos to Earth GALILEAN MOONS CALLISTO: Ancient heavily cratered surface Impact basins Density low Little crustal motion NATS 1311 From the Cosmos to Earth FIG. 9.16 Figure 9.16 Callisto shows no evidence of volcanic or tectonic activity. (a) Heavy cratering indicates an ancient surface. (b) Close-up photos show a dark powder overlying the low areas of the surface. NATS 1311 From the Cosmos to Earth Callisto Large impact basin. Rings are shock waves that froze quickly after impact. NATS 1311 From the Cosmos to Earth NATS 1311 From the Cosmos to Earth Saturn- Ring structure Tilt of rings 27 degrees from orbital plane. NATS 1311 From the Cosmos to Earth Saturn CloudsBelts and zones not as pronounced as on Jupiter NATS 1311 From the Cosmos to Earth Saturn ring structure- false color image Cassini division- large gap in rings NATS 1311 From the Cosmos to Earth FIG. 9.22 Figure 9.22 (a) The largest gap in Saturn's rings, called the Cassini division, is caused by an orbital resonance with the moon Mimas. (b) Another Mimas resonance creates remarkable ripples in Saturn's rings. The dark spots in the image are calibration marks for the camera. NATS 1311 From the Cosmos to Earth Spokes in B ring Spokes do not follow Kepler’s Laws Magnetic and electric fields form these patterns. NATS 1311 From the Cosmos to Earth Another view of rings NATS 1311 From the Cosmos to Earth Titan, moon of Saturn 3200 miles diameter Atmosphere denser than earth’s. Nitrogen with some Methane. Temperature on surface: -180 deg. C. NATS 1311 From the Cosmos to Earth Comparison of earth and Titan atmospheres NATS 1311 From the Cosmos to Earth Fig. 9.17 Figure 9.17 Saturn's moon Titan. (a) Titan is enshrouded by a hazy, cloudy atmosphere. (b) Artist's conception of the surface of Titan, showing the possible ethane oceans. (c) A recent image from the Keck Telescope taken at infrared wavelengths can see through Titan's clouds to the surface. The dark areas may be oceans. NATS 1311 From the Cosmos to Earth SCIENTIFIC HIGHLIGHTS - SATURN SATURN: Atmosphere similar to Jupiter Dark belts and light zones High winds - 4 to 5 times faster than Jupiter’s Cold temperatures (90 k) Aurora Radio emissions RINGS: Hundreds of ringlets F ring - 3 separate intertwined ringlets: also clumps B ring has long radial spoke-like features NATS 1311 From the Cosmos to Earth SATURN’S SATELLITES: 23 (9 major moons) Number 13 and 14 guard the f ring Number 15 is on the outer edge of the a-ring Titan: • Smaller than Ganymede, larger than Mercury • Has a dense, hazy atmosphere of nitrogen (methane) and carbon dioxide with small concentrations of hydrocarbons • Surface temperature is 100 k (-170°c) • Liquid nitrogen or methane lakes may exist at the poles NATS 1311 From the Cosmos to Earth NATS 1311 From the Cosmos to Earth True (left) and false colors images of Uranus Picture of south pole from 9 million miles away. South pole, pointed toward sun. Methane in atmosphere absorbs red light; hence blue color. Discovered in 1781 by Wm. Herschel. NATS 1311 From the Cosmos to Earth Artist’s sketch of Uranus’ ringsdiscovered be stellar occultation. Rings closer to planet than moons. NATS 1311 From the Cosmos to Earth Ring structure Of Uranus. Shows dust in ring system. Streaks are stars. NATS 1311 From the Cosmos to Earth Miranda, Moon of Uranus Cosmic museum Many unique features. “7” Trapezoidal region. Grooved terrain. NATS 1311 From the Cosmos to Earth Miranda Mountainous region. NATS 1311 From the Cosmos to Earth SCIENTIFIC HIGHLIGHTS - URANUS Discovered by William Herschel in 1781 4 times earth's diameter First planet not known to Greek astronomers Blue-greenish appearance,with rocky core Thick hydrogen atmosphere with methane clouds Methane absorbes red light Rotation period 16.5 hours NATS 1311 From the Cosmos to Earth URANUS (continued) Spin axis tipped at 82° to the orbital plane Has a retrograde rotation Has a 21 year winter and a 21 year summer Poles have the same temperature Magnetic field is 50 times the earth's tipped 60 degrees NATS 1311 From the Cosmos to Earth URANUS (continued) RINGS: 10 rings 9 discovered by stellar occultation 1 discovered by Voyager spacecraft Probably