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Key Ideas• Galaxies: clusters of stars; different shapes
• Stars: Sun; differ in size, temperature and color; source for all bright objects
• Gravity: planets, stars, solar system
• Know the appearance, composition, position and size, and motion of objects in our solar system
• Astronomical units for measuring
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What is a Meteor?
What is a Comet?
What is a Star?
What is a Nebula?
What is an Open Cluster?
What is a Black Hole?
What is a Quasar?
?
??
? ??
M33, The Pinwheel Galaxy in Triangulumby George Greaney
What is astronomy? M33, The Pinwheel Galaxy in Triangulum
by George Greaney
Basically, if its off this planet its a study of some realm of astronomy.
As one might imagine that covers an awful lot of subjects, even more than we know right now. •NGC 253, galaxy in Sculptor
by George Greaney
What is astronomy?
Astronomy is a science that attemptsto understand the make-up and the history of the universe.
Galaxy M83 in Hydraby George Greaney
•Stars •Nebula •Planets
•The Sun
•The Great Andromeda Galaxy by George Greaney
•Star clusters •Galaxies
•Galaxy clusters
•Dark matter •Black holes
Galileo Observatory in Italy
An astronomer is a scientist, skilled in mathematics, physics, and astronomy.
Most professional astronomers work for universities or government agencies.
Source: The Berkeley Cosmology Group
Astronomer Serena Kim at work At Cerro Tololo in Chili
Few astronomers spend much time looking through a telescope. Most operate telescopes from a control room or even from their computer at home via theInternet.
Typical astronomers only spend one or two weeks eachyear observing, and the rest of their research time analyzing their data.
Source: Applied Theoretical and Computational Physics DivisionLos Alamos National Laboratory
What is an amateurastronomer?
Although the term has different meanings for different people, a basic definition would include anyone who looks into the sky, and wants to see or learn more.
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The Expanding Universe 15-5
Theories on How the Universe Formed•The Big Bang Theory•Steady-State Theory and Plasma Theory
Hubble’s Law
Age of the Universe
What is space like?
• No air
• No gravity-when you’re not very close to a planet, sun, or moon
• No wind
• No friction
• No real “up” or “down”
• No pressure
What is a “galaxy”? (Textbook reference 15-4)
• A large group of stars outside of our own Milky Way• Made of billions to trillions of stars
– Also may have gas and dust
• Spiral, or elliptical, or irregular shapedImage at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and http://www.noao.edu/image_gallery/html/im0685.html
Elliptical Galaxies
Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
Irregular Galaxies
NASA and NOAO/AURA/NSF Images at http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ ,
http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
Our Galaxy: the Milky Way
• has about 200 billion stars, and lots of gas and dust
• is a barred-spiral (we think)• about 100,000 light-years wide• our Sun is halfway to the edge, revolving at
half a million miles per hour around the center of the Galaxy
• takes our Solar System about 200 million years to revolve once around our galaxy
Mapping the Milky Way
We can see
– stars
– star clusters
– nebulae
– galaxies
How do we know what our galaxy looks like?How do we know what our galaxy looks like?
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Reviewing Galaxies
• Groups of stars, planets, and space debris
• Irregular, Elliptical, Spiral
• Milky Way is our galaxy
What is a Star?
Our Sun is the closest star.
At the simplest, a star is just a ball of gasthat has condensed out of interstellar material. The largest part of its lifetime is spent as a main sequence star during which hydrogen is being converted to helium balancing gravitational contraction so that the radius and energy output remain almost constant.
Source: The British Astronomical Association
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Stars (Textbook reference 15-2 and 15-3)
• Bodies of gases that give off tremendous amounts of radiant and heat energy
• Constellations are groups of stars used for navigation, storytelling, honoring heroes
Life Cycle of a Star Video
Image courtesy of Dave DockeryAstronomical Society of Las Cruces Source: The British Astronomical Association
Nearby Stars:
Name Distance from Earth
Sun 93 million miles (8 light minutes) Proxima Centauri 4.22 Light YearsAlpha Centuri A,B 4.39 Light YearsBarnards Star 5.94 Light YearsWolf 359 7.8 Light YearsLalande 21185 8.3 Light YearsSirius A,B 8.6 Light Years
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Black Holes
• Remains of a neutron star that has collapsed due to intense gravity
• Event horizon = surface of a black hole from which light cannot escape
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Hertzsprung-Russell Diagram
The Doppler Effect:
Red Shift – stars moving away from EarthBlue Shift – stars moving toward Earth
Video on the Hertzsprung-Russell Diagram
Spectroscopy Video
Hertzsprung-Russell Diagram
Images from http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html and
http://sunearthday.gsfc.nasa.gov/2009/TTT/65_surfacetemp.php
Using a Star’s Spectrum• We can use a star’s spectrum to classify it.
