Chapters 7&8. ASTRONOMY 202 Spring 2007: Solar System Exploration. Class 21: Solar System [3/12/07] Announcements.

Transcription

1 ASTRONOMY 202 Spring 2007: Solar System Exploration Instructor: Dr. David Alexander Web-site: Class 21: Solar System [3/12/07] Announcements The Solar System Comparative Planetology Planetary Facts Planetary patterns Chapters 7&8 Now Playing: Dirt rocks and gas giants Terrestrial and Jovian planets Asteroids and Comets Quick tour of the solar system Exploring the planets

2 Announcements Web Project Window is open to choose web project window closes March 26 See class web-site for details and some news sites - science.nasa.gov is a good one for solar system Observing This week is lousy but we will try to get a night next week and I will also try to get the solar telescopes working

3 Test Results and Summary Avg. Score: 75 Median score: 73 σ = 20

4 NASA Podcasting Using an ipod or any portable MP3 player, you can explore the Universe while driving, jogging, waiting in line... just about anywhere. It's easy: tune in to the podcast. podcast at

5 The Solar System

6 Learning from Other Worlds 6 of the Solar System s 9 planets were known to the ancients: Mercury, Venus, Earth, Mars, Jupiter, Saturn Uranus was the first new planet discovered in 1781 by William and Caroline Herschel. Neptune was predicted by its gravitational influence on Uranus in Pluto was erroneously predicted and discovered in 1930 and was recently downsized to a dwarf planet. Comparative Planetology: learning about the planets by exploring them all. includes moons, asteroids and comets. Big success of Space Age science; in the last 35 years we have visited all the planets (but not Pluto), photographed asteroids close-up, passed by planetary moons (Io, Titan), sent a probe through the atmosphere of Titan, landed on our own Moon, collected samples of cometary material for return to Earth, sent probes through Jupiter s atmosphere and landed robotic rovers on Mars.

7 Planetary Information The relative sizes of the planets, their relative daily rotation and orbital periods, the inclination of their orbits, and their average temperatures all tell us something about how the solar system came into existence and what forces contributed to their development (both physical and chemical). Similar inclinations - typically Year longer than day - typically

8 Patterns in the Planets All planetary orbits are nearly circular and lie in nearly the same plane. All planets orbit the Sun in the same direction, counterclockwise as viewed from above. Most planets rotate in the same direction in which they orbit, with fairly small axis tilts. Most of the Solar System s large moons exhibit similar properties in their orbits around their planets.

9 Terrestrial and Jovian Planets Mercury Venus Earth Mars Pluto?? Jupiter Saturn Uranus Neptune Hydrogen compounds on gas giants include water (H 2 O), ammonia (NH 3 ), and methane (CH 4 )

10 Asteroids and Comets Eros Most asteroids reside in Asteroid Belt between Mars and Jupiter. Biggest is Ceres at ~900km. LINEAR Comets mostly ice(s) rather than rock like asteroids. Comets originate in Kuiper Belt ( AU) and Oort Cloud (30-60,000 AU). Comets have a plasma tail and a dust tail.

11 Asteroids and Comets Asteroids Made mostly of rock Orbit in inner solar system Orbit in same direction and nearly same plane as planets Kuiper Belt Comets Made mostly of ice Orbit between Neptune and about 100 AU from Sun Orbit in same direction and nearly same plane as planets Oort Cloud Comets Made mostly of ice Orbit at a great distance Orbits inclined at every possible angle and going in all possible directions

12 Summary of the Solar System PATTERNS OF MOTION TWO TYPES OF PLANETS ASTEROIDS AND COMETS EXCEPTIONS

13 Quick Tour Sun: >1000 more massive than everything else in the Solar System combined. Primarily influences planetary climates (regulating temperature). Mercury: 420 o C -150 o C Venus: ~450 o C - due to greenhouse effect of dense atmosphere. Earth: Only planet with abundant surface water to support life. Mars: Flowing water in past could imply existence of simple lifeforms. Jupiter: Has over 60 moons. If was times bigger would have become a star. Saturn: >30 moons. Much less dense than Jupiter. Moon Titan has an atmosphere (mostly Nitrogen). Uranus: Methane gives it a blue-green colour. Planet + rings tipped on its side. Planet George. Neptune: Twin of Uranus. Moon Triton seems to show geysers of Nitrogen gas and orbits planet backwards. Pluto: Large inclination to ecliptic plane and very eccentric orbit.