composed of rocks rather than ice Source may have been a moon destroyed by a meteoroid impact NATS 1311 From the Cosmos to Earth URANUS (continued) MOONS: 5 largest seen from earth; made of rocks and ice 10 discovered by voyager spacecraft Miranda—many unique surface features, Chevron, grooved terrain, large valley, high cliffs NATS 1311 From the Cosmos to Earth NATS 1311 From the Cosmos to Earth Neptune Methane absorbs red light, gives blue-green color. Great dark spot, like Jupiter’s red spot. Cloud structure has belts and zones, like Jupiter. NATS 1311 From the Cosmos to Earth Neptune’s great dark spot. About size of earth. Same relative size to planet as Jupiter’s spot is to Jupiter. Atmosphere is very cold: -350°F Scooter- cloud formation below the dark spot. NATS 1311 From the Cosmos to Earth Neptune’s rings 50,000 Km above planet. Clumpy, not continuous. Probably methane ice. NATS 1311 From the Cosmos to Earth Triton, moon of Neptune. Probably a captured asteroid. Polar cap, frozen nitrogen. Wrinkled surface, like Mercury NATS 1311 From the Cosmos to Earth Close-up of Triton’s surface . 70% rock; 30% water ice. Very old craters. Circular region may be volcano caldera. NATS 1311 From the Cosmos to Earth Triton’s surface. The flat regions in this close-up photo may be lava-filled impact basins similar to the lunar maria. NATS 1311 From the Cosmos to Earth SCIENTIFIC HIGHLIGHTS - NEPTUNE Discovered in 1845 using mathematical analysis of Uranus' orbit Similar in size to Uranus, but slightly more dense Seeing Neptune is like seeing a dime a mile away Has a blue-green appearance (methane in atmosphere) Internal heating like Jupiter Great dark spot, not permanent Cloud features seen in atmosphere Cloud shadows indicate lower atmosphere is clear NATS 1311 From the Cosmos to Earth SCIENTIFIC HIGHLIGHTS - NEPTUNE RINGS: Has a system of thin dark clumpy rings Two thin and two broad rings 50,000 and 60,000 km above planet Probably methane ice 8 MOONS: 2 found from earth 6 discovered by voyager spacecraft NATS 1311 From the Cosmos to Earth NEPTUNE’S MOONS Triton Largest moon of Neptune: Orbits Neptune in retrograde direction probably a captured asteroid Slightly smaller than our moon Has a few craters in the southern region Has nitrogen frost at poles Atmosphere of nitrogen with traces of methane (much less dense than earth's) NATS 1311 From the Cosmos to Earth FIG. 9.23 Figure 9.23 Four ring systems. The planets are not shown to scale. Uranus's rings were photographed by the Hubble Space Telescope, the others by Voyager. The Neptune frame is made of two images, taken on either side of the bright planet. NATS 1311 From the Cosmos to Earth . NATS 1311 From the Cosmos to Earth . NATS 1311 From the Cosmos to Earth . The orientation of Pluto's spin axis and Charon's orbit. Like Venus and Uranus, Pluto has its rotation axis tipped over so far that it points below the plane of the planet's orbit (which is itself tipped by an unusually large angle, 17°, relative to the ecliptic). Thus the spin of the planet is technically retrograde (i.e., backwards). Charon orbits in the equatorial plane of the planet. During the late 1980s, the plane of Charon's orbit was aligned with thePluto-Earth direction so that Pluto and Charon alternately passed in front of each other. Observations of these repeated transit events provided a wealth of information on the nature of both bodies and the transient atmosphere of Pluto. NATS 1311 From the Cosmos to Earth . SCIENTIFIC HIGHLIGHTS - PLUTO Discovered in 1930 by Clyde Tombaugh at Lowell Observatory Not a planet that perturbs Uranus' orbit - too small Orbit has a 17º inclination to the ecliptic Elliptical orbit which passes inside the orbit of Neptune (November 1978 to may 2000) Rocky core with methane and water ices, also nitrogen ice on surface NATS 1311 From the Cosmos to Earth . SCIENTIFIC HIGHLIGHTS - PLUTO Tenuous atmosphere of nitrogen and methane May be an escaped moon of Neptune or may be one of group of icy/rocky bodies in the outer solar system. Some orbit the Jovian planets and one, Pluto, orbits the sun Moon: Charon—1978 discovery Synchronous rotation with Pluto Only 20,000 km from