Download (SNT): The Origin of Our Solar System

The Origin of Our Solar System
Part 1
Survey of the solar system
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What do you know (or think you know)?
• Confer with your tablemate (or people in front
or back of you) and write down some things
you think you know about our solar system.
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Solar Nebula Theory (SNT): Quick
Summary
• According to SNT, stars form in massive, dense
clouds of molecular hydrogen called giant
molecular clouds(GMC), which are the result
of supernovas.
• These clouds are gravitationally unstable, and
matter coalesces into smaller, denser clumps
inside.
• These clouds collapse and form stars. This can
give birth to planets.
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Solar Nebula Theory (SNT)
• While originally applied to our solar system, it
applies to all solar systems.
• The formation of planetary systems is thought
to be a natural result of star formation.
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Testing the Solar Nebula Theory
• Astronomers search the present solar system
for evidence of the past – using physics,
chemistry, geology, and biology.
• We are going to compile a list of our solar
system’s most significant characteristics that
are potential clues on how it formed.
• For the Solar Nebula Theory (SNT) to be
successful, it must explain all of the
phenomena we encounter.
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Planets Revolve Around the Sun
• Planets revolve around the sun in orbits that
lie close to a common plane.
– Except for Mercury which is inclined 7% to Earth’s
orbit, all of the other planets are inclined no more
than 3.4%.
– As you can see, the solar system is flat and disk
shaped (next slide).
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Artists Rendition of the Disk
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Rotation and Revolution of Planets
• Rotation of the sun and planets on their axes
also seems related to the rotation of the disk.
– There is a preferred rotational direction –
counterclockwise (with the exceptions of Uranus
and Venus).
• All planets revolve counterclockwise around
the sun.
– Almost all of the solar system’s moons also revolve
counterclockwise around their planets.
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Questions
• For the Solar Nebula Theory (SNT), what must it
explain?
• How is the fact that the planets revolve around
the sun in a common plane support for the Solar
Nebula Theory?
• In what direction do all planets revolve and in
what direction do most of the planets rotate?
What are the exceptions? Conjecture as to how
the exceptions might have occurred.
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The two kinds of planets
• A clue to the formation of the solar system
comes from the division of the planets into
two groups: terrestrial and Jovian planets.
• The 2 kinds of planets are distinguished by
location.
– Four inner terrestrial planets are very different
from the 4 outer Jovian planets.
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The two kinds of planets
Frost line is 150 degrees Kelvin or
negative 190 degrees Fahrenheit.
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The two kinds of planets
• Craters are common on almost every solid
surface in solar system (SS).
• The 2 groups are also distinguished by
properties such as presence or absence of
rings and numbers of moons.
• The planets have evolved since their
formation, so other evidence is necessary.
– Clues can be found in the smaller objects in solar
system.
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Distinctions
• The differences between Jovian and terrestrial
planets is “dramatic.”
• The inner four planets are rocky, small, and
dense worlds with little or no atmosphere.
• Jovian planets, outer planets, are low-density
with thick atmospheres and liquid or ice
interiors.
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Distinctions
• Orbits
– Terrestrial planets lie quite close to sun.
– Jovian planets are spread far from the sun.
Orbits
to
scale
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Distinctions
• Earth is the most massive of the terrestrial
planets but is much less massive compared to
the Jovian planets.
Planets and sun
to scale. Jupiter
is over 300 “Earth
masses” and
Saturn over 100
Earth masses.
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Distinctions
• Terrestrial planets have rock and metal-like
densities.
• Jovian planets have low densities and
“Saturn’s density is only 70% that of water and
would float in a big enough bathtub.”
• The Jovian planets’ atmospheres are turbulent
and often marked by great storms, like
Jupiter’s Great Red Spot.
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Distinctions
• All four Jovian Planets have ring systems.
– Jupiter, Uranus, and Neptune’s rings are from dark
rocky particles.
– Saturn’s rings are made of ice particles.
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Distinctions
• Jovian interiors contain small cores of heavy
metals surrounded by liquid.
– Jupiter and Saturn contain hydrogen in a liquid
state due to high pressure.
