Phys141 Principles of Physical Science Chapter 15 The Solar System Instructor: Li Ma Office: NBC 126...
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Transcript of Phys141 Principles of Physical Science Chapter 15 The Solar System Instructor: Li Ma Office: NBC 126...
Phys141 Principles of Physical Science
Chapter 15 The Solar System
Instructor: Li Ma
Office: NBC 126Phone: (713) 313-7028Email: [email protected]
Webpage: http://itscience.tsu.edu/ma
Department of Computer Science & PhysicsTexas Southern University, Houston
Nov. 8, 2004
Topics To Be Discussed
An Overview The Planet Earth The Terrestrial Planets The Jovian Planets and Pluto Skip §15.5 – §15.7
The Solar System
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)
Objects revolving around the Sun:– 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
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
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)
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)
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 = ?
Planets in Solar System
Terrestrial planets: inner planets– Mercury, Venus, Earth, and Mars
Jovian planets: outer planets– Jupiter, Saturn, Uranus, and Neptune
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
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)
The Earth is undergoing several motions simultaneously– The daily rotation on its axis– The annual revolution around the Sun– Procession
Rotation: spinning on an inter axis Revolution: the movement of one mass
around another
The Planet Earth (cont)
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
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)
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
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)
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 fast-moving planet
The Terrestrial Planets (cont)
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
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)
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)
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
Homework Assignment– Review Questions (page 412 – 413):
1,3,9,11,13,25,42
– Exercises (page 414): 2,4
– It’s due Monday, 11/22/04
Reading Assignment– Chapter 16