NOAO/AURA/NSF image at http://antwrp.gsfc.nasa.gov/apod/ap010530.html
Time to Create a Stellar Graph
• Everyone will receive several “stars”
• Place them on the large paper, according to their color and their brightness
• This is a version of the Hertzsprung-Russell diagram.
Measuring Distances• Parallax (let’s model it)
– As Earth orbits the Sun, we see nearby stars move relative to more distant stars
– How many degrees did the plate move, relative to the background?
– Can you calculate the distance to the plate?
– The angles involved for stellar observations are very small and difficult to measure. Proxima Centauri, has a parallax of 0.77 arcsec. This angle is approximately the angle subtended by an object about 2 centimeters in diameter located about 5.3 kilometers away.
The Sun (Textbook reference 14-2
• The sun is an ordinary star.• The sun is the biggest,
brightest, and hottest object in the solar system.
• Its energy is the result of the fusion of hydrogen nuclei into helium nuclei.
• The sun is made of about 70% hydrogen and 28% helium.
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Characteristics of the Sun• Interior: Core, Radiation Zone, Convection
Zone• Exterior: Photosphere, Chromosphere,
Corona• Features: Sunspots, Prominences, Solar
Flares• Central star in our solar system around which
planets revolve• Composed of gases (H2 and He) burning at
15,000,000 o C
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The Sun: Seasons (Textbook Reference 12-1)
Seasons: Solstices
sun directly overheadtwo times a year (June 21 and December 21)June=longest day, December=shortest day
Equinoxeshalfway between solsticesneither hemisphere is tilted toward the sundaylight and darkness=equal
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What causes the seasons?
1. 23.5° tilt of Earth’s axis
2. Direct vs. indirect sun rays
3. Length of daylight
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Energy in the Atmosphere:Energy reaches earth’s atmosphere
Reflected back or absorbedclouds, dust and gasessurface
Energy is transferred within the troposphereradiation: heats land and water
reflected back into atmosphereconvection: moves heat through the troposphere
warm air is replaced by denser, cool airconduction: transfers heat from land and water directly
into the air nearest Earth’s surface
The Sun: Solar Energy (14-2)
Source: The British Astronomical Association
Our Sun is a star that has already spentabout 5 billion years on the main sequence.
Scientist believe our Sun is roughly halfwaythrough it's life.
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Phases of the Moon (Textbook reference 12-3)
waxing = increasing waning = decreasing
gibbous = > ½ crescent = < ½
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Lunar Phases
• New Moon
New
Waxing CrescentFirst QuarterWaxing GibbousFull
• Waxing Crescent
• First Quarter
• Waxing Gibbous
• Full Moon
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Lunar Phases
• Full Moon
• Waning Gibbous
• Last Quarter
• Waning Crescent
• New Moon FullWaning GibbousLast QuarterWaning CrescentNew
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Rotate vs. Revolve
• Rotation – spin of an object on its axis
• Revolution – orbit of an object around another object
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Why does one side of the moon always face us?
• Moon rotates once every 27.3 days
• Moon revolves once every 29.5 days
• Moon’s rotation approximately equal to its revolution
Stars are the source of light for all objects in outer space
• Complete the standards-based reading handed out in class to address this concept
• Answer the assessment questions that accompany the handout
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SOLAR SYSTEM
• The Sun
• Eight Planets and Pluto
• Sixty-one satellites of the planets
• Many Comets and asteroids
A collapsing interstellar cloud
• Stars and planets form from interstellar clouds
– They appear dark because of dust blocking out the light
– The light can cause it to glow, or even become heated
– Stars and solar systems are “born” this way
• Collapse accelerates
– The collapse of this cloud is slow, but it accelerates and becomes denser at the center
– This collapse and spin results in a flattening at the equatorial plane
• Matter condenses– Our solar system may have formed this way when
temperature and pressure caused hydrogen to fuse into helium
– The temperature differential allowed for different elements to concentrate in different areas around the sun
• This is why the inner planets are rocky and have a higher melting point
• Outer ones are less dense and made of ice and gas
Planetesimals
• The planetesimals combined to get larger and in many cases to become the known planets.
• Gas giants form– Jupiter was the first to form
• Icy planetesimals combined to form it
• Its mass (gravity) caused it to collect much of the debris
– The others formed the same way, but Jupiter took most of the extraneous material
• Terrestrial planets form – the merging of planetesimals in the inner portion of the disk– Made of materials that resist vaporization– Most of the gaseous material and “smaller stuff” consumed
by the sun, hence fewer satellites.
