Transcript Chapter 15 - Department Of Computer Science

Phys141 Principles of Physical Science
Chapter 15
The Solar System
Instructor: Li Ma
Office: NBC 126
Phone: (713) 313-7028
Email: [email protected]
Webpage: http://itscience.tsu.edu/ma
Department of Computer Science & Physics
Texas Southern University, Houston
Nov. 8, 2004
Topics To Be Discussed
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An Overview
The Planet Earth
The Terrestrial Planets
The Jovian Planets and Pluto
Skip §15.5 – §15.7
The Solar System
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The universe is the totality of all matter,
energy, space and time
Astronomy is the study of the universe
Solar system is a complex system of moving
masses
All these moving masses are held together by
gravitational forces
Sun: a star at the center of solar system, the
dominant mass
The Solar System (cont)
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Objects revolving around the Sun:
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9 rotating planets
over 70 satellites (moons)
thousands of asteroids
comets, meteoroids, interplanetary dust particles,
gases, and solar wind composed of charged
particles
The Model of Solar System
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Geocentric model: Earth-centered model
 Heliocentric model: Sun-centered model
 Kepler’s first law: law of elliptical paths
– All planets move in elliptical paths around the Sun
at one focus of the ellipse
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Kepler’s second law: law of equal areas
– An imaginary line (radial vector) joining a planet to
the Sun sweeps out equal area in equal periods of
time
The Model of Solar System
(cont)
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Kepler’s third law: harmonic law
– The square of the sidereal period of a planet is
proportional to the cube of its semimajor axis (one
half the major axis)
(period)2 ∞ (semimajor axis)3
T2 = kR3
– Sidereal period (T): time of one revolution with
respect to a star, the orbital period with respect to
the stars – the true period of revolution
The Model of Solar System
(cont)
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For the Earth, time of one revolution with
respect to the Sun is one year (T = 1 y)
 Astronomical Unit (AU): average distance
between the Earth and the Sun
– 1 AU = 1.5 x 108 km
So, k = 1 y2/AU3, and same for all planets
 Table 15.1 on page 384
 e.g. R = 1.52 AU, T = ?
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Planets in Solar System
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Terrestrial planets: inner planets
– Mercury, Venus, Earth, and Mars
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Jovian planets: outer planets
– Jupiter, Saturn, Uranus, and Neptune
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Pluto: does not resemble the Earth or Jupiter,
has the smallest diameter
 Prograde motion: west-to-east revolution
 Retrograde motion: east-to-west revolution
The Planet Earth
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The Earth is a solid, spherical, rocky body
with oceans and an atmosphere.
 In our solar system, the Earth is the only
planet with large amounts of surface water,
an atmosphere that contains oxygen, a
temperate climate, and living organisms
 The Earth is an oblate spheroid, fattened at
the poles and bulging at the equator
The Planet Earth (cont)
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The Earth is undergoing several motions
simultaneously
– The daily rotation on its axis
– The annual revolution around the Sun
– Procession
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Rotation: spinning on an inter axis
 Revolution: the movement of one mass
around another
The Planet Earth (cont)
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The Earth rotates eastward around a central
internal axis that is tilted 23.5° from the line
perpendicular to its orbital plane
– The Foucault pendulum is an experimental proof
of the Earth’s rotation on its axis
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The Earth revolves eastward around the Sun
– The observation of parallax
– The telescope observation of systematic change
in position of stars annually
The Planet Earth (cont)
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The 23.5° tilt of the axis and the revolution of
the Earth around the Sun are the reason for
the four seasons we experience annually
The Terrestrial Planets
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Mercury, Venus, Earth, and Mars
Relatively small in size and mass
Composed of rocky material and metals
Relatively dense and have solid surface and
weak magnetic fields
Relatively close to the Sun
None has a ring system
The Terrestrial Planets (cont)
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Only the Earth and Mars have moons
 Only the Earth has surface water and an
atmosphere that is 21% oxygen, others have
no free oxygen in their atmosphere
 Mercury: the closest planet to the Sun, has
the shortest period of revolution, is the fastmoving planet
The Terrestrial Planets (cont)
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Venus: our closest planetary neighbor, third
brightest object in the sky, exceeded only by
the Sun and our Moon
 Mars: has a reddish color when viewed from
the Earth, is the planet that most closely
resembles the Earth; unmanned spacecrafts
have been sent to Mars, a manned landing
may be sent in future
The Jovian Planets & Pluto
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Jupiter, Saturn, Uranus, and Neptune
large in size compared with the terrestrial
planets
gaseous, no solid surface, composed mainly
of hydrogen and helium
All have a very low density and have strong
magnetic fields
have many rings and moons
Very distant from the Sun with orbits far apart
The Jovian Planets & Pluto
(cont)
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Jupiter: the largest planet of the solar
system, in both volume and mass, has many
moons
 Saturn: has three prominent rings, three
spacecrafts have visited it, another is on its
way
 Uranus: has a ring system that is very thin,
has over 20 moons
The Jovian Planets & Pluto
(cont)
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Neptune: regarded as a twin to Uranus due
to their similarity in size, composition of their
atmospheres and internal structure
 Pluto: the most distant planet from the Sun,
the only planet that has not been visited by a
space probe
Assignment
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Homework Assignment
– Review Questions (page 412 – 413):
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1,3,9,11,13,25,42
– Exercises (page 414):
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2,4
– It’s due Monday, 11/22/04
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Reading Assignment
– Chapter 16