Chapter 6 Formation of Planetary Systems Our Solar System and Beyond - PowerPoint PPT Presentation

Loading...

PPT – Chapter 6 Formation of Planetary Systems Our Solar System and Beyond PowerPoint presentation | free to view - id: 84465f-NDc5Y



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Chapter 6 Formation of Planetary Systems Our Solar System and Beyond

Description:

Chapter 6 Formation of Planetary Systems Our Solar System and Beyond 6.1 A Brief Tour of the Solar System Our goals for learning: What does the solar system look like? – PowerPoint PPT presentation

Number of Views:179
Avg rating:3.0/5.0
Slides: 106
Provided by: MarkV203
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Chapter 6 Formation of Planetary Systems Our Solar System and Beyond


1
Chapter 6 Formation of Planetary Systems Our
Solar System and Beyond
2
6.1 A Brief Tour of the Solar System
  • Our goals for learning
  • What does the solar system look like?

3
The solar system exhibits clear patterns of
composition and motion. These patterns are far
more important and interesting than numbers,
names, and other trivia.
4
Planets are very tiny compared to distances
between them.
5
Sun
  • Over 99.9 of solar systems mass
  • Made mostly of H/He gas (plasma)
  • Converts 4 million tons of mass into energy each
    second

6
Mercury
  • Made of metal and rock large iron core
  • Desolate, cratered long, tall, steep cliffs
  • Very hot and very cold 425C (day), 170C
    (night)

7
Venus
  • Nearly identical in size to Earth surface
    hidden by clouds
  • Hellish conditions due to an extreme greenhouse
    effect
  • Even hotter than Mercury 470C, day and night

8
Earth
Earth and Moon to scale
  • An oasis of life
  • The only surface liquid water in the solar
    system
  • A surprisingly large moon

9
Mars
  • Looks almost Earth-like, but dont go without a
    spacesuit!
  • Giant volcanoes, a huge canyon, polar caps, and
    more
  • Water flowed in the distant past could there
    have been life?

10
Jupiter
  • Much farther from Sun than inner planets
  • Mostly H/He no solid surface
  • 300 times more massive than Earth
  • Many moons, rings

11
Jupiters moons can be as interesting as planets
themselves, especially Jupiters four Galilean
moons
  • Io (shown here) Active volcanoes all over
  • Europa Possible subsurface ocean
  • Ganymede Largest moon in solar system
  • Callisto A large, cratered ice ball

12
Saturn
  • Giant and gaseous like Jupiter
  • Spectacular rings
  • Many moons, including cloudy Titan
  • Cassini spacecraft currently studying it

13
Rings are NOT solid they are made of countless
small chunks of ice and rock, each orbiting like
a tiny moon.
Artists conception
The Rings of Saturn
14
Cassini probe arrived July 2004. (Launched in
1997)
15
Uranus
  • Smaller than Jupiter/Saturn much larger than
    Earth
  • Made of H/He gas and hydrogen compounds (H2O,
    NH3, CH4)
  • Extreme axis tilt
  • Moons and rings

16
Neptune
  • Similar to Uranus (except for axis tilt)
  • Many moons (including Triton)

17
Pluto and Eris
  • Much smaller than other planets
  • Icy, comet-like composition
  • Plutos moon Charon is similar in size to Pluto

18
What have we learned?
  • What does the solar system look like?
  • Planets are tiny compared to the distances
    between them.
  • Each world has its own character, but there are
    many clear patterns.

19
6.2 Clues to the Formation of Our Solar System
  • Our goals for learning
  • What features of our solar system provide clues
    to how it formed?
  • What theory best explains the features of our
    solar system?

20
What features of our solar system provide clues
to how it formed?
21
Motion of Large Bodies
  • All large bodies in the solar system orbit in the
    same direction and in nearly the same plane.
  • Most also rotate in that direction.

22
Two Major Planet Types
  • Terrestrial planets are rocky, relatively small,
    and close to the Sun.
  • Jovian planets are gaseous, larger, and farther
    from the Sun.

23
Swarms of Smaller Bodies
  • Many rocky asteroids and icy comets populate the
    solar system.

24
Notable Exceptions
  • Several exceptions to normal patterns need to be
    explained.

25
What theory best explains the features of our
solar system?
26
According to the nebular theory, our solar system
formed from a giant cloud of interstellar gas.
(nebula cloud)
27
What have we learned?
  • What features of our solar system provide clues
    to how it formed?
  • Motions of large bodies All in same direction
    and plane
  • Two major planet types Terrestrial and jovian
  • Swarms of small bodies Asteroids and comets
  • Notable exceptions Rotation of Uranus, Earths
    large moon, and so forth

28
What have we learned?
  • What theory best explains the features of our
    solar system?
  • The nebular theory, which holds that our solar
    system formed from a cloud of interstellar gas,
    explains the general features of our solar system.