• Debris– All of the “junk” left over– Some became comets– Some ejected from solar system or destroyed in collisions– The asteroid belt between mars and Jupiter is the rest
The Greeks called the five points of light that seemed to move among the stars ______, meaning “______”. • planets• wanderers
Planets…Wandering Stars?
Greek Ideas: Earth at the Center(Textbook reference 14-1)
Initially the geocentric theory stated that everything
moved around the earth. Retrograde motion (apparent
westward movement) led astronomers to find a different
explanation
Describe the ancient Greek beliefs of the solar
system.
• The ancient Greeks thought Earth was a stationary object and the sun, moon, and planets were on a rotating celestial sphere
Checkpoint: What is a geocentric system?
• A geocentric system is one in which Earth is at the center of a system of revolving planets.
Figure 2: Interpreting DiagramsWhere is Earth located in this illustration?
• The Earth is in the middle of the solar system
• The sun, moon, and a planet are orbiting Earth on a large circle, while moving on a smaller cirlce
How is Ptolemy’s model of the solar system differ from the Greeks before him?
• The Greeks before Ptolemy thought the universe was unchanging and the sun, moon, and planets moved together on a celestial sphere (like a carousel). Earth was stationary
• Ptolemy introduced the idea of the sun, moon and planets rotating on little circles which rotate on bigger circles
Copernicus’s Idea: Sun at the Center
The heliocentric model (Copernicus) put the sun at
the center and planets in orbit around it.
Proximity to the sun caused planets to move at different
speedsThis explained retrograde
Guide For Reading: How do the heliocentric and geocentric descriptions of the solar system differ?
• In a geocentric system, Earth is at the center of the revolving planets.
• In a heliocentric system, Earth and the other planets revolve around the sun.
What two discoveries made by Galileo supported the heliocentric description of the solar system?
• Jupiter’s four moons revolve around the planet.
• Venus goes through phases similar to those of Earth’s moon.
Brahe, a ______ ______, made much more accurate observations by carefully observing the positions of
the planets for almost _____ years.
• Danish astronomer• 20
Brahe and Kepler
What did Kepler discover about the orbits of the planets?
• Kepler had discovered that the orbit of each planet is an ellipse.
• Ellipse: an elongated circle or oval shape.
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The Space Program (textbook reference 13-2)
• Space Race began in 1957 with the launch of the Soviet satellite Sputnik I– Satellite – an object revolving around another object
• Humans in Space– Soviets launched the first human in 1961
• The Moon Landing– 1969, Apollo 11, and Neil Armstrong and Buzz
Aldrin
• Kepler’s Laws
– 1st law in general, the planets orbit the sun in an ellipseThe eccentricity of the orbit is how “squashed” the orbit is
– 2nd law a line drawn from the sun to any planet, sweeps out equal areas in equal times (although the orbital distance may be different)
– 3rd law he defined the size of the ellipse and the orbital period (year)
Inertia
• Inertia: tendency of a moving object to continue in a straight line or a stationary object to remain in place.
Gravity
• Gravity: The attractive force between two objects; its magnitude depends on their masses and the distance between them.
The strength of gravity depends on the ______ of the objects and the ______ between them.
• mass• distance
Figure 5: Interpreting Diagrams -What would happen if a planet had no inertia?
• The planet would be pulled into the sun
Figure 5: Interpreting Diagrams -What would happen if a planet had no gravity?
• The planet would continue to travel straight off into space
Guide For Reading: What two factors keep the planets in their orbits?
• Newton concluded that two factors – inertia and gravity – combine to keep the planets in orbit.
• Inertia keeps the planets the moving
• Gravity from the sun keeps the planets from traveling off in space
Reviewing Gravity
• Gravity is the attractive force between 2 objects– It is affected by mass and distance
• Gravity is what determines the orbit planets follow
• Newton’s explanation of gravity supported Kepler’s laws of planetary motion.
Dark Matter helps Gravitational Pull
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Solar System Characteristics (Textbook reference 14-3)
• Inner Planets
–Mercury, Venus, Earth, Mars• Terrestrial planets with atmosphere and crust
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The Inner Planets
• Terrestrial Planets
• 4 inner planets
• Similar densities to Earth
• Solid rocky surfaces
Mercury
• closest to the sun• 1/3 Earth’s size(or the
size of Earth’s moon)• no moons• solid and covered with
craters• almost no atmosphere• the eighth largest
planet(second smallest planet)
• Surface– covered with craters and plains– the plains formed much like the maria on the moon– the craters are smaller with less ejecta
• Interior– the density suggests a dense core similar to the
Earth– the magnetic field suggests its partially molten
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Venus
• Sixth largest planet• Sister planet to Earth• About three-fourths the
size of Earth• Has no moons or rings• The brightest object in our
sky besides the sun and moon because of proximity and albedo 75%
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• Surface is rocky and very hot (covered in craters, volcanoes and mountains)
• Atmosphere completely hides the surface and traps the heat.
