Chapter 15: The Formation of Planetary Systems The Birth of Our World - PowerPoint PPT Presentation

Loading...

PPT – Chapter 15: The Formation of Planetary Systems The Birth of Our World PowerPoint presentation | free to view - id: 86ec-ZWM1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Chapter 15: The Formation of Planetary Systems The Birth of Our World

Description:

The Solar System is highly differentiated ... More material in the outer solar system allowed four large protoplanets to form ... – PowerPoint PPT presentation

Number of Views:149
Avg rating:3.0/5.0
Slides: 23
Provided by: jbs
Category:

less

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

Title: Chapter 15: The Formation of Planetary Systems The Birth of Our World


1
Chapter 15 The Formation of Planetary
SystemsThe Birth of Our World
2
Modeling the Solar System
  • A complex problem only now becoming understood
  • Most of our knowledge of solar system formation
    comes from studies of
  • interstellar gas clouds
  • fallen meteorites
  • Earths Moon
  • Other planets and moon of the Solar System
  • Earth provides little clue, too much change
  • Extra solar planets are forcing a reevaluation of
    once held beliefs

3
Modeling the Solar System
  • Any model must prescribe to the know facts
  • For the Solar system these facts are
  • Each planet is relatively isolated in space
  • Planetary orbits are almost circular
  • Planetary orbits lie nearly in the same plane
  • The direction the Sun rotates and planets revolve
    are the same
  • The direction most planets revolve and the Sun
    rotates is the same

4
Modeling the Solar System
  • More Facts
  • Most moons rotate and revolve the same direction
    their planets rotate
  • The Solar System is highly differentiated
  • Asteroids are very old and share little in common
    with the planets or their moons
  • Comets are old, icy, and have very elliptical
    orbits

5
Nebular Theory
  • First proposed by Descartes, formalized by
    Laplace
  • The Sun and planets formed from a large cloud of
    interstellar gas
  • Conservation of angular momentum formed disk
  • The sun formed in the middle and the planets in
    the disk

6
Nebular Theory
  • Strengths
  • Explains planets circular orbit
  • Explains why planets orbit in a plane
  • Relates planet revolution with Suns rotation
  • Weaknesses
  • Laplaces ideal of planets formed from rings
    doesnt work
  • Interstellar dust is not accounted for

7
Condensation Theory
  • Keeps the ideal of solar nebula
  • Unlike nebular theory, planets formed in a way
    requiring the presence of interstellar dust
  • Dust acted as a catalyst for accretion

8
Condensation Theory
  • Solar nebula contracts to form a spinning disk
  • Interstellar dust grains act as condensation
    nuclei allowing accretion of planetesimals
  • Solar winds push gas out, outer planets already
    formed
  • Inner planets start to form from collisions of
    planetesimals
  • Collisions continue over time making the 4 inner
    planets

9
Accretion
  • Accretion- the slow build up of matter around
    dust grains
  • Create millions of small asteroid sized
    planetesimals
  • planetesimals collected through collisions
    forming protoplanets which continued to increase
    in size eventually forming the present planets

10
Outer Planet Formation
  • Two theories
  • More material in the outer solar system allowed
    four large protoplanets to form relatively
    quickly, which gravitationally attracted large
    amounts of the solar nebulas gas
  • Formed as miniature solar systems, condensing
    from instabilities in the initial solar nebula

11
Observational Evidence
  • Beta Pictoris has a visible disk of warm gas
    surrounding it
  • Star HR4796A evidence of planetessiamal growth

12
Temperature and Differentation
  • The solar nebula was hot in the middle(1000k)
    and cooler further out (100K near Saturn)
  • Far too hot in the inner solar system for
    anything but metals to exist
  • This is why the inner planets are so deficient in
    volatiles

13
Temperature and the Outer Planets
  • Temperature decreased with distance from the
    center of the solar nebula, allowing nonmetals to
    condense
  • This provided the Jovian planets with a great
    deal more material to accrete, hence their large
    size
  • Carbon, nitrogen, and oxygen were the first
    elements to condense

14
Jovian Planets, Comets and the 2 Clouds
  • The early outer solar system contained a great
    number of icy planetesimals
  • After the Jovian Planets formed, their gravity
    assisted these planetesimals to more distance
    orbits
  • This formed the Oort Cloud and left the Kuiper
    Belt just outside Neptunes Orbit

15
What happened to all the gas?
  • The inner planets were not massive enough to
    accrete the lightest gases of the Solar Nebula
  • Just prior to nuclear ignition, a star will enter
    the T Tauri phase, when the solar wind is very
    strong
  • This pressure pushed the gas out into space
    leaving the inner protoplanets and the already
    formed outer giants

16
Catastrophes
  • Condensation Theory explains most of the 9 points
    listed earlier
  • It explains some of the anomalies in the Solar
    System as well
  • Very large collisions can account for most of
    these aspects
  • Uranus tilt
  • Earth-Moon system

17
Planets Beyond the Solar System
  • It has long been thought that there are planetary
    systems besides the Solar System
  • It was not until the mid-Nineties that proof was
    provided
  • Direct observation not possible
  • Doppler wobbles

18
Indirect evidence Doppler Shifting
  • Extrasolar planets are too faint and close to
    their parent star for any current telescope to
    resolve
  • A strong indicator of a large planet orbiting a
    star is an observable wobble about their
    center of mass
  • Measurement of the Doppler shift of the light
    gives the planets mass

19
Examples
Velocity Curve Star HD130322b
20
Solar System Vs. Extrasolar Systems
21
Why are these systems so different from us?
  • To date only extrasolar planets of sizes
    comparable to Jupiter have been found
  • A terrestrial sized planets effect on a star is
    too small to be measured
  • Most extrasolar planets have very eccentric
    orbits
  • We are not seeing system edge on
  • Brown Dwarfs
  • Gravitation interactions kept the Jupiter in
    circular, cold orbit
  • We only have a small amount of data, and is not
    representative of ALL extrasolar planetary systems

22
Finding Earths
  • The rare event of a transit of an extrasolar
    planet and its star provides and alternate means
    of identification
  • An extrasolar planets spectra would provide
    clues about its atmosphere, and if it was
    Earthlike in nature

An Earth-like Spectra
About PowerShow.com