Condensation of the Solar Nebula

1
Condensation of the Solar Nebula

• Composition of the Solar Nebula
• As the protoplanetary disk cools, materials in
  the disk condensate into planetesimals
• The solar nebular contains 98 Hydrogen and
  Helium (produced in the Big Bang), and 2
  everything else (heavy elements, fusion products
  inside the stars).
• Local thermal environment (Temperature)
  determines what kind of material condensates.
• Water and most hydrogen compounds have low
  sublimation temperature, and cannot exist near
  the Sun. They exist far away from the Sun.
• Metals and rocks have high sublimation
  temperature, and can form near the Sun.
• Frost line lies between the orbit of Mars and
  Jupiter.

2
The Four Phases of Matter

• There are in fact more than three phases of
  matter.
• Plasma when the temperature is very high, high
  energy collision between atoms will knock the
  electrons lose, and they are not bounded to the
  atoms anymore

Whats wrong with this picture?
Core and corona of the Sun and stars
Red is cold, Blue is hot!
Surface of the Sun and stars
Surface of Earth
White dwarfs, CMB
3
Transition Between Phases
Liquidation
Evaporation
Solid
Liquid
Gas
Solidification
Condensation
Condensation
Sublimation atoms or molecules escape into the
gas phase from a solid.
4
Accretion Formation of the Terrestrial Planets

• Accretion The process by which small seeds grew
  into planets.
• Near the Sun, where temperature is high, only
  metals and rocks can condense. The small pieces
  of metals and rocks (the planetesimals) collide
  and stick together to form larger piece of
  planetesimals.
• Small pieces of planetesimals can have any kind
  of shape.
• Larger pieces of planetesimals are spherical due
  to gravity.
• Only small planets can be formed due to limited
  supply of material (0.6 of the total materials
  in the solar nebula).
• Gravity of the small terrestrial planets is too
  weak to capture large amount of gas.
• The gas near the Sun were blown away by solar
  wind.

Click it!
5
Solar Winds

• Solar wind is the constant outflow of gas from
  the Sun
• Evidences of Solar Wind
• Tails of Comet always point away from the Sun,
  indicative of the existence of solar wind.
• SOHO (SOlar and Heliospheric Observatory) C2 and
  C3 movies.
• Effects of Solar Wind on Planet Formation
• At certain stage of the planet forming process,
  Solar winds blow away the gases in the planetary
  nebula, ending the formation of the planets.

6
Nebula Capture Formation of the Jovian Planets

• In the regions beyond the frost line, there are
  abundant supply of solid materials (ice), which
  quickly grow in size by accretion.
• The large planetesimals attract materials around
  them gravitationally, forming the jovian planets
  in a process similar to the gravitational
  collapse of the solar nebula (heating, spinning,
  flattening) to form a small accretion disk.
• Abundant supply of gases allows for the creation
  of large planets.
• However, the jovian planets were not massive
  enough to trigger nuclear fusion at their core.

7
The Results of Selective Condensation

• Not much light gases were available for the
  formation of planets near the Sun, but small
  amount of metals and rocks are available
• The planets close to the Sun are small and rocky
• There are abundant supply of light gases farther
  out
• The planets far away from the Sun are big and
  composed of gases of hydrogen components
• These processes can explain the two types of
  major planets, their size differences, locations,
  and composition.

8
Origin of Comets and Asteroids

• Asteroids
• Rocky leftover planetesimals of the inner solar
  system.
• Most of the asteroids are concentrated in the
  asteroid belt between the orbit of Mars and
  Jupiter.
• Jupiters strong gravity might have disturbed the
  formation of a terrestrial planet here.
• Jupiter also affects the orbit of these asteroids
  and sent them flying out of the solar system, or
  sent them into a collision cause with other
  planets.
• Comets
• Icy leftover planetesimals of the outer solar
  system.
• Comets in between Jupiter and Neptune were
  bullied away from this region, either collide
  with the big planets, or been sent out to the
  Kuiper belt or the Oort cloud.
• Comets beyond the orbit of Neptune have time to
  grow larger, and stay in stable orbit. Pluto may
  be (the biggest) one of them.

9
Explaining the Exceptions Impact and Capture
Heavy Bombardment There were many impact events
during the early stage of the solar system
formation process, when there were still many
planetesimals floating around.

• Evidences of Impact
• Comet Shoemakers collision with Jupiter
• Surface of the Moon and Mercury,
• More in Chapter 7

• Effects of Impact
• Tilt of the rotation axis of planets (Venus,
  Uranus)
• Creation of satellites (May be our moon)
• Exchange of materials (Where did the water on
  Earth come from if most of the gases were blown
  away by solar wind after Earth was formed?)
• Catastrophes (Where did all the dinosaurs go?)

