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Chapter 1-5

Chapter 1-5 Midterm Study Guide!!!

12 Pages
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Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
C.B.Netterfield

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AST101 – The Sun and Its Neighbours
Midterm #1 – Study Notes
Chapter 1 – 5
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Chapter 1 Our Place in the Universe
GEOCENTRIC earth-centered universe
SOLAR SYSTEM (star system) consists of a star (sometimes more than one star) and
all the objects that orbit it [consists of the Sun and all the objects that orbit it: the
planets and their moons, asteroids (chunks of rocks), comets, and countless tiny particles
of interplanetary dust]
MILKY WAY Used both as the name of our galaxy and to refer to the band of light we
see in the sky when we look into the plane of the Milky Way Galaxy
GALAXY a huge collection of anywhere from a few hundred million to more than a
trillion stars, all bound together by gravity
LOCAL GROUPthe group of more than 30 galaxies to which the Milky Way Galaxy
belongs
GALAXY CLUSTERS (cluster of Galaxies) a collection of a few dozen or more
galaxies bound together by gravity; smaller collections of galaxies are simply called
groups (groups of galaxies with more than a few dozen members)
SUPERCLUSTERS consists of many clusters of galaxies, groups of galaxies, and
individual galaxies and are the largest known structures in the universe
LOCAL SUPERCLUSTER the Supercluster of galaxies to which the Local Group
Belongs
UNIVERSE the sum total of all energy and matter
BIG BANG The event that gave birth to the universe
LIGHTYEARS the distance that light can travel in 1-year, about 9.46 trillion km/6
trillion miles !ONE LIGHTYEAR
OBSERVABLE UNIVERSE the portion of the entire universe that we can potentially
observe (consists only of objects that lie within 14 billion light-years)
ASTRONOMICAL UNIT (au) equivalent to about 150 million km
ECLIPTIC PLANE the plane of the Earth’s orbit around the Sun
AXIS TILT 23.5 degrees in relation to ecliptic plane
Chapter 2 Discovering the Universe for Yourself
CONSTELLATION a region in the sky; 88 official constellations cover the celestial
sphere
CELESTIAL SPHERE the imaginary sphere on which objects in the sky appear to
reside when observed from Earth – shows us how stars appear to be arranged in the sky
(constellations)
North Celestial Pole the point directly over Earth’s North Pole
South Celestial Pole The point directly over Earth’s South Pole
Celestial Equator a projection of Earth’s equator into space, makes a
complete circle around the celestial sphere
www.notesolution.com
Ecliptic the path the Sun follows as it appears to circle around the
celestial sphere once each year
ECLIPTIC PLANE the plane of the Earth’s orbit around the Sun
LOCAL SKY the sky as seen from wherever you happen to be standing
HORIZON the boundary between the Earth and the sky
ZENITH the point directly overhead (has an altitude of 90degrees BUT NO
DIRECTION because it is straight overhead)
MERIDAN an imaginary half circle stretching from the horizon due south, through the
zenith, to the horizon due north
AZIMUTH (DIRECTION) direction along the horizon (used to pinpoint the position of
any object in the local sky) " N E S W
ALTITUDE (above the horizon) ANGLUAL distance between the horizon and the
object in the sky
ANGULAR SIZE/DISTANCE a measure of the angle formed by extending imaginary
lines outward from our eyes to span an object (or between two objects)
- SIZE angle of an object that it appears to span in your field of view
- DISTANCE the angle that appears to separate a pair of objects
CIRCUMPOLAR stars that always remain above the horizon for a particular latitude
CHAPTER 4 – Making Sense of the Universe
SPEED the rate at which an object moves. Its units are distance divided by time, such
as m/s or 100 km/hr (s=d/t)
VELOCITY the combination of speed and direction of motion; it can be stated as speed
in a particular direction, such as 100km/hr due north
ACCELERATIONthe rate at which an object’s velocity changes. Its standard units are
m/s! (change in velocity speed/direction/both)
ACCELERATION OF GRAVITY the acceleration of a falling object (abbreviated
g=9.8m/s!)
