Star

A large, glowing ball of gas hat generates heat and light through nuclear fusion

Planet

A moderately large object that orbits a star, it shines by reflected light. These may be rocky, icy, or gaseous in composition

Moon or Satelite

An object that orbits a planet

Asteroid

A relatively small and rocky object that orbits a star

Comet

A relatively small and icy object that orbits a star

Solar (Star) System

A star and all the material that orbits it, including its planets and moons

Nebula

An interstellar cloud of gass and/or dust. Stars can form out of these

Galaxy

A great island of stars in space, all held together by gravity and orbiting a common center

Universe

The sum total of all matter and energy that is, everything within and between all galaxies

Distance light travels

distance                        light travel time

sun                                  8 min.

Sirius                              8 years

Andromeda galaxy             2.5 million years

Light year

The distance ligh can travel in one year

about 10 trillion km or 6 trillion miles

Observable Universe

As far away as we can see

Our Physical Place in the Universe

Earth→solarsystem→ milkey way→ local group→ local supercluster

How we came to be

The matter in our bodies cam from the Big Bang, which produced hydrogen and helium and the trace element Lithium

All other elements were constructed from H and He in stars and then recycled into new star systems, including our solar system

Past Universe

When we look to great distances we are seeing events that happened long ago because light travels at a finite speen

looking back in time

Size of the Milky Way

• has about 100 billion stars
• about 100,000 lightyears across
• we are 28,000 light years or half way out

Constellation

A region of the sky, within official borders set in 1928 by the IAU

• often recoganizable by a pattern or grouping of stars
• some of the stars are close and others are far away
• many different societies have seen the same groupings but have given them different names

Constellation

the patterns of stars have no physical significance

Modern day astronomers use them as landmarks

The Celestial Sphere

• The sky above looks like a dome
• if we imagine the sky around the entire earth we have this
• this is a 2D representation of the sky
• represents the view from earth

North and South Celestial Poles

The points in the sky directly above the earth's north and south poles

Celestial Equator

extension of the earth's equator onto the celestial sphere

Ecliptic

annual path of the sun through the celestial sphere, which is a projection of the eliptic plane

The Milky Way

• Shaped like a disk
• our solar system in in that disk
• when we are looking at this we are looking along that disk

Measuring the Sky

• We measure the sky in angles not distances
• full circle =360°
• 1° =60 archmin
• 1archmin= 60 archsec

Zenith

The point directly above you

Horizon

all points 90° from the zenith

Altitude

angle above the horizon

Meridian

Straight north through the zenith to straight south

Latitude

position north or south of equator

Longitude

Position east or west on the prime miridian

Circumpolar

A star that you can see all the time

Stars that never set

Annual Motion

• As the earth orbits the sun, the sun appears to move eastward with respect to the stars
• the sun circles the celestial sphere once every year
• this path is called the ecliptic

Ecliptic

The sun circles the celestial sphere once every year

Cause of Seasons

Caused by the Earth's axis tilt, not the distance from the earth to the sun

Earth's Axis

Always paints in the same direction

Causes the seasons

Summer

The days are longer resulting in more time for the sun to heat the earth

July and Aug. are typically hotter then June

Seasons

When the earth goes around the sun; since the earth's axis is tilted parts of the earth get more sun then other parts

Waxing moon

starts on right side of moon

moon gets fuller

• new (dark)
• crescent
• first quarter
• gibbous
• full

Waining Moon

gets dark on right side of moon

becoming less

• full
• gibbous
• last quarter
• crescent

Gibbous

when the moon is 3/4 full

waining or waxing

Same face of the moon

rotational period (moon rotates) = orbital period

                                                 (orbits planet)

Tides

The moons gravity gently tugs at the earth causing these

Lunal Eclipse

when the earth's shadow falls on the moon

• moon becomes red because the sunlight "mixes"
• The world's sunsets are hitting the moon

Node

where plane of orbit and other plane cross

Only happens in 2 places

Solar Eclipses

When the new moon blocks the sun

Occurs during the day

Moon is just big enough to completly cover the sun

Copernicus

• proposed sun-centered model (1543)
• Used model to determine layout of the solar system (planetary distences in AU)
• Predicted planitary motions in perfect circles

Tycho

• Compiled most accurate naked eye measurments ever made of planetary position
• Still could not detect stellar varallax, and thus still thought earth must be at the center of the solar system

Kepler

• Hired by Tycho
• first tried to match Tycho's observations with circular orbits
• But 8archmin discrepancy led him to eliptical orbits instead of perfect circles

Kepler's 1st Law

The orbit of each planet around the sun is an ellipse with the sun at one focus

Kepler's 2nd Law

As a planet moves around its orbit, it sweeps out equal areas in equal times

this means that the object travels faster when it is nearer to the star and slower when it is further away

Kepler's 3rd Law

More distant planets orbit the sun at slower average speeds

The further out it is the longer it takes to go around the sun

Nature of Motion

• Galileo's experiments showed that objects in air would stay with a moving earth
• Showed that objects will stay in motion unless a force acts to slow them down

Heavenly Perfection

Sunspots on the sun (imperfections)

mountains and valleys on the moon (proving that it was not a perfect sphere)

Parallex

the stars are too far away

they do not jump back and forward as we move

saw the milkey way has countless individual stars

Speed

Rate at which an object moves

Speed=distance/time

m/s

Velocity

Speed and direction

m/s^2

Acceleration

Any change in velocity

Newton's 1st Law of Motion

An object moves at a constent velocity unless a net force acts to change its speed or velocity

Newtons 2nd Law of Motion

force= mass X acceleration

Newton's 3rd Law of Motion

For every force, there is always an equal and opp. reaction force

Conservation of Momentum

Total momentum of interacting objects cannon change unless an external force is acting on them

Interacting objects exchange momentum through = and opp forces

Conservation of Angular Momentum

explains why objects rotate faster as they shrink in radius

Thermal Energy

The collective kinetic energy of many particles

related to temp. but is no the same thing

Temperature

the avg. kinetic energy of the many particles in a substance

Mass- Energy

mass itself is a form of potential energy

a small amount of mass can release a great deal of energy

Changing an Orbit

friction or atmospheric drag

a gravitational encounter

Emission

gives off light

Absorbtion

take light in

Transparent

objects transmit light

Opaque

objects that block (absorb) light

Photon

particles of light

Wavelength

distance between 2 wave peaks

Frequency

number of times per second that a wave vibrates up and down

Ionization

Stripping of electrons, changing atoms into plasma

Dissociation

Breaking of molecules into atoms

Evatoration

Breaking of flexable chemical bonds, change liquid to gas

Melting

Breaking of chemical bonds, changing from solid to liquid

 Continus Spectra

the spectrum of a common light (incandescent) bulb, spans all visible wavelenghts without interruption

Emission Line Spectrum

A thin or low-density cloud of gas emits light only at specific wavelenghts that depend on its composition and temp., producing a spectrum with bright emissions

Absorbtion Line Spectrum

a cloud of gas between us and a light bulb can absorb light of specific wavelengths leaving dark absorbtion lines in the spectrum