29
6.3 The Birth of the Solar System
  • Our goals for learning
  • Where did the solar system come from?
  • What caused the orderly patterns of motion in our
    solar system?

30
Where did the solar system come from?
31
Galactic Recycling
  • Elements that formed planets were made in stars
    and then recycled through interstellar space.

32
Evidence from Other Gas Clouds
  • We can see stars forming in other interstellar
    gas clouds, lending support to the nebular theory.

The Orion Nebula with Proplyds
33
What caused the orderly patterns of motion in our
solar system?
34
Orbital and Rotational Properties of the Planets
35
Conservation of Angular Momentum
  • The rotation speed of the cloud from which our
    solar system formed must have increased as the
    cloud contracted.

36
Rotation of a contracting cloud speeds up for the
same reason a skater speeds up as she pulls in
her arms.
Collapse of the Solar Nebula
37
Flattening
  • Collisions between particles in the cloud caused
    it to flatten into a disk.

38
Collisions between gas particles in a cloud
gradually reduce random motions.
Formation of Circular Orbits
39
Collisions between gas particles also reduce up
and down motions.
Why does the Disk Flatten?
40
The spinning cloud flattens as it shrinks.
Formation of the Protoplanetary Disk
41
Disks Around Other Stars
  • Observations of disks around other stars support
    the nebular hypothesis.

42
What have we learned?
  • Where did the solar system come from?
  • Galactic recycling built the elements from which
    planets formed.
  • We can observe stars forming in other gas
    clouds.
  • What caused the orderly patterns of motion in our
    solar system?
  • The solar nebula spun faster as it contracted
    because of conservation of angular momentum.
  • Collisions between gas particles then caused the
    nebula to flatten into a disk.
  • We have observed such disks around newly forming
    stars.

43
6.4 The Formation of Planets
  • Our goals for learning
  • Why are there two major types of planets?
  • Where did asteroids and planets come from?
  • Do we explain the existence of the Moon and other
    exceptions to the rules?
  • When did the planets form?

44
Why are there two major types of planets?
45
Conservation of Energy
As gravity causes the cloud to contract, it heats
up.
Collapse of the Solar Nebula
46
Inner parts of the disk are hotter than outer
parts. Rock can be solid at much higher
temperatures than ice.
Temperature Distribution of the Disk and the
Frost Line
47
Fig 9.5
Inside the frost line Too hot for hydrogen
compounds to form ices Outside the frost line
Cold enough for ices to form
48
Formation of Terrestrial Planets
  • Small particles of rock and metal were present
    inside the frost line.
  • Planetesimals of rock and metal built up as these
    particles collided.
  • Gravity eventually assembled these planetesimals
    into terrestrial planets.

49
Tiny solid particles stick to form planetesimals.
Summary of the Condensates in the Protoplanetary
Disk
50
Gravity draws planetesimals together to form
planets. This process of assembly is called
accretion.
Summary of the Condensates in the Protoplanetary
Disk
51
Accretion of Planetesimals
  • Many smaller objects collected into just a few
    large ones.

52
Formation of Jovian Planets
  • Ice could also form small particles outside the
    frost line.
  • Larger planetesimals and planets were able to
    form.
  • The gravity of these larger planets was able to
    draw in surrounding H and He gases.

53
The gravity of rock and ice in jovian planets
draws in H and He gases.
Nebular Capture and the Formation of the Jovian
Planets
54
Moons of jovian planets form in miniature disks.
55
Radiation and outflowing matter from the Sun
the solar wind blew away the leftover gases.
The Solar Wind
56
Where did asteroids and comets come from?
57
Asteroids and Comets
  • Leftovers from the accretion process
  • Rocky asteroids inside frost line
  • Icy comets outside frost line

58
Heavy Bombardment
  • Leftover planetesimals bombarded other objects in
    the late stages of solar system formation.

59
Origin of Earths Water
  • Water may have come to Earth by way of icy
    planetesimals from the outer solar system.

60
How do we explain the existence of our Moon and
other exceptions to the rules?
61
Captured Moons
  • The unusual moons of some planets may be captured
    planetesimals.

62
Giant Impact
Giant impact stripped matter from Earths crust
Stripped matter began to orbit
Then accreted into Moon
63
Odd Rotation
  • Giant impacts might also explain the different
    rotation axes of some planets.

