Transcript Lecture 1
http://www.theonion.com/content/node/32096
Lecture 21
Outline For Rest of Semester
• Oct. 29 th Chapter 9 (Earth) • Nov 3 rd and 5 th Chapter 9 and Chapter 10 (Earth and Moon) • Nov. 10 th and 12 th Mars, Venus, and Mercury • Nov. 17 th and 19 th Jupiter and Saturn • Nov 24 th Uranus and Neptune • Nov 26 th Thanksgiving • Dec. 1 st - Exam 3 • Dec. 3 rd – Pluto, and the Kuiper Belt • Dec. 8 th and 10 th – Chapter 7 and 8 (Comparative Planetology I and II) • Tuesday December 15 th (7:30 am – 10:15 am) Final Exam • No Reading days are scheduled this semester • Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on December 21
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
Questions
• On posting “(with answers)” notes • NASA finding water on the moon • Why so many questions?
• I have not had a chance to post Quiz solutions in ppt recently • #18 “made no sense”
#18 Mars’ Atmosphere
• Why does Earth have oxygen in its atmosphere while Mars does not?
Venus Greenhouse
• The so-called greenhouse effect, which produces very high temperatures on the surface of Venus, is … The absorption of CO 2 gas by the planet’s atmosphere of infrared radiation emitted by its surface.
Mercury Elongation
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
It is difficult to see!
http://homepage.ntlworld.com/mjpowell/Astro/Naked-Eye-Planets/Naked-Eye-Planets.htm
• Why is the ecliptic at an angle with respect to the horizon?
Typo?
• More than 1200 Earth’s would fit inside Jupiter • Jupiter is 11 times larger in diameter than Earth
Typo? No!
• More than 1200 Earth’s would fit inside Jupiter • Jupiter is 11 times larger in diameter than Earth V ~ R 3 ~ D 3 = (pi/6)D 3 V Earth ~ D 3 Earth V Jupiter ~ (11*D Earth ) 3 ~ (11) 3 D 3 Earth ~ 1300 D 3 Earth
Inferior planets superior planets
A planet’s synodic period is measured with respect to the Earth and the Sun (for example, from one opposition to the next)
• Rotation
al
• Orbit
al
• Sidere
al
• Synodic
Periods
Measured with respect to something that is not rotating or orbiting
Orbit
• http://learning.nd.edu/orbital/orbitals.swf
Extra-credit in-class Quiz Use cell phone if • If you have free text plan and • Don’t mind receiving ads otherwise Use notecard and hand in at end of class
Register for quiz 2
Text to 41411
:
astr111 2 rweigel
Replace with your GMU email name You will receive either one or two texts in response
Question
• Which is longer, Jupiter’s synodic or orbital period?
• Which is longer, Jupiter’s synodic or Saturn’s synodic period?
• Guess Jupiter’s and Saturn’s synodic period.
• Which is longer, Jupiter’s synodic or orbital period?
• Which is longer, Jupiter’s synodic or Saturn’s synodic period?
• Guess Jupiter’s and Saturn’s synodic period.
2 1 a Synodic, Jupiter’s, longer than Earth’s 2 1 b Synodic, Saturn’s, longer than Earth’s 2 1 c Synodic, Saturn’s, shorter than Earth’s 2 1 d Synodic,Jupiter’s, shorter than Earth’s 2 1 e Orbital, Jupiter’s, longer than Earth’s 2 1 f Orbital, Jupiter’s, longer than Earth’s 2 1 g Orbital, Saturn’s, longer than Earth’s 2 1 h Orbital, Saturn’s, longer than Earth’s
Question
Time to repeat from Earth’s perspective • Which is longer, Jupiter’s synodic or orbital period?
orbital
• Which is longer, Jupiter’s synodic or Saturn’s synodic period?
Jupiter’s
• Guess Jupiter’s and Saturn’s synodic period.
A little longer than Earth’s orbital period.
Kepler’s Third Law
P 2 = a 3
P
= planet’s sidereal period, in years
a
= planet’s semimajor axis, in AU
Long orbital periods of Jupiter and Saturn cause favorable viewing times to shift
What is wrong with either of these tables?
What is wrong with either of these tables?
Correct
The best time to observe Saturn from Earth is when it is 2 2 A. at opposition and it is midnight at your location on Earth. 2 2 B. at opposition and it is sunset or sunrise at your location on Earth. 2 2 C. at conjunction and it is midnight at your location on Earth. 2 2 D. at conjunction and it is sunset or sunrise at your location on Earth. 2 2 E. at opposition and it is just before sunrise at your location on Earth.
