Transcript The Solar System - North Salem Schools

The Solar System
Observing the Solar System
• The first astronomers
made important
observations:
– Star Trails
– “Wandering Stars”
– Models of the Solar
System
– Orbits
• The stars appear to move
across the sky in
predictable patterns.
• In the Northern hemisphere,
the sky appears to rotate
around “Polaris” – The
North Star
Star Trails
“Wandering Stars”
• These stars appeared to change position.
• Planet- means wondering star in Greek
• The Romans
later named
them:
• Mercury,
Venus, Mars,
Jupiter, Saturn
Models of the Solar System
• The early Greek
astronomers though that
the Earth was the center
of the universe:
– Geocentric – the earth is
the center of all revolving
planets
• Ptolemy (140 A.D.)
explained the motions of
the planets as they
moved around Earth
– Retrograde motion
Heliocentric
• In the 1500’s
Copernicus created
the heliocentric model
– the Sun at the
center
– “Helios” means sun in
Greek
• This better explain the
motions of the
Planets
Our solar system now has eight bona fide planets and
three "dwarf planets" (Illustration: NASA/JPL)
Contributions
• Some astronomers who
made important
contributions to the study
of our solar system:
–
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–
–
–
–
Ptolemy
Copernicus
Galileo
Brahe
Kepler
Newton
• Galileo –
– Used a telescope to prove
the heliocentric model
– Observed Venus’ phases
• Brahe and Kepler
– Accurate observations to
figure out the shapes of the
planets orbits - ellipses
• Newton
– Concluded that two factors,
inertia and gravity,
combine to keep the
planets in orbit
Elliptical orbits
• From the work of Brahe and Kepler we
know that the orbits made by the planets
are not circular – rather they are oval Ellipses
Inertia and Gravity
• Inertia- the tendency
of an object in motion
to remain in motion
– The more mass the
more inertia
• Gravity is a force
between two masses
• A planet’s orbit is
based on the
balance between
inertia and gravity
The Planets
What is a planet?
• A planet is a
celestial body that
orbits a star and
does not give off its
own light.
• There are two
groups of planets;
– Terrestrial
– Gaseous
Terrestrial Planets
• Terrestrial planets
are small, solid,
and rocky
• They are the first
four planets from
the Sun:
– Mercury
– Venus
– Earth
– Mars
Mercury
• Is about the size of
Earth’s Moon
• Has no moons of
its own
• Studied and
photographed by
the Mariner
missions
• Has no
atmosphere
Venus
• Shines very brightly and
can be seen in the early
morning or early evening
• About the same size as
Earth, no moons
• Has a highly pressurized
atmosphere that
experiences a green
house effect
• Rotates (very slowly)
opposite from other
plants – east to west
• Studied and
photographed by the
Magellan missions
Earth
• Has an
atmosphere that
can support life
• Has one moon
• It over 70% water
• Contains a layered
interior
Mars
• aka “the Red Planet”
• CO2 atmosphere
• Has ‘frozen’ polar ice
caps
• Has a tilted axis like earth
– so it has seasons
• Has two small moonsPhobos and Deimos
• Studied by the Viking
missions, Mars
Pathfinder, Sojourner,
and Surveyor
The Outer Planets
• Gaseous Planets (or
Jovian) – made
almost entirely of
gasses
– Jupiter, Saturn,
Uranus, Neptune
• Dwarf Bodies – the
small, rocky, icy
planets that include
Pluto and beyond…..
– Pluto, UB313 (Xena)
Ceres,
Structure of Gas Giants
• The first four outer
planets are much larger
than Earth and made
almost entirely of gases.
– Jupiter, Saturn, Uranus,
Neptune
• Have more mass, so
exert higher gravitational
forces
• Possible solid cores….
• All have a ring system
Jupiter
• 300x more massive
than Earth
• Atmosphere is
banded in color
– Contains the “Great
Red Spot”
• Over 17 moons
• Galilean Moons: Io,
Callisto, Europa,
Ganymede
Io
Callisto
Europa
Ganymede
• Beautiful ring system
• Less dense than water
• 18 moons
– Titan is larger than Earth’s Moon
Saturn
Uranus
• Looks bluish due to
traces of methane
• Axis is tiled 90°
• 21 moons
– Mostly ice
Neptune
• Contains visible
clouds
• Has a storm similar
to Jupiter's; The
Great Dark Spot
• 8 moons
– Triton is the
Largest
Triton
Dwarf Bodies
• Smaller planets
beyond the gas giants
• Rocky, Icy worlds
• Includes:
– Pluto, Ceres, UB 313