The Solar System

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The Solar System
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The Solar System
Nebula is very hot, and generally is made of gas
that is rotating.
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The Solar System
Rotation
Hot, rotating nebula

Solar Nebula
Large amount of rotation near the equator
Small amount of rotation about the axis
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The Solar System
Rotation

Large amount of rotation near the equator
Small amount of rotation about the axis
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The Solar System
Rotation

More ability to establish orbit because of large
amount of rotational speed
Gravity dominated
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The Solar System
Rotation

More ability to establish orbit because of large
amount of rotational speed
Gravity dominated flattening
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The Solar System
Rotation

More ability to establish orbit because of large
amount of rotational speed
Gravity dominated flattening
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The Solar System
Hotter
Rotation




Protoplanetary Disk The swirling, pancake
shaped mass destined to become the solar
system The sun is located at the center of the
Protoplanetary Disk.
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The Solar System
Hotter
Rotation




Within the solar nebula, hot gases contain too
much energy (recall relation between kinetic
energy and temperature.
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The Solar System The Role of Dust
New Hubble Image Reveals Details in the Heart of
the Trifid Nebula Three huge intersecting dark
lanes of interstellar dust make the Trifid Nebula
one of the most recognizable and striking star
birth regions in the night sky. The dust,
silhouetted against glowing gas and illuminated
by starlight, cradles the bright stars at the
heart of the Trifid Nebula. This nebula, also
known as Messier 20 and NGC 6514, lies within our
own Milky Way Galaxy about 9,000 light-years
(2,700 parsecs) from Earth, in the constellation
Sagittarius. This new image from the Hubble Space
Telescope offers a close-up view of the center of
the Trifid Nebula, near the intersection of the
dust bands, where a group of recently formed,
massive, bright stars is easily visible
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The Solar System The Role of Dust
Dust in the Trifid Nebula Current theories hold
that interstellar dust clouds entered the solar
nebular. The dust particles were relatively
cool, and are composed of rocky and icey matter
with a size of approximately .001 cm.
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The Solar System
Rotation


Condensation Theory Interstellar dust cools the
nebula, and the dust particles act as sites of
nucleation or condensation of the particles
around them.
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The Solar System
Rotation

As the nebula cools, gravity from the
condensation sites attract more and more
material, and the condensed grains sweep away
more and more of the material around them.
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The Solar System
Rotation

Accretion gradual growth of small objects by
collisions and sticking.
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The Solar System
Rotation

Protoplantets accumulated matter that
eventually grows into planets.
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The Solar System Temperature Profile
Rotation

Near the sun, the temperature of the condensing
solar nebula is high (a few thousand degrees K.
Further out, temperature drops to hundreds down
to tens degree Kelvin.
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The Solar System Temperature Profile
Loose discussion More massive elements will be
migrate toward the sun as a result of a stronger
gravitational pull. Lighter elements will
populate regions farther from the sun.
Temperature T a KE ½ m v2 At a given
temperature, more massive objects will move
slower, and are more likely to stick. More
massive particles can condense at the high
temperature regions near the sun, low lighter
particles will condense further from the sun.
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The Solar System Temperature Profile
Rotation

High temperatures closer to sun can condense only
heavier molecules, father away, only simpler
elements condense.
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The Solar System
As a result the higher density planets will be
closer to the sun, the lower density planets will
be further from the sun. The inner, more dense
planets are called the terrestrial planets.
These planets are earthlike Mercury, Venus,
Earth, Mars The outer, less dense planets are
called the Jovian Planets. The Jovian Planets
are Jupiter, Saturn, Uranus, Neptune Pluto is in
a category by itself
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The Solar System
Comparative Planetology the study of the
similarities and differences of the objects in
the solar system.
Stars 1 Planets 8 Dwarf Planets 3 (?
There is a potential for many more) Moons 135
(?) Large asteroids 6 Smaller asteroids Tens
of thousands Comets A whole bunch Meteors A
whole bunch
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The Solar System
The image (see next slide) is an up to date map
of the solar system displaying the orbits of the
terrestrial planets and the estimated position of
thousands of known asteroids. This diagram is
missing comets, space probes and, of course, the
undiscovered asteroids. Even conservative
estimates would suggest that for every asteroid
on a dangerous Earth-Approaching orbit there are
hundreds more which have yet to be discovered.
There are over 300 known objects on
Earth-crossing orbits, the majority of which are
potentially capable of causing death and
destruction on a scale unheard of in human
history. The terrestrial planets (Mercury, Venus,
Earth and Mars) are shown on the diagram by Cyan
or White squares, and their orbits are
represented by the blue ellipses around the Sun
(the yellow dot at the centre). The Earth is
highlighted because of its special importance to
us. Small green points mark the location of
asteroids which do not approach close to the
Earth right now. This does not exclude the
possibility that they will do so in the future
but generally we can consider the Earth to be
safe from these for the near future. Yellow
objects (with the exception of the one in the
middle which we astronomers call the Sun -) are
Earth approaching asteroids which are called
Amors after the first one discovered. Amors have
orbits which come close to the Earth but they
don't cross the Earth's orbit. However, their
orbits are close enough to the Earth that they
could potentially be perturbed by the influence
of the planets and begin to cross the Earth's
orbit in a short time. There are over 300 known
objects on such orbits. Finally the red boxes
mark the location of the Apollo and Aten
asteroids. These cross the Earth's orbit and are
the most directly identifiable astronomical
threat for the near future. Included in this
selection is the infamous asteroid, 1997XF11,
which made a major impact on the world's
headlines in March 1997 when observations
indicated that it had a good chance of colliding
with the Earth in 2028. Thankfully, new
observations were made and the newly calculated
orbit predicts a close approach of about 600,000
kilometres. Other asteroids which have orbits
which may hit the Earth are 1999 AN 10 and 1998
OX 4. Further observation is required to
determine their orbits in sufficient detail to
predict an impact or a near miss. It is
estimated that there are perhaps 100,000 to
1,000,000 undiscovered asteroids on similar Earth
crossing orbits.
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