Pluto Half the size of Pluto 10% mass of Pluto NATS 1311 From the Cosmos to Earth . PROPERTIES OF THE SUN Diameter: 864,000 miles Volume: 1 million times that of the earth Mass: 330,000 times mass of earth Composition: Hydrogen Helium Other By mass 75% 24% 1% By volume 90% 9% 1% NATS 1311 From the Cosmos to Earth . SUN Surface temperature: Color: 5700 k (5400º C) yellow Rotation period: 25 days at the equator 33 days near poles Apparent magnitude: - 26.7 Absolute magnitude: + 4.8 NATS 1311 From the Cosmos to Earth LUMINOSITIES Luminosity: ~ r2T4 Apparent magnitude: Apparent brightness of a celestial body based on a logarithmic scale of luminosity. Magnitude scale: 1 is 2.5:1 2 is 6.3:1 5 is 100:1 Absolute magnitude: Equivalent to the apparent magnitude if star were placed 10 parsecs (32.6 light years) from sun. NATS 1311 From the Cosmos to Earth . NATS 1311 From the Cosmos to Earth . REGIONS OF SUN Photosphere: Bright disk Chromosphere: Thin, tenuous layer right above photosphere, several thousand km thick Corona: Rarefied outer region of sun's atmosphere, millions of km thick NATS 1311 From the Cosmos to Earth . FEATURES OF THE SUN Photosphere Granules Mottled texture of surface caused by convection of hot gases Gases flowing out - brighter areas Gases flowing in - darker areas NATS 1311 From the Cosmos to Earth FIG. 12.4 Figure 12.4 The basic structure of the Sun. NATS 1311 From the Cosmos to Earth FIG. 12.2 Figure 12.2 Gravitational equilibrium in the Sun: At each point inside, the pressure pushing up balances the weight of the overlying layers. NATS 1311 From the Cosmos to Earth . FEATURES OF THE SUN Photosphere Granules Mottled texture of surface caused by convection of hot gases Gases flowing out - brighter areas Gases flowing in - darker areas Sun spots Dark areas - size of earth Average lifetime of 6 days Regions of strong magnetic field NATS 1311 From the Cosmos to Earth FIG. 12.3 Figure 12.3 This photo of the visible surface of the Sun shows several dark sunspots. NATS 1311 From the Cosmos to Earth FIG. 12.17 Figure 12.17 (a) This graph shows how the number of sunspots on the Sun changes with time. Note the approximately 11year cycle. (b) This graph shows how the latitudes at which sunspot groups appear tend to shift during a single sunspot cycle. NATS 1311 From the Cosmos to Earth FIG. 12.10 Figure 12.10 Granulation of the photosphere is evident in this photo of two sunspots. Each white granule is the top of a rising column of hot gas. At the darker lines between the granules, cooler gas is descending below the photosphere. NATS 1311 From the Cosmos to Earth FIG. 12.13 Figure 12.13 Pairs of sunspots are connected by tightly wound magnetic field lines. NATS 1311 From the Cosmos to Earth FIG. 12.18 Figure 12.18 The Sun rotates more quickly at its equator than it does near its poles, a behavior known as differential rotation. Because gas circles the Sun faster at the solar equator, it drags the Sun's north-south magnetic field lines into a more twisted configuration. The magnetic field lines linking pairs of sunspots, depicted here as green and black blobs, trace out the directions of these stretched and distorted field lines. NATS 1311 From the Cosmos to Earth . Chromosphere Spicules Spiked nature of chromosphere Prominences Rosy tongues of gas up to 30,000 km high Chromospheric gases seen in corona Plages Bright areas near sunspot regions Hotter gases NATS 1311 From the Cosmos to Earth FIG. 12.14 Figure 12.14 This photo shows a large solar prominence, many times the size of Earth, which consists of glowing gas trapped by magnetic field lines arching high above the surface of the Sun. NATS 1311 From the Cosmos to Earth . Flares Brighter areas in plages Emit radiation in x-ray band Disrupt radio communications Cause aurora Corona Solar wind Streaming electrons and ions originating from Corona regions called coronal holes. NATS 1311 From the Cosmos to Earth FIG. 12.16 Figure 12.16 An X-ray image of the Sun reveals the corona: Brighter regions of this image correspond to regions of stronger X-ray emission. (Because X rays do not penetrate Earth's atmosphere, photos like this one must be taken from space.)