The best time to observe Saturn from Earth is when it is A. at opposition and it is midnight at your location on Earth. B. at opposition and it is sunset or sunrise at your location on Earth. C. at conjunction and it is midnight at your location on Earth. D. at conjunction and it is sunset or sunrise at your location on Earth. E. at opposition and it is just before sunrise at your location on Earth.
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
What happens to ornaments when hoop is spun?
hoop
2 3 A hoop 2 2 B 2 2 C 2 2 D
How to get Oblate
hoop
The farther away from the axis, the more “thrown out” it gets.
Extra-credit in-class Quiz Use cell phone if • If you have free text plan and • Don’t mind receiving ads otherwise Use notecard and hand in at end of class
All questions (correct or incorrect) worth 20 points (about two quiz questions).
Register for quiz
3 Text to 41411
:
astr111 3 rweigel
Replace with your GMU email name
NOT G NUMBER!
You will receive either one or two texts in response
Both have arms attached to ears and shoulders. When they spin, which pair of arms swings out the most? Least?
W X 3 1 3 1 a. X Most, Y Least b. Y Least, X Most 3 1 3 1 c. W Most, Y Least d. X,Y,Z Most, W Least 3 1 e. W Most, X, Y, Z Least W Y X Z Y Z
Both have arms attached to ears and shoulders. When they spin, which pair of arms swings out the most? Least?
W X 3 1 3 1 a. X Most, Y Least b. Y Least, X Most 3 1 3 1 c. W Most, Y Least d. X,Y,Z Most, W Least 3 1 e. W Most, X, Y, Z Least W Y X Z Y Z
The farther away from the axis, the more “thrown out” it gets.
Both have arms attached to ears and shoulders. When they spin, which pair of arms swings out the most? Least?
All red arms are same distance from spin axis.
Black arms are closer.
Red arms swing out most.
Black arms wing out least.
The oblateness of Jupiter and Saturn reveals their rocky cores
• Jupiter probably has a rocky core several times more massive than the Earth • The core is surrounded by a layer of liquid “ices” (water, ammonia, methane, and associated compounds)
The oblateness of Jupiter and Saturn reveals their rocky cores
• On top of this is a layer of helium and
liquid metallic hydrogen
and an outermost layer composed primarily of ordinary hydrogen and helium • Saturn’s internal structure is similar to that of Jupiter, but its core makes up a larger fraction of its volume and its liquid metallic hydrogen mantle is shallower than that of Jupiter
Metallic hydrogen inside Jupiter and Saturn endows the planets with strong magnetic fields • Jupiter and Saturn have strong magnetic fields created by currents in the metallic hydrogen layer • Jupiter’s huge magnetosphere contains a vast current sheet of electrically charged particles • Saturn’s magnetic field and magnetosphere are much less extensive than Jupiter’s
Jupiter and Saturn have extensive magnetospheres • The Jovian magnetosphere encloses a low-density plasma of charged particles • The magnetosphere exists in a delicate balance between pressures from the plasma and from the solar wind • When this balance is disturbed, the size of the magnetosphere fluctuates drastically
Synchrotron Radiation
Charged particles in the densest portions of Jupiter’s magnetosphere emit synchrotron radiation at radio wavelengths
Golf!
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
Atmospheres
• gravity and escape velocity
Atmospheres
• gravity and escape velocity
Atmospheres
• The visible “surfaces” of Jupiter and Saturn are actually the tops of their clouds
Atmospheres
• The rapid rotation of the planets twists the clouds into dark belts and light zones that run parallel to the equator
The chemical composition of Jupiter and Saturn is difficult to measure. Why?
Atmospheres
• The outer layers of both planets’ atmospheres show differential rotation – The equatorial regions rotate slightly faster than the polar regions
Atmospheres
• For both Jupiter and Saturn, the polar rotation rate is nearly the same as the internal rotation rate
Spacecraft images show remarkable activity in the clouds of Jupiter and Saturn
Video
• Chapter 14 videos • http://bcs.whfreeman.com/universe7e
Storms
• Both Jupiter and Saturn emit more energy than they receive from the Sun • Presumably both planets are still cooling • The colored ovals visible in the Jovian atmosphere represent gigantic storms • Some, such as the Great Red Spot, are quite stable and persist for many years
Storms in Saturn’s atmosphere seem to be shorter-lived
The internal heat of Jupiter and Saturn has a major effect on the planets’ atmospheres
• Explain how Infrared and Visible (indicated on the previous slide) relate to the blackbody curves we studied.
• X-Ray image at airport http://static.howstuffworks.com/gif/airport-security-xray2.jpg
A space probe has explored Jupiter’s deep atmosphere
• There are presumed to be three cloud layers in the atmospheres of Jupiter and Saturn • The reasons for the distinctive colors of these different layers are not yet known • The cloud layers in Saturn’s atmosphere are spread out over a greater range of altitude than those of Jupiter, giving Saturn a more washed-out appearance
Spacecraft images show remarkable activity in the clouds of Jupiter and Saturn
In the news: Hurricane on Saturn?
• • http://saturn.jpl.nasa.gov/multimedia/videos/video-details.cfm?videoID=136 http://www.youtube.com/watch?v=dnF6PV SSSag – Hurricane-like vortex at Saturn's south pole, where the vertical structure of the clouds is highlighted by shadows. Such a storm, with a well-developed eye ringed by towering clouds, is a phenomenon never before seen on another planet.
Both Jupiter and Saturn emit more energy than they receive from the Sun. What does this tell us?
Jupiter radiates more energy into space than it receives from the Sun. What is the primary source of the excess energy that Jupiter radiates?
3 2 A. Decay of radioactive materials in Jupiter's core 3 2 3 2 B. Tidal forces from Jupiter's moons C. Jupiter is still contracting, and the contraction releases energy 3 2 D. Jupiter's rotation is slowing down dramatically, and this slowdown releases energy 3 2 E. All of the above are the energy sources
Jupiter radiates more energy into space than it receives from the Sun. What is the primary source of the excess energy that Jupiter radiates?
3 2 A. Decay of radioactive materials in Jupiter's core 3 2 3 2 B. Tidal forces from Jupiter's moons C. Jupiter is still contracting, and the contraction releases energy 3 2 D. Jupiter's rotation is slowing down dramatically, and this slowdown releases energy 3 2 E. All of the above are the energy sources
What can you say about these planets?
• 3 3 a 3 3 b 3 3 c 3 3 d If both these planets formed at the same time, which would be expected to be warmer?
Which would be expected to have more tectonic activity?
Planet #1 , Planet #1 Planet #1 , Planet #2 Planet #2 , Planet #2 Planet #2 , Planet #1
• 3 3 a 3 3 b 3 3 c 3 3 d If both these planets formed at the same time, which would be expected to be warmer?
Which would be expected to have more tectonic activity?
Planet #1 , Planet #1 Planet #1 , Planet #2 Planet #2 , Planet #2 Planet #2 , Planet #1
If Jupiter and Saturn formed at the same time, which should be emitting more heat?
• Saturn’s atmosphere contains less helium than Jupiter’s atmosphere • This lower abundance may be the result of helium raining downward into the planet • Helium “rainfall” may also account for Saturn’s surprisingly strong heat output
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
• Link
Something is Fishy
• How can a planet be solid?
• Pebbles, snowballs and boulder size • How was this determined?
• Videos 12.8-12.10
Earth-based observations reveal three broad rings encircling Saturn
• Saturn is circled by a system of thin, broad rings lying in the plane of the planet’s equator • This system is tilted away from the plane of Saturn’s orbit, which causes the rings to be seen at various angles by an Earth-based observer over the course of a Saturnian year
Saturn’s rings are composed of numerous icy fragments, while Jupiter’s rings are made of small rocky particles • The principal rings of Saturn are composed of numerous particles of ice and ice-coated rock ranging in size from a few micrometers to about 10 m • Jupiter’s faint rings are composed of a relatively small amount of small, dark, rocky particles that reflect very little light
• Most of its rings exist inside the Roche limit of Saturn, where disruptive tidal forces are stronger than the gravitational forces attracting the ring particles to each other • Each of Saturn’s major rings is composed of a great many narrow ringlets
Saturn’s rings consist of thousands of narrow, closely spaced ringlets
Saturn’s inner satellites affect the appearance and structure of its rings
The faint F ring, which is just outside the A ring, is kept narrow by the gravitational pull of shepherd satellites
Outline
• Jupiter and Saturn – Orbit – Surface – Atmosphere – Rings – Moons
Preview
• Already discussed influence on Saturn’s rings.
• Jupiter’s moons are even more interesting