64
Review of nebular theory
65
Thought Question
  • How would the solar system be different if the
    solar nebula had cooled with a temperature half
    its current value?
  • Jovian planets would have formed closer to the
    Sun.
  • There would be no asteroids.
  • There would be no comets.
  • Terrestrial planets would be larger.

66
Thought Question
  • How would the solar system be different if the
    solar nebula had cooled with a temperature half
    its current value?
  • Jovian planets would have formed closer to the
    Sun.
  • There would be no asteroids.
  • There would be no comets.
  • Terrestrial planets would be larger.

67
Thought Question
  • Which of these facts is NOT explained by the
    nebular theory?
  • There are two main types of planets terrestrial
    and jovian.
  • Planets orbit in the same direction and plane.
  • Asteroids and comets exist.
  • There are four terrestrial and four jovian
    planets.

68
Thought Question
  • Which of these facts is NOT explained by the
    nebular theory?
  • There are two main types of planets terrestrial
    and jovian.
  • Planets orbit in the same direction and plane.
  • Asteroids and comets exist.
  • There are four terrestrial and four jovian
    planets.

69
When did the planets form?
  • We cannot find the age of a planet, but we can
    find the ages of the rocks that make it up.
  • We can determine the age of a rock through
    careful analysis of the proportions of various
    atoms and isotopes within it.

70
Radioactive Decay
  • Some isotopes decay into other nuclei.
  • A half-life is the time for half the nuclei in a
    substance to decay.

71
Thought Question
  • Suppose you find a rock originally made of
    potassium-40, half of which decays into argon-40
    every 1.25 billion years. You open the rock and
    find 15 atoms of argon-40 for every atom of
    potassium-40. How long ago did the rock form?
  • 1.25 billion years ago
  • 2.5 billion years ago
  • 3.75 billion years ago
  • 5 billion years ago

72
Thought Question
  • Suppose you find a rock originally made of
    potassium-40, half of which decays into argon-40
    every 1.25 billion years. You open the rock and
    find 15 atoms of argon-40 for every atom of
    potassium-40. How long ago did the rock form?
  • 1.25 billion years ago
  • 2.5 billion years ago
  • 3.75 billion years ago
  • 5 billion years ago

73
Dating the Solar System
  • Age dating of meteorites that are unchanged since
    they condensed and accreted tells us that the
    solar system is about 4.6 billion years old.

74
Dating the Solar System
  • Radiometric dating tells us that the oldest moon
    rocks are 4.4 billion years old.
  • The oldest meteorites are 4.55 billion years old.
  • Planets probably formed 4.5 billion years ago.

75
What have we learned?
  • Why are there two major types of planets?
  • Rock, metals, and ices condensed outside the
    frost line, but only rock and metals condensed
    inside the frost line.
  • Small solid particles collected into
    planetesimals that then accreted into planets.
  • Planets inside the frost line were made of rock
    and metals.
  • Additional ice particles outside the frost line
    made planets there more massive, and the gravity
    of these massive planets drew in H and He gases.

76
What have we learned?
  • Where did asteroids and comets come from?
  • They are leftover planetesimals, according to the
    nebular theory.
  • How do we explain the existence of Earths moon
    and other exceptions to the rules?
  • The bombardment of newly formed planets by
    planetesimals may explain the exceptions.
  • Material torn from Earths crust by a giant
    impact formed the Moon.
  • When did the planets form?
  • Radiometric dating indicates that planets formed
    4.5 billion years ago.

77
6.5 Other Planetary Systems
  • Our goals for learning
  • How do we detect planets around other stars?
  • How do extrasolar planets compare with those in
    our own solar system?
  • Do we need to modify our theory of solar system
    formation?

78
How do we detect planets around other stars?
79
Planet Detection
  • Direct Pictures or spectra of the planets
    themselves
  • Indirect Measurements of stellar properties
    revealing the effects of orbiting planets

80
Gravitational Tugs
  • The Sun and Jupiter orbit around their common
    center of mass.
  • The Sun therefore wobbles around that center of
    mass with the same period as Jupiter.

Stellar Motion due to Planetary Orbits
81
Gravitational Tugs
  • Suns motion around solar systems center of mass
    depends on tugs from all the planets.
  • Astronomers who measured this motion around other
    stars could determine masses and orbits of all
    the planets.

82
Astrometric Technique
  • We can detect planets by measuring the change in
    a stars position in the sky.
  • However, these tiny motions are very difficult to
    measure (0.001 arcsecond).

83
Doppler Technique
  • Measuring a stars Doppler shift can tell us its
    motion toward and away from us.
  • Current techniques can measure motions as small
    as 1 m/s (walking speed!).