• Probes and satellites have provided radar images of 98% of the surface
Earth• Third planet from the sun• Fifth largest planet• Liquid covers 71 percent of the Earth’s
surface.• The Earth has one moon.• Only planet known to have life and liquid
water• Atmosphere composed of composed of
Nitrogen (78%), Oxygen (21%), and other gases (1%).
Mars
Fourth planet from the sunA thin atmosphere that contains
mostly carbon dioxideAppears as bright reddish color
in the night skySurface features volcanoes and
huge dust stormsHas 2 moons: Phobos and
Deimos
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Solar System Characteristics(Textbook reference 25-4)
• Outer Planets
–Jupiter, Saturn, Uranus, Neptune, Pluto• Jovian planets have ring systems and gas atmospheres
(J, S, U, N)• Pluto is neither terrestrial or Jovian
The Outer Planets(Textbook reference 14-4)
• The Gas Giants
• These planets include: Jupiter, Saturn, Uranus and Neptune
• All larger than Earth by 15-300 times
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Jupiter
• The largest planet (1/10 of the sun and 11X Earth’s)
• Better than 70% of the planetary mass of the solar system
• 52% albedo
• Has a banded appearance
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Jupiter
• Rings have 3 parts: Halo Ring, Main Ring, Gossamer Ring
• Brightest planet in sky• Strong magnetic field• 60+ moons, 5 visible from
Earth
Density is relatively low for its sizeThe is because of it composition (H and He in gas or
liquid form.
RotationShortest day in the solar system about 10hrs
This fast spin distorts the shapeThis also contributes to its banded appearance
Belts are low lying dark-colored cloudsZones are high light-colored clouds
MoonsMore than 60, but some are very smallMostly composed of ice and rock
Gravity assist 107
Jupiter’s Red Spot
• “the great spot” is a storm of swirling gas that has lasted for better than 300 years
• Jupiter does not have a solid surface. The planet is a ball of liquid surrounded by gas.
Moons of Jupiter
Jupiter has four large Galilean moons, twelve smaller named moons and twenty-three more recently discovered but not named moons.
We’ll take a look at the four large Galilean moons which were first observed by Galileo in 1610.
Io– Io is the fifth moon of
Jupiter. It’s the third largest of Jupiter’s moons.
– Io has hundreds of volcanic calderas. Some of the volcanoes are active.
Europa• Europa is the sixth of
Jupiter’s moons and is the fourth largest.
• It is slightly smaller than the Earth’s moon.
• The surface strongly resembles images of sea ice on Earth. There may be a liquid water sea under the crust.
• Europa is one of the five known moons in the solar system to have an atmosphere.
Ganymede• Ganymede is the
seventh and largest of Jupiter’s known satellites.
• Ganymede has extensive cratering and an icy crust.
Callisto• Callisto is the eighth of Jupiter’s known satellites and
the second largest.• Callisto has the oldest, most cratered surface of any
body yet observed in the solar system.
Saturn
• Second largest planet • Sixth from the sun.• Slightly smaller than Jupiter• Easily visible in the night sky• Voyager explored Saturn and its rings.• Made of materials that are lighter than water. (If you
could fit Saturn in a lake, it would float!)
Rings of Saturn• 7 major rings made up of ringlets• Gravity keeps the rings in place• rings are not solid• composed of small countless
particles• rings are very thin.• Though they’re 250,000 km or
more in diameter, they’re less than one kilometer thick
• Moons• 55 moons• 31 moons
– Largest moon, Titan,
• Titan, the largest is bigger than Mercury
• Odd among moons because of content with dense atmosphere and methane’s existence in 3 states
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Uranus• 7th planet from sun• Has a faint ring system (they are dark and hard to observe)• 27 known moons• Covered with clouds• Uranus sits on its side with the north and south poles
sticking out the sides.• 4x larger and 15Xmass of the Earth
• AtmosphereBluish appearance cause by methane gasClouds are similar in appearance to the
surfaceLiquid surface with a small solid core
• RotationAlmost a top to bottom rotationPoles vacillate between 42 years of darkness
and light
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Uranus
Norm Herr (sample file)
URANUS
• Uranus has more moons (15) than any other planet except Jupiter (16) and Saturn (23)!
0
5
10
15
20
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Number of Moons
MercuryEarthMarsJupiterSaturnUranusNