Transcript The Solar System & Stars

Man must rise above Earth, to the top of the
atmosphere and beyond; for only then will he fully
understand the world in which he lives. Socrates
The Earth and Other Planets
Science 2201
Chapter 16
“morning stars”
& wanderers
Geocentric Solar System
Heliocentric Model
Solar System
Figure 16-1
Most of the mass in the solar system is in the Sun, and most of
the rest is in the Jovian planets. (Distances in this figure are not
to scale.)
The Sun and its Planets
• Planets and moons tend to orbit about the
sun in a counterclockwise direction
• Orbits of planets and their moons are in the
same general plane
• Planets and moons tend to rotate on their
axis in counterclockwise direction
Solar System
The Nebular Hypothesis
• theory for origin of solar system
• rotating nebula had formed gaseous rings
which condensed into the planets and
moons, with the nebula’s nucleus forming
the sun p. 323
Figure 16-2
As the nebula that formed the solar system collapsed, it began to
rotate and flatten into a disk. The stages in solar system formation
include (a) a slowly rotating nebula, (b) a flattened disk with
massive center, (c) planets in the process of birth represented as
mass concentrations in the nebula, and (d) the solar system.
The Planets
Mercury (.39 au)
Small, rocky, airless world with
an extreme climate!
• Mariner 10, did 3 flybys 1974-75
• Years & Days: “fastest planet”
– Orbital period = 88 Earth days
– Rotation period = 59 Earth days
• Planet of Extremes
– Day temp’s exceed 800oF
– Night temp’s drop to –280oF
• Surface:
– Almost doubles as the moon. Mercury contains impact craters
ranging from ½ mile to one over 800 miles wide. Ridges and
basins filled with cooled lava fill the picture.
Venus (.72 au)
A forbidding yet fascinating world
of scorching temp’s, rocky plains,
& huge volcanoes.
• Data from 17 landing probes & 18 flyby
Spacecraft (Pioneer of ‘78 & Magellan of ’93)
• An Out-of-Control Greenhouse Effect
– 30-mile thick atmosphere of CO2 generates surface pressure
100X Earth’s and traps heat, sustaining temp’s > 800oF.
• Slow and Backward Planet
– Venus rotates very slowly, once every 243 Earth days
– Venus orbits the sun every 225 Earth days, so on Venus, a day is
longer than a year!
– Spins not from west to east, like the other planets, but from east
to west. Perhaps an asteroid collision set Venus on a backward
rotation.
Earth (1 au)
The very special “third rock.”
Hospitable Home Planet
• Vast oceans of liquid water and protective atmosphere
rich in oxygen.
• Orbits in stable, nearly circular path, so never too far or
too close to the Sun
• One Moon—large by solar system standards—acts to
stabilize Earth, preventing tilt from shifting wildly.
• Oceans of water absorb and transfer heat, regulating
global temperatures.
• Precious envelope of air serves as a breathable, protective
blanket.
Mars (1.52 au)
The red planet, our nearest neighbor.
• Observed by Mariner 9, ‘71, Viking ‘77,
And Pathfinder spacecraft of 1997
• An Unearthly World
– Thin atmosphere (like Earth’s at 140,000 ft) of 95% CO2
– Elliptical orbit accentuates seasonal differences—temp range
from –190oF to 62oF
– Dry, desolate surface, but tilted axis gives it polar ice caps
– 2 small moons: Deimos & Phobos—may be captured asteroids
– Olympus Mons – 13 mile high volcanoe the size of Arizona!
– Valles Marineris – system of canyons up to 4 miles deep forms an
immense gash 2500 miles across.
Asteroids
Tens of thousands of small rocky bodies orbit
the sun in a large area between Mars and
Jupiter. (asteroids, or better, planetoids)
• Thought to be
material that failed to
become a planet
during formation of
solar system.
Asteroids
Rocks in space through which the Earth
passes as it travels around the Sun.
• Meteors may be tiny
grains of sand or may
be very large.
• Billions enter Earth’s
atmosphere each year,
encounter friction
some 50 miles
overhead and burn
white hot.
• If lands = meteorite.
Meteors
The Planets
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