Solar System Origin and Contents
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Fundamental question: Is our solar system typical or atypical?
Planets to Scale
Scale orbital distribution click here
Terrestrial Worlds
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Small: <10,000 km radius
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Low mass: < 1 Earth
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Dense: Refractory (silicate) mantles and metallic (typically
iron) cores.
Solid (cratered) surfaces and thin atmospheres, if any
Jovian Worlds
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Large: > 10,000 km radius up to nearly 100,000 km
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“Gas” dominated, no solid surface
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Small water dominated cores; Icy satellites
Jovian Worlds
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Large: > 10,000 km radius up to nearly 100,000 km
“Gas” dominated, no solid surface; Jupiter and Saturn have
nearly “solar” composition.
Small water dominated cores, more significant for Uranus and
Neptune
Debris “Worlds”
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Two zones, one rocky one icy, of many small objects following
a size distribution consistent with collisional evolution.
Angular Momentum Common Features
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Planetary orbits all share nearly the same angular momentum
vector.
Planetary rotations also have this same direction, in many
cases.
Angular Momentum Common Features
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Planetary orbits all share nearly the same angular momentum
vector.
Planetary rotations, as well as the Sun's, also have this same
sense, in general.
The Solar System on the whole possesses memory of an
initial spin that was central to the formation process.
A History of Bombardment, Preserved
A History of Bombardment, Preserved
The Sun
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99.8% of the Solar System's mass resides in the Sun.
With a sidereal rotation period of 25 days, only a fraction of
the Solar System's angular momentum resides in the Sun.
Lsun ~ 1042
Solar Composition
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Solar elemental abundance reflects interstellar abundances
and records a history of nucleosynthesis in the Galaxy.
Hydrogen and Helium are primordial – All other elements
amount to 1%.
Terrestrial Composition
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We are the 1%!
Solar System Formation
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Must explain...
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Regular angular momentum features
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Lack of angular momentum in the Sun
Distribution of planetary composition / size with radius from Sun
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Explanation of stark compositional difference of Terrestrial planets
from Solar abundances
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Presence and structure of debris zones
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History of Solar System bombardment
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Lots of other details, particularly those preserved in
Asteroids/Meteorites.
Star Formation – A Galactic Perspective
Star Formation
Molecular Clouds
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Concentrated regions of the
interstellar medium with
density a thousand to a
million times that of
interstellar space in general
– 106/cm3.
Revealed by dust extinction
but gas is still dominant by
100:1
Ordinarily, “hard” radiation
keeps atoms in individual
form rather than in
molecules.
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4.5eV dissociates H2
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11.1eV dissociates CO
The concentration of dust
shields atoms and permits
molecule formation.
Molecular Clouds
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Hydrogen gas is in
molecular form but largely
undetectable.
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H2 is a symmetric
molecule, and producing
radiation is difficult.
Carbon monoxide,though
relatively rare, emits
strongly at millimeter
wavelengths and maps
these regions.
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CO is 10-4 times less
abundant than H2, but the
significant dipole moment
of the molecule makes its
a strong emitter.
Molecular Clouds
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Molecules can emit radiation via
rotation or vibration.
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The lowest energy is the
rotational transition from J=1
to J=0 (one unit of h-bar).
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Given the moment of inertia
of the CO molecule this
transition corresponds to a
photon of wavelength 2.6
mm (115 GHz).
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CO is a primary tool for
mapping out the dense
interstellar medium in the
Milky Way and other
galaxies.
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Oxygen has three isotopes of
increasing rarity O16, O17, O18;
carbon has two C12, C13.
Molecular Clouds
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CO is a primary tool for mapping
out the dense interstellar
medium in the Milky Way and
other galaxies.
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Oxygen has three isotopes of
increasing rarity 16O, 17O, 18O;
carbon has two 12C, 13C.
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Given the smaller “optical depth”
these trace isotopologues can
probe conditions in the densest
regions.
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Since molecules emit sharp
spectral lines the Doppler shift can
reveal detailed gas motions.
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Under very dense conditions other
molecules like HCN, H2CO, ro…
form and are tracers of cloud
collapse and ultimately planet
formation.
Molecular Clouds
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CO is a primary tool for mapping
out the dense interstellar
medium in the Milky Way and
other galaxies.
–
Oxygen has three isotopes of
increasing rarity 16O, 17O, 18O;
carbon has two 12C, 13C.
–
Given the smaller “optical depth”
these trace isotopologues can
probe conditions in the densest
regions.
–
Since molecules emit sharp
spectral lines the Doppler shift can
reveal detailed gas motions.
–
Under very dense conditions other
molecules like HCN, H2CO, ro…
form and are tracers of cloud
collapse and ultimately planet
formation.
Molecular Clouds
●
CO is a primary tool for mapping
out the dense interstellar
medium in the Milky Way and
other galaxies.
–
Oxygen has three isotopes of
increasing rarity 16O, 17O, 18O;
carbon has two 12C, 13C.
–
Given the smaller “optical depth”
these trace isotopologues can
probe conditions in the densest
regions.
–
Since molecules emit sharp
spectral lines the Doppler shift can
reveal detailed gas motions.
–
Under very dense conditions other
molecules like HCN, H2CO, ro…
form and are tracers of cloud
collapse and ultimately planet
formation.
Molecular Clouds
●
CO is a primary tool for mapping
out the dense interstellar
medium in the Milky Way and
other galaxies.
–
Oxygen has three isotopes of
increasing rarity 16O, 17O, 18O;
carbon has two 12C, 13C.
–
Given the smaller “optical depth”
these trace isotopologues can
probe conditions in the densest
regions.
–
Since molecules emit sharp
spectral lines the Doppler shift can
reveal detailed gas motions.
–
Under very dense conditions other
molecules like HCN, H2CO, ro…
form and are tracers of cloud
collapse and ultimately planet
formation.
Nearby Star Forming Regions
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The nearest region of low-mass (solar type) star formation is
in Taurus-Auriga and is 140 parsecs away.
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1 arcsecond = 140 AU - 5 times the size of Neptune's orbit.
The nearest massive star forming region is the Orion Nebula –
400 parsecs away.
Molecular Clouds
Molecular Clouds