Chapter 4 The Solar System
Comet Tempel
Chapter overview Solar system inhabitants Solar system formation Extrasolar planets
Solar system inhabitants Sun Planets Moons Asteroids Comets Meteoroids Kuiper Belt Objects
Figure 4.1 Solar System
Planets Orbital size Orbital period Mass Radius Moons Density (water density is 1000 kg/m 3 )
Table 4-1 Properties of Some Solar System Objects
Planetary orbits Lie in same plane (ecliptic plane) Mercury and Pluto are slight exceptions Orbit around sun in same direction
Figure 4.2 Planetary Alignment
Terrestrial planets Mercury Venus Earth Mars
Jovian planets Jupiter Saturn Uranus Neptune Memory aid: S-U-N
Figure Sun and Planets
Table 4-2 Comparison Between the Terrestrial and Jovian Planets Table Comparison Between the Terrestrial and Jovian Planets
Other planet? Pluto As of late 2006, demoted from a planet
Interplanetary matter Asteroids Comets Meteoroids
Figure 4.4 Inner Solar System
Asteroids Asteroid belt Between orbits of Mars and Jupiter Noticeably elliptical orbits Trojan asteroids Earth crossing asteroids Up to 1000 km in size
Figure 4.5 Asteroids, from Earth
Figure 4.6 Asteroids, Close-up a) Gaspra b) Ida with Dactyl c) Mathilde
Asteroid types Carbonaceous Dark, water ice and organics (carbon) Silicate Reflective, more rocky Inner portion of asteroid belt
Figure 4.7 Asteroid Eros
Discovery 4-1a What Killed the Dinosaurs?
Discovery 4-1b What Killed the Dinosaurs?
Figure 4.8 Halley’s Comet
Comets Nucleus Coma (dust and evaporated gas) Hydrogen envelope Ion tail Dust tail Tails directed away from sun
Figure 4.9 Comet Tails - Comet Hale-Bopp 1997
Figure 4.10 Comet Trajectory
Figure 4.11 Halley’s Comet Close-up from Giotto spacecraft in 1986
Figure 4.12 a) Comet Wild-2 from Spacecraft Stardust b) aerogel for comet dust
Short period comet orbits Short period (< 200 years) Kuiper belt (beyond Neptune) 30 to 100 AU from sun Roughly circular orbits, in ecliptic plane Occasionally kicked into inner solar system About 900 Kuiper belt objects (KBO) known Some KBO’s larger than Pluto
Long period comet orbits Long period (> 200 years) Oort cloud Up to 100,000 AU diameter Random orbital orientation Occasionally kicked into inner solar system
Figure 4.13 Comet Reservoirs
Meteor terminology Meteoroid (chunk of space debris) Meteor (streak of light in sky) Meteorite (piece of meteoroid that falls to ground) Micrometeoroids Meteoroid swarm or shower (cometary debris)
Figure 4.14 Meteor Trails
Figure 4.15 Meteor Showers
Table 4-3 Some Prominent Meteor Showers Table 4.3 Some Prominent Meteor Showers
Figure 4.16 Radiant
Figure 4.16 Analogy Railroad Tracks Converging
Meteor craters on earth About 100 craters over 100 m in diameter Others heavily eroded by weather or geological activity
Figure Barringer Crater, Arizona
Figure 4.18 Manicouagan Reservoir, Quebec
Figure 4.19 Tunguska Debris (Siberia, 1908)
Meteorite types Rocky silicate Iron with some nickel Carbonaceous 4.4 to 4.6 billion years old
Figure Meteorite Samples (a) rocky or stony (silicate) (b) iron and some nickel
Model of Solar System formation must explain 1.Each planet isolated 2.Planet orbits nearly circular 3.Planet orbits nearly lie in a plane 4.Planets orbit sun in same direction sun rotates 5.Most planets rotate in same direction sun rotates 6.Most moons revolve in direction planet rotates 7.Terrestrial vs. Jovian planets 8.Asteroids are old and are unlike planets 9.Kuiper belt objects 10.Oort cloud comets
Figure 4.21 Angular Momentum
Figure 4.22 Beta Pictoris
More Precisely 4-1 The Concept of Angular Momentum
More Precisely 4-1b Conservation of Angular Momentum
Figure Dark Cloud containing interstellar dust and gas
Formation of solar system Nebular contraction Spinning material flattens into pancake as it contracts Condensation of interstellar dust Accretion Millions of planetesimals Protoplanets Fragmentation Protosun
Figure 4.24 Solar System Formation
Figure 4.25 Newborn Solar Systems?
Jovian planets Outer planets grew rapidly Gravitationally attracted gas from solar nebula Or could have started as gravitational instabilities in solar nebula
Figure 4.26 Jovian Condensation
Figure 4.27 Temperature in the Early Solar Nebula
Figure 4.28 Planetesimal Ejection
Figure 4.29 Extrasolar Planet
Extrasolar planets Indirectly detected by motion of star Large Jupiter-like planets in small orbits Selection effect Only detect largest and closest to the star Is our solar system unique?
Figure 4.30 Planets Revealed
Figure 4.31 An Extrasolar Transit
Figure 4.32 Extrasolar Orbits
Figure 4.33 Sinking Planet