Oscillation of a Star's Absorption Line
84
First Extrasolar Planet Detected
  • Doppler shifts of star 51 Pegasi indirectly
    reveal planet with 4-day orbital period
  • Short period means small orbital distance
  • First extrasolar planet to be discovered (1995)

85
First Extrasolar Planet Detected
  • The planet around 51 Pegasi has a mass similar to
    Jupiters, despite its small orbital distance.

86
Thought Question
Suppose you found a star with the same mass as
the Sun moving back and forth with a period of 16
months. What could you conclude?
  1. It has a planet orbiting at less than 1 AU.
  2. It has a planet orbiting at greater than 1 AU.
  3. It has a planet orbiting at exactly 1 AU.
  4. It has a planet, but we do not have enough
    information to know its orbital distance.

87
Thought Question
Suppose you found a star with the same mass as
the Sun moving back and forth with a period of 16
months. What could you conclude?
  • It has a planet orbiting at less than 1 AU.
  • It has a planet orbiting at greater than 1 AU.
  • It has a planet orbiting at exactly 1 AU.
  • It has a planet, but we do not have enough
    information to know its orbital distance.

88
Transits and Eclipses
  • A transit is when a planet crosses in front of a
    star.
  • The resulting eclipse reduces the stars apparent
    brightness and tells us the planets radius.
  • When there is no orbital tilt, an accurate
    measurement of planet mass can be obtained.

Planetary Transits
89
Direct Detection
  • Special techniques for concentrating or
    eliminating bright starlight are enabling the
    direct detection of planets.

90
How do extrasolar planets compare with those in
our solar system?
91
Measurable Properties
  • Orbital period, distance, and shape
  • Planet mass, size, and density
  • Composition

92
Orbits of Extrasolar Planets
  • Most of the detected planets have orbits smaller
    than Jupiters.
  • Planets at greater distances are harder to detect
    with the Doppler technique.

93
Orbits of Extrasolar Planets
  • Most of the detected planets have greater mass
    than Jupiter.
  • Planets with smaller masses are harder to detect
    with the Doppler technique.

94
Planets Common or Rare?
  • One in ten stars examined so far have turned out
    to have planets.
  • The others may still have smaller (Earth-sized)
    planets that cannot be detected using current
    techniques.

95
Surprising Characteristics
  • Some extrasolar planets have highly elliptical
    orbits.
  • Some massive planets orbit very close to their
    stars Hot Jupiters.

96
Hot Jupiters
97
Do we need to modify our theory of solar system
formation?
98
Revisiting the Nebular Theory
  • Nebular theory predicts that massive Jupiter-like
    planets should not form inside the frost line (at
    ltlt 5 AU).
  • The discovery of hot Jupiters has forced a
    reexamination of nebular theory.
  • Planetary migration or gravitational encounters
    may explain hot Jupiters.

99
Planetary Migration
  • A young planets motion can create waves in a
    planet-forming disk.
  • Models show that matter in these waves can tug on
    a planet, causing its orbit to migrate inward.

100
Gravitational Encounters
  • Close gravitational encounters between two
    massive planets can eject one planet while
    flinging the other into a highly elliptical
    orbit.
  • Multiple close encounters with smaller
    planetesimals can also cause inward migration.

101
Thought Question
  • What happens in a gravitational encounter that
    allows a planets orbit to move inward?
  • It transfers energy and angular momentum to
    another object.
  • The gravity of the other object forces the planet
    to move inward.
  • It gains mass from the other object, causing its
    gravitational pull to become stronger.

102
Thought Question
  • What happens in a gravitational encounter that
    allows a planets orbit to move inward?
  • It transfers energy and angular momentum to
    another object.
  • The gravity of the other object forces the planet
    to move inward.
  • It gains mass from the other object, causing its
    gravitational pull to become stronger.

103
Modifying the Nebular Theory
  • Observations of extrasolar planets have shown
    that the nebular theory was incomplete.
  • Effects like planet migration and gravitational
    encounters might be more important than
    previously thought.

104
What have we learned?
  • How do we detect planets around other stars?
  • A stars periodic motion (detected through
    Doppler shifts) tells us about its planets.
  • Transiting planets periodically reduce a stars
    brightness.
  • Direct detection is possible if we can block the
    stars bright light.

105
What have we learned?
  • How do extrasolar planets compare with those in
    our solar system?
  • Detected planets are all much more massive than
    Earth.
  • Most have orbital distances smaller than
    Jupiters, and have highly elliptical orbits.
  • Hot Jupiters have been found.
  • Do we need to modify our theory of solar system
    formation?
  • Migration and encounters may play a larger role
    than previously thought.
About PowerShow.com