MOMENTUM the product of an object’s mass and velocity
(MO=MASS*VELOCITY)
FORCE anything that can cause a change in momentum (ONLY way to change
momentum)
NET FORCE overall force to which an object responds; the net force is equal to the
rate of change in the object’s momentum (NF = MASS*ACCELEATION)
ANGULAR MOMENTUM momentum attributable to rotation of revolution (circular
movements); the angular momentum of an object moving in a circle of radius r is the
product m*V*r
ROTATIONAL ANGULAR MOMENTUM
ORBITAL ANGULAR MOMENTUM
TORQUEa twisting force that can cause a change in an object’s angular momentum
MASS amount of matter in your body
WEIGHT the net force that an object applied to its surroundings (humans on Earth –
weight = mass*acceleration of gravity)
FREE FALL falling without any resistance to slow you down
WEIGHTLESS a weight of zero, occurs during free-fall
www.notesolution.com
NEWTON’S LAWS OF MOTION three basic laws that describe how objects respond
to forces
LAW OF CONSERVATION OF MOMENTUM the principle that, in the absence of
net force, the total momentum of a system remains constant
LAW OF CONSERVATION OF ANGULAR MOMENTUM the principle that, in the
absence of net torque (twisting force), the total angular momentum of a system remains
constant
LAW OF CONSERVATION ENERGY the principle that energy (including mass-
energy) can be neither created nor destroyed, but can only change form one form to
another
UNIVERSAL LAW OF GRAVITATIONlaw expressing the force of gravity between
two objects
1) every mass attracts every other mass through the force of gravity
2) the strength of the gravitational force attracting any two objects is
DIRECTLY PROPORTIONAL to the product of their masses (e.g. doubling
the mass of one object doubles the force of gravity between the two objects)
3) the strength of gravity between two objects decreases with the SQUARE of
the distance between their centers (e.g. doubling the distance between two
objects weakens the force of gravity by a factor of 2 ! or 4)
KEPLER’S LAWS OF PLANETARY MOTION three laws that describe the motion of
the planets around the sun
1) the orbit of each planet about the Sun is an ellipse with the Sun at one
focus
2) as a planet moves around its orbit, it sweeps out equal areas in equal
times a planet moves faster when it is closer to the Sun than when it is
farther from the Sun in its orbit
3) the square of a planet’s orbital period is proportional to the cube of its
average distance from the Sun more distant planets move more slowly in
their orbits
BOUND ORBITS orbits in which an object goes around another object over and over
again (ellipse and circles)
UNBOUND ORBITS paths that bring an object close to another object just once
(hyperbolas and parabolas)
CENTER OF MASS the point at which two or more orbiting objects would balance if
they were somehow connected; it is the point around which the orbiting objects actually
orbit the mass lies closer to the more massive object (sun in the case of the sun and
earth)
CHAPTER 5 – Light and Matter
POWER rate of energy flow
WATTS the standard units of power
JOULES the standard units of energy
SPECTRUM (electromagnetic spectrum) the complete spectrum of light (radio waves,
infrared, ultraviolet, visible light, x-rays, gamma rays)
4 Ways Light Can Interact With Matter:
www.notesolution.com

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Description
AST101 The Sun and Its Neighbours Midterm #1 Study Notes Chapter 1 5 Chapter 1 Our Place in the Universe GEOCENTRIC earth-centered universe SOLAR SYSTEM (star system) consists of a star (sometimes more than one star) and all the objects that orbit it [consists of the Sun and all the objects that orbit it: the planets and their moons, asteroids (chunks of rocks), comets, and countless tiny particles of interplanetary dust] MILKY WAY Used both as the name of our galaxy and to refer to the band of light we see in the sky when we look into the plane of the Milky Way Galaxy GALAXY a huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity LOCAL GROUP the group of more