Lecture 12 - Jovian Planets

Lecture 12 - Jovian Planets - Saturn Uranus Neptune Jupiter...

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Unformatted text preview: Saturn Uranus Neptune Jupiter The Jovian Planets ASTRONOMY 3 Lesson 12 1 NATURE of the Universe Astronomy - The Jovian Planets Review of Lesson 11 A run-away greenhouse effect, caused by Venus' dense atmosphere consisting primarily of carbon dioxide, has raised the surface temperature to 730 K. Mars atmospheric composition is similar to Venus, though Mars' atmosphere is thinner. The polar ice caps on Mars are made of CO2 and water ice. Mars houses the largest volcanoes in the solar system, some of which might still be active. There is no present evidence for life on Mars. Microbial life may have been possible in the past when Mars still had a denser atmosphere and was warmer. 2 NATURE of the Universe Astronomy - The Jovian Planets Review of Lesson 11 Martian "Dust Devil" 3 NATURE of the Universe Astronomy - The Jovian Planets Today's Topics Exploration of the Jovian Planets (Ch. 7.2) Jupiter: basic properties and its atmosphere (Ch. 7.1, 7.4) Basic properties of Saturn, Uranus and Neptune (Ch. 7.3) Inner Structure of Jovian Planets (Ch. 7.6) Summary & Mid-term Exam 1 results 4 NATURE of the Universe Astronomy - The Jovian Planets Exploration Since ancient times, only 6 planets were know: Mercury, Venus, Earth, Mars, Jupiter and Saturn. In 1781, F.W. Herschel discovered the planet Uranus by chance while scanning the skies with his telescope. Deviations of Uranus' orbit from Kepler's laws were noted and explained by the presence of another outer planet. Urbain Le Verrier predicted the position of this planet. Neptune was discovered in 1846 within 1 degree of the predicted position by Johann Gottfried Galle and Heinrich d'Arrest. 5 See http://www.ucl.ac.uk/sts/nk/neptune/ for more background information on the discovery of Neptune. NATURE of the Universe Astronomy - The Jovian Planets "Top view" of the Solar System Exploration Jupiter is about 5 times the distance from the Sun than Earth (5 Astronomical Units). Neptune is almost 6 times farther away from the Sun than Jupiter (almost 30 Astronomical Units). 6 NATURE of the Universe Astronomy - The Jovian Planets Exploration Why send space probes to the Jovian planets? Hubble Space Telescope's (HST) resolution in the visual (650 nanometer): 0.05 arcsec When Earth and Jupiter are closest to each other, HST can resolve details 150 km across on Jupiter. When Earth and Neptune are closest to each other, HST can resolve detail 1,000 km across on Neptune. To study finer details, one has to get closer. 7 NATURE of the Universe Astronomy - The Jovian Planets Space probes to the outer solar system Exploration Pioneer 10 (launched 1972) was the first probe to visit Jupiter Pioneer 11 (launched 1973) and Voyager 1 (launched 1977) visited Jupiter and Saturn Voyager 2 (launched in 1977) flew a "grand tour", visiting Jupiter, Saturn, Uranus and Neptune Galileo (launched in 1989) was the first probe to orbit Jupiter Cassini (launched in 1997) was the first probe to orbit Saturn New Horizons (launched in Jan 2006) on course to Pluto, will fly-by at Jupiter in Feb 2007 8 NATURE of the Universe Astronomy - The Jovian Planets Exploration Pioneer and Voyager space probes: our 1st interstellar travelers In Aug 2006, Voyager 1 passed a distance of 100 Astronomical Units from the Sun 9 NATURE of the Universe Astronomy - The Jovian Planets Jupiter Jupiter is the largest planet in the solar system. Its diameter is around 140,000 km. 10x Earth's diameter How does this compare to Earth? How does this compare to the Sun? 0.1 x Sun's diameter 10 NATURE of the Universe Astronomy - The Jovian Planets Jupiter "Back-yard" observations of Jupiter and some of its moons over a period of 3 hours. There are light and dark bands in Jupiter's atmosphere There is circular "spot" in the southern hemisphere Jupiter is rotating fast (10 hours for one rotation) Jupiter has an "equatorial bulge", i.e. its diameter on the equator is about 6% larger than from pole to pole. This is caused by Jupiter's fast rotation. 