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Unit 2
The Earth in Space
The Solar System
Origin of Our Solar System
Today, most astronomers believe our solar
system is a by-product of the origin of the
sun.
The most accepted explanation is the
Nebular Hypothesis
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Immanuel Kant, a German philosopher first
proposed in 1755
Terms Related to the Hypothesis
Nebula which is an immense cloud of gas
and dust particles
Planetesimals which are small rocky
objects that rotate around a star
Accretion is the process of growth by
accumulation
Protosun was the predecessor of the Sun
Nebular Hypothesis
5 billion years ago
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The solar system was believed to have consisted of a
nebula
This nebula was slowly rotating and due to some unknown
cause, it began to contract under its own gravitational pull.
The largest mass accumulated in the center, attracting
more dust particles and gas. The areas left behind
formed a series of whirlpools
The center area grew smaller (matter packed in) and the
spinning increased.
Example: Think of a figure skater who pulls their arms into a spin.
What happens when they extend their arms?
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The result: The cloud was flattened into a disk-like shape
The collapsing, spinning nebula begins
to flatten into a rotating pancake
Nebular Hypothesis cont’d
100 million years later
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Majority of mass accumulated in center
In the whirlpools areas, planetesimals were forming
through the process of accretion. As dust and gas
were pulled inward, these planetesimals grew in
size increasing in gravitational pull.
This pull was strong enough to hold lighter gases like
hydrogen and helium
This process took about 10 to 30 million years to form the
present size of today’s planets
Nebular Hypothesis cont’d
The pressure of the center mass increased to such
levels that the inner temperature of the PROTOSUN
reached 11 million oC
Result:
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Thermonuclear explosion which was the lighting of the
Sun’s inner core
T. Tauri Wind, a solar wind of charged particles
Traveled at speeds of 3.3 million km/h throughout the solar system
for 9 million years
Swept away all gas and dust particles between the planets
Stripped the inner planets of their first atmosphere
The outer planets held their helium and hydrogen atmospheres
Nebular Hypothesis cont’d
In the last 4.5 billion years
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The planetesimals continued to collide with other planets
and moons adding to their masses
It’s important to recognize that only the largest of these
planetesimals could survive the high-energy collisions
from meteorites (lower mass planetesimals)
These traveled at 30,000 to 75, 000 km/h
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Asteroids are considered to be left-over planetesimals
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Why didn’t these asteroids make up a planet?
The Asteroid Belt between Mars and Jupiter is thought
to be remnants of material that made up the solar
system. It’s placement is such that there is competing
pull between Jupiter and the Sun
Nebular Hypothesis:
Explains Major Features of Solar System
1.
Explains regular motions of the planets and moons
•
2.
All revolve in the nearly the same plane, in nearly circular
orbits, and nearly all rotate in the nearly same direction as the
Sun too
Explains all major differences between terrestrial and
gaseous (jovian) planets
•
3.
Mass, distance from Sun, composition, moon and ring systems
Explains small bodies
•
4.
Asteroids and comets, both short- and long-period
Explains exceptions to the trends
•
Terrestrial moons, axial tilts, non-coplanar jovian moons,
Triton
Nebular Hypothesis:
Current Challenges to the Nebular Hypothesis
1. Missing mass in Kuiper Belt
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Icy bodies found beyond orbit of Neptune
2. Capture process for Triton
•
Largest moon of Neptune orbits in opposite
direction
3. Sideways rotation of Uranus
4. Discovered “hot Jupiter” exoplanets
•
These planets are much closer to their parent star
then our own Jupiter
5. Discovered exoplanets in binary and trinary
stellar systems
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Planets with two / three parent stars
Kuiper Belt
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Disk shaped region of 100’s of icy objects beyond orbit of Neptune
http://www.cnes.fr/imagezoom.php?file=p1135_ed77069b38b89947b9f6e5678e9af2adkuiper_pluton.jpg&label=Ou
ter+solar+system+and+Kuiper+Belt.+Credits%3A+NASA
Difficult to Prove
It’s important to remember that this hypothesis is
the best explanation to date for the formation of
a solar system.
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It is not yet possible to observe the formation of the
other stars to verify the steps outlined (Think
distance)
No one was around for the first one
It is believed that if this hypothesis is true that all
solar systems would form the same way – use
the same pattern
Ways of proving this is through technology
Nebular Hypothesis
http://www.youtube.com/watch?v=PL3YN
QK960Y
Instrumentation
Expanding our Knowledge of the Solar System
To improve our understanding of the Solar
System technological developments
include:
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19th Century
Optical telescopes
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20th Century
Radio telescopes
Rocketry
Telescopes
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Hubble
Technology
(4 minutes)
Videos\Space_Travel__The_International_
Space_Station.asf
Hubble Space Telescope
(2 minutes)
Videos\Understanding_the_Universe__Th
e_Hubble_Space_Telescope.asf
Hubble Space Telescope (HST)
The HST must be able to talk with controllers
on the ground to relay data from its observations
and receive commands for its next targets.
To communicate, the HST uses a series of
relay satellites called the Tracking and Data
Relay Satellite System (TDRSS), which is the
same system used by the International Space
Station.
Sequence of Events:
Incoming light from an object gets received by the HST (2) and converted to
digital data. The data is then sent to the TDRSS in orbit (3), which then
transmits it to the Ground Receiving Station at White Sands, N.M. (4). The
White Sands Facility transmits the data to NASA's Goddard Spaceflight
Control Center (5), where HST operations are centered. The data are then
analyzed by scientists at the nearby Space Telescope Science Institute in
Baltimore, MD. (6). Most of the time, commands are relayed to the HST in
advance of a planned observing run; however, real-time commands are
possible when necessary.
Hubble Space
Telescope
Photo courtesy NASA / STScI
Communications system used
by the Hubble Space Telescope.
Recent Hubble Space Telescope observations shed
considerable light on the birth of stars and associated
planetary systems.
Regions in the Orion
Nebula where solar
systems appear to be
forming
1500 light years from
Earth
Middle star in the
sword of the
constellation Orion
This image shows
several protoplanetary
disks.
Think About
Voyager 2 Satellite
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Gone 12 years
Jupiter, Saturn, Uranus, Neptune
Information doubled what was known about
the solar system
Problem
It will take decades to get through all the
information