than 30 galaxies to which the Milky Way Galaxy belongs GALAXY CLUSTERS (cluster of Galaxies) a collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups (groups of galaxies with more than a few dozen members) SUPERCLUSTERS consists of many clusters of galaxies, groups of galaxies, and individual galaxies and are the largest known structures in the universe LOCAL SUPERCLUSTER the Supercluster of galaxies to which the Local Group Belongs UNIVERSE the sum total of all energy and matter BIG BANG The event that gave birth to the universe LIGHTYEARS the distance that light can travel in 1-year, about 9.46 trillion km6 trillion miles ONE LIGHTYEAR OBSERVABLE UNIVERSE the portion of the entire universe that we can potentially observe (consists only of objects that lie within 14 billion light-years) ASTRONOMICAL UNIT (au) equivalent to about 150 million km ECLIPTIC PLANE the plane of the Earths orbit around the Sun AXIS TILT 23.5 degrees in relation to ecliptic plane Chapter 2 Discovering the Universe for Yourself CONSTELLATION a region in the sky; 88 official constellations cover the celestial sphere CELESTIAL SPHERE the imaginary sphere on which objects in the sky appear to reside when observed from Earth shows us how stars appear to be arranged in the sky (constellations) North Celestial Pole the point directly over Earths North Pole South Celestial Pole The point directly over Earths South Pole Celestial Equator a projection of Earths equator into space, makes a complete circle around the celestial sphere www.notesolution.com Ecliptic the path the Sun follows as it appears to circle around the celestial sphere once each year ECLIPTIC PLANE the plane of the Earths orbit around the Sun LOCAL SKY the sky as seen from wherever you happen to be standing HORIZON the boundary between the Earth and the sky ZENITH the point directly overhead (has an altitude of 90degrees BUT NO DIRECTION because it is straight overhead) MERIDAN an imaginary half circle stretching from the horizon due south, through the zenith, to the horizon due north AZIMUTH (DIRECTION) direction along the horizon (used to pinpoint the position of any object in the local sky) N E S W ALTITUDE (above the horizon) ANGLUAL distance between the horizon and the object in the sky ANGULAR SIZEDISTANCE a measure of the angle formed by extending imaginary lines outward from our eyes to span an object (or between two objects) - SIZE angle of an object that it appears to span in your field of view - DISTANCE the angle that appears to separate a pair of objects CIRCUMPOLAR stars that always remain above the horizon for a particular latitude CHAPTER 4 Making Sense of the Universe SPEED the rate at which an object moves. Its units are distance divided by time, such as ms or 100 kmhr (s=dt) VELOCITY the combination of speed and direction of motion; it can be stated as speed in a particular direction, such as 100kmhr due north ACCELERATION the rate at which an objects velocity changes. Its standard units are ms (change in velocity speeddirectionboth) ACCELERATION OF GRAVITY the acceleration of a falling object (abbreviated g=9.8ms) MOMENTUM the product of an objects mass and velocity (MO=MASS*VELOCITY) FORCE anything that can cause a change in momentum (ONLY way to change momentum) NET FORCE overall force to which an object responds; the net force is equal to the rate of change in the objects momentum (NF = MASS*ACCELEATION) ANGULAR MOMENTUM momentum attributable to rotation of revolution (circular movements); the angular momentum of an object moving in a circle of radius r is the product m*V*r ROTATIONAL ANGULAR MOMENTUM ORBITAL ANGULAR MOMENTUM TORQUE a twisting force that can cause a change in an objects angular momentum MASS amount of matter in your body WEIGHT the net force that an object applied to its surroundings (humans on Earth weight = mass*acceleration of gravity) FREE FALL falling without any resistance to slow you down WEIGHTLESS a weight of zero, occurs during free-fall www.notesolution.com
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