10
Where did the moons come from?

• Giant Impact
• Our moon may have been formed in a giant impact
  between the Earth and a large planetesimal
• Captured Moons
• Phobos Deimos of Mars may be captured
  asteroids.
• Triton orbits in a direction opposite to
  Neptunes rotation

Capture of Comet Shoemaker by Jupiter
11
The Age of the Solar System

• Through radioactive dating, we have determine
  that the age of the solar system is about 4.6
  billion years
• Potassium-40 (an isotope of Potassium K19)
  decays to Argon-40 by electron capture, turning a
  proton in its nuclei into neutron (thus changing
  its chemical properties)
• Potassium-40 exists naturally
• Argon is an inert gas that never combine with
  anything, and did not condense in the solar
  nebula
• By determining the relative amount of
  Potassium-40 to Argon-40 trapped in rock, we can
  determine the age of rock, assuming that there
  were no Argon-40 initially

12
Radioactive Dating Using K-40

• For every 1.25 billion years, half of the
  Potassium-40 decay and turn into Argon-40
• 1.25 billion years is called the half-life of
  Potassium-40.

13
The Formation Of Solar System Simulations
Simulations from www.astronomyplace.com. Check
them out!
History of the Solar System, Part 1
History of the Solar System, Part 2
Orbit in the Solar System, Part 4
History of the Solar System, Part 3
14
Do we Have a Viable Theory?

• YES!
• We can explain most of the properties of the
  solar system, including the exceptions.
• We used only good physics.

• Testing Our Theory against other solar system
• Can we find protoplanetary disks (before planets
  were formed)?
• Can we find other solar system?
• If we do find other solar system, does our theory
  explain the other solar system?

15
Common Characteristics and Exceptions of the
Solar System
We can explain all these in our planetary
nebular theory!
16
Evidences Of Protoplanetary Disks
Do we have any evidence of the existence of
planetary nebulae outside of the solar system?
We now have many observational evidences of the
existence of the protoplanetary Disks.
Hubble Space Telescope image of the dust disk
surrounding Beta Pictoris
Each disk-shaped blob is a disk of material
orbiting a star
17
More Protoplanetary Disks
MAUNA KEA, Hawaii (August 12, 2004) The sharpest
image ever taken of a dust disk around another
star has revealed structures in the disk which
are signs of unseen planets. Dr. Michael Liu,
an astronomer at the University of Hawaii's
Institute for Astronomy, has acquired high
resolution images of the nearby star AU
Microscopii (AU Mic) using the Keck Telescope,
the world's largest infrared telescope. At a
distance of only 33 light years, AU Mic is the
nearest star possessing a visible disk of dust.
Such disks are believed to be the birthplaces of
planets.
http//www.ifa.hawaii.edu/info/press-releases/Liu0
804.html
18
Are There Other Solar Systems Like Ours?
19
More Known Planets
20
Whats wrong with this picture?
These are all Jupiter-sized planets orbiting very
close to the star!
21
How do we Find The Extrasolar Planets?
Doppler Effect Large planets can pull the star
to move in a circular motion. Given the measured
velocity and periodicity of the star, we can
estimate the distance and mass of the planet
Direct Imaging Tough! We have not achieved this
yet!
22
An Example of Brown Dwarf (NOT A Planet)
Companion to a Sun-Like Star
http//www.ifa.hawaii.edu/users/mliu/Research/hr76
72/presswebpage/pressrelease.html
Astronomers using adaptive optics on the Gemini
North and Keck telescopes have taken an image of
a brown dwarf orbiting a nearby star similar to
the Sun.  The faint companion is separated from
its parent star by less than the distance between
the Sun and the planet Uranus ( 15 AU) and is
the smallest separation brown dwarf companion
seen with direct imaging.  The research team
estimates the mass of the brown dwarf at 55 to 78
times the mass of planet Jupiter.  The discovery
raises puzzling questions about how the brown
dwarf formed, and it adds to the surprising
diversity of extrasolar planetary systems being
found with cutting-edge observational techniques
It is very difficult to directly image an
Earth-like planet very close to its host star
23
Is The Nebular Theory OK?

• We have evidences for the existence of
  protoplanetary disks!
• We have found many extrasolar planetsby indirect
  methods.
• We have not found any solar system like ours!
• All the extrasolar planets we found so far are
  large, Jupiter-sized (or larger) planets.
• All these planets are located very close to the
  host star, inconsistent with the nebular theory.

• Why we dont find any solar system like ours?
• May be we just havent found them yet!
• Possible Explanation ? Detection Limit
• Larger planets at close distance to the host
  stars produce larger Doppler effect and intensity
  dropSmaller planets far away from the star
  produce much smaller effect, and are more
  difficult to detect.

24
But, why are these large planets so close to the
stars?

• According to our planetary nebular theory, large
  planets can only be formed far away from the host
  star, behind the frost line, where there are
  abundant quantities of gasesSo, why do we see
  these large planets so close to the stars?
• Possible Explanations?
• May be solar wind did not start or started late
  in these systems?
• Maybe these planets are formed far away from the
  stars as our planetary nebular theory predicts.
  But for some reason their host stars didnt
  develop a wind, and friction between the planets
  and the dense planetary gas (which did not get
  cleared out due to the lack of solar wind) causes
  the planets to lose their orbital angular
  momentum and migrate toward the stars.

25
Summary

• We have a viable theory to explain the formation
  of our solar system.
• We have evidences that planetary nebulae exist in
  other star systems.
• However, we have not found a solar system similar
  to ours outside of our own.
• Extrasolar planets we found so far do not agree
  with our theory The physics of our theory is
  fundamentally correct, but details of the model
  may need adjustment