Chapter 4The 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/m3)

Table 4-1Properties 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 4.2Planetary Alignment

Terrestrial planets

• Mercury

• Venus

• Earth

• Mars

Jovian planets

• Jupiter

• Saturn

• Uranus

• Neptune

• Memory aid: S-U-N

Figure 4.3 - Sun and Planets

Table 4-2

Comparison Between the Terrestrial and Jovian Planets

Table 4.2 - 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) Gasprab) 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 4-1aWhat Killed the Dinosaurs?

Discovery 4-1bWhat 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 4.9Comet 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

Stardustb) 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 4.14Meteor 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 AnalogyRailroad Tracks Converging

Meteor craters on earth

• About 100 craters over 100 m in diameter

• Others heavily eroded by weather or geological activity

Figure 4.17 - Barringer Crater, Arizona

Figure 4.18 Manicouagan

Reservoir, Quebec

Figure 4.19Tunguska Debris (Siberia, 1908)

Meteorite types

• Rocky silicate

• Iron with some nickel

• Carbonaceous

• 4.4 to 4.6 billion years old

Figure 4.20 - Meteorite Samples(a) rocky or stony (silicate) (b) iron and some nickel

Model of Solar System formation must explain1. 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 4-1The Concept of Angular Momentum

More Precisely 4-1bConservation of Angular Momentum

Figure 4.23 - 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