– Uranus and Neptune contain heavy-element cores
surrounded by partially solid water mixed with
rocks and minerals.
• Jovian planets have extensive moon systems.
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“Space Debris”
• Space debris is also a product of the solar
nebula.
• Three types of debris:
1. Asteroids
2. Comets
3. Meteroids
• They represent a small fraction of SS’s mass
but are important sources of information
about the planets.
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Asteroids
• Small rocky worlds – most orbit sun in a best
between Mars and Jupiter.
• >100,000 asteroids have charted orbits.
– About 2,000 have paths that bring them into the
inner solar system (creating collision possibilities).
• Asteroids are not planets that have broken
apart (like was once hypothesized) but are
debris left over from the failure of a planet to
form at 3 AU (90,000,000 miles) from the sun.
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Asteroids
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Asteroids
•
•
•
•
200 asteroids are >60 miles in diameter.
10s of 1000s are >6 miles in diameter.
>1,000,000 that are >0.6 miles in diameter.
Asteroid surfaces are rocky and metallic.
– Photographs from a robotic spacecraft show
asteroids as irregularly shaped and covered with
craters.
• Rocks, metals, and collisions played a major
role in the SS’s formation.
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Craters
• As already stated, craters are common on all
surfaces in the solar system strong enough to
retain them (i.e. on terrestrial planets).
• Earth has about 150 impact craters, though
many have been erased by erosion (we are
finding new ones).
• When astronomers see a rocky or icy surface
with few craters, know the surface is young.
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Impact Crater in Arizona
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Size and Ages of Some Craters
• Vredefort , Free State, South Africa, 300km diameter,
2023 millions of years old
• Sudbury Ontario, Canada, 250 km diameter, 1849
million years old
• Chicxulub, Yucatán, Mexico, 180 km diameter, 65
million years old
• Kara, Nenetsia, Russia 120 km, 70.3 million years old.
• Manicouagan, Quebec, Canada, 100 km diameter 215
million years old.
• Popigai, Siberia, Russia 100 km diameter, 35.7 million
years old.
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Kuiper Belt
• In 1992 >1,000 small, dark, icy bodies orbiting the
outer fringes of the solar system, beyond
Neptune, were discovered (named after Gerard
Kuiper who predicted their existence in the
1950s).
• There are probably >100,000,000 bodies larger
than 1 km (0.6 miles) in the Kuiper Belt (KB).
• For the Solar Nebula Theory, or any theory to be
successful, it must explain how the KB came to
be.
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Kuiper Belt
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Comets
• Comets can occasionally be visible to the
naked eye as they fly through the inner solar
system.
• They appear as glowing balls with an extended
tail of gas and dust.
• Comet nuclei are ice-rich bodies – a few kms
to 10s of kms in diameter.
– They are left overs from the origin of the planets
(called “dirty snowballs” or “icy mudballs).
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Comets
• From comets, can conclude the solar nebula
had abundant icy materials.
• Comets appear as they do because as they fly
toward the sun, the sun’s heat vaporizes the
ice, releasing gas and dust (creating the tail).
• A comets tail can be longer than an AU.
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Comets
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Rosetta
• What is Rosetta?
• What is Rosetta’s mission?
• What do we hope to learn from Rosetta?
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Meteors (shooting stars)
• Flash across the sky in momentary streaks of
light.
• They are small bits of rock and metal colliding
with Earth’s atmosphere and bursting into
incandescent vapor because of friction with
the air about 50 miles above the Earth (just
inside of the space Earth boundary).
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Meteors
• In space, before arriving to our atmosphere,
they are called meteoroid.
• Any part that makes it to Earth’s surface is
known as a meteorite.
• Most meteoroids are dust, grains of sand, or
pebbles.
– Most meteors we see are from meteoroids that
weigh less than 1 gram.
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Meteors
• Few meteoroids are massive enough to
survive the plunge to Earth’s surface (though it
does happen and sometimes with spectacular
effects).
• Video from Russian meteorite:
https://www.youtube.com/watch?v=W4N_Fp
Ecxk4
• Meteorites are effective in aging the SS.
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Meteorites
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Perseid Meteor Shower time lapse
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Orion Nebula – Star Formation
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