11 The observations showing Jupiter's rotation and the orbital motion of Io and Europa (two of Jupiter's moon) have been obtained by David Haworth using a 15 cm reflecting telescope. See http://www.stargazing.net/David/jupiter/jupiter040426.html NATURE of the Universe Astronomy - The Jovian Planets Jupiter The mass of Jupiter can be derived from observations of the orbits of its moons and Newton's laws. The mass of Jupiter is 2.5 times the mass of all other planets in the Solar System combined this is about 1/1,000 the mass of the Sun this about 320 times the mass of Earth Density of Jupiter (mass divided by volume): 1,300 kg/m3 For comparison, (liquid) water has a density of 1,000 kg/m3, and Earth has a density of 5,500 kg/m3. 12 NATURE of the Universe Astronomy - The Jovian Planets Cassini "fly-by" snapshots of Jupiter Jupiter 13 NATURE of the Universe Astronomy - The Jovian Planets Jupiter Cassini monitoring of Jupiter's weather (bands, clouds, storms) over a period of 10 days (24 rotations). Jupiter's rotation has been "removed" in order to better see the dynamics of the atmosphere 14 NATURE of the Universe Astronomy - The Jovian Planets Jupiter Cassini monitoring of Jupiter's red spot (close-up) wind direction The "Great red spot" is Jupiter's largest (average size 25,000 km) and most complex storm system. It is a high-pressure system rotating counter-clockwise. 15 NATURE of the Universe Astronomy - The Jovian Planets Jupiter The "Great red spot" was first seen in 1665, and thus has been around for more than 300 years! Colors vary from pale-orange to deep red. Origin of the colors is still not understood. 16 NATURE of the Universe Astronomy - The Jovian Planets What drives Jupiter's weather pattern? Jupiter Convection transporting heat from Jupiter's interior to the surface seems to be responsible for the band structure and the storm systems Details are still under study, i.e. we cannot make weather forecasts for Jupiter, yet. 17 NATURE of the Universe Astronomy - The Jovian Planets What is Jupiter made of? Jupiter How can we find out? Low density indicates that it cannot be made of mostly of metals and rocks. Spectroscopic studies enables us to identify atoms and molecules In 1995, the Galileo atmospheric entry probe provided direct measurements of Jupiter's atmosphere 18 NATURE of the Universe Astronomy - The Jovian Planets Jupiter Hubble Space Telescope observations pin-point the target area of the Galileo atmospheric entry probe. 19 NATURE of the Universe Astronomy - The Jovian Planets Atmospheric composition of Jupiter: Jupiter Hydrogen Helium other 0.4% 13.6% Mostly hydrogen and helium, about 0.2 % methane. Very little water or oxygen 86.0% 20 NATURE of the Universe Astronomy - The Jovian Planets Structure of Jupiter's atmosphere Jupiter Atmosphere is 100 km deep from the top of troposphere. Ammonia ice exists in the top layer, water ice further down. Below 100 km depth it is too hot for ice to exist. The Galileo entry probe measured wind speeds up to 600 km/hr (or 400 miles/hr), suggesting weather is driven by heat from Jupiter's interior. 21 NATURE of the Universe Astronomy - The Jovian Planets Basic properties Comparison of the bulk physical properties of terrestrial and jovian planets Terrestrial inner solar system smaller masses and radii high density rocky, solid surface slower rotation, weak magnetic field no/few moons, no rings Jovian outer solar system larger masses and radii low density gaseous faster rotation, strong magnetic field many moons, rings 22 NATURE of the Universe Astronomy - The Jovian Planets Basic Properties (dwarf planet) (dwarf planet) 3 Terrestrial (Earth-like or rocky) planets: Mercury, Venus, Earth, Mars Jovian (Jupiter-like or gaseous) planets: Jupiter, Saturn, Uranus, Neptune 23 For comparison, the density of water is 1,000 kg/m3 - Saturn would float if you could find an ocean wide and deep enough to place it in. NATURE of the Universe Astronomy - The Jovian Planets Basic Properties Saturn has about 100 times the mass of Earth and is almost as large as Jupiter. It also shows horizontal bands in its atmosphere, but is much less colorfull than Jupiter. Storm patterns tend to be less pronounced and not as long lived. 24 NATURE of the Universe Astronomy - The Jovian Planets Basic Properties Atmospheric structure of Saturn and Jupiter is quite similar, though Saturn has a lower pressure. This results in thicker cloud layers, making it impossible to see deeper into Saturn's atmosphere. Saturn Jupiter 25 NATURE of the Universe Astronomy - The Jovian Planets Basic Properties Uranus has about 4 times the diameter of Earth, and about 15 times its mass. It looks quite featureless in the visible. Infrared observations reveal band structure, storm systems and rings. Note the strong tilt of the rotation axis! 26 The image on the left is a visible light image obtained by the Voyager 2 space probe. The image on the right is an infrared image obtained with the Keck telescope. NATURE of the Universe Astronomy - The Jovian Planets Basic Properties Because of the strong tilt of Uranus' rotation axis, seasons are extreme, and last a quarter of its rotation period around the Sun of 84 years. 27 NATURE of the Universe Astronomy - The Jovian Planets Basic Properties Neptune is similar in size and mass to Uranus, but shows clear banding and storms in the visual. More recently, Neptune started to develop extensive storm systems on its southern hemisphere, which is entering summer time. 28 NATURE of the Universe Astronomy - The Jovian Planets Inner structure The interior of Jupiter is not accessible. Its structure can be deduced from Jupiter's average density, the composition of its atmosphere, and the help of theoretical models. It is believed to be mostly hydrogen and helium, with a central rocky core of about 10 times the mass of Earth 29 NATURE of the Universe Astronomy - The Jovian Planets Inner structure Saturn's composition is similar to Jupiter, though its central rocky core seems to be more massive with about 15 times the mass of Earth. Because of their lower mass, both Uranus and Neptune cannot compress hydrogen and helium as much as Jupiter and Saturn. In order to explain the average densities of Uranus and Neptune, central rocky cores with about 10 times the mass of Earth are required. 30 NATURE of the Universe Astronomy - The Jovian Planets Summary Summary: The Jovian Planets Both Uranus and Neptune could only be discovered with a telescope. Deviations in Uranus' orbit led to the discovery of Neptune. Jupiter is the largest and most massive planet in the solar system. It has about 0.1% of the mass of the Sun, and 2.5 times more mass than all other planets combined. Jovian planets are gaseous, i.e. they do not have a solid surface. All develop weather systems with band structure and storm systems. 31 NATURE of the Universe Astronomy - The Jovian Planets Homework Homework Reading assignment: Chapter 8 No online Homework for Mo, Oct 30! Think about: What are the rings made of? How did the rings form? 32 NATURE of the Universe Astronomy - The Jovian Planets Mid-term Exam 1 - Stats Mid-term exam 1: dose of statistics Distribution of scores 41 - 45 correct answers 36 - 40 correct answers One perfect score (45 correct answers) Median: 40 correct answers Mean: 38.4 correct answers 32 - 35 correct answers 27 - 31 correct answers 23 - 26 correct answers 18 - 22 correct answers Answer key can be found on the class web page under "exams" You can view your individual score at my.ucla.edu See me during office hours in case you want to discuss specific questions and answers, or like, e.g., to review your scantron together with me. 33 Answer key to Mid-term exam 1 is available at http://web.physics.ucla.edu/class/06F/ 3_BRANDNER/exams/index.html ...
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This note was uploaded on 10/13/2008 for the course ASTR 3 taught by Professor Hauser during the Fall '07 term at UCLA.

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Lecture 12 - Jovian Planets - Saturn Uranus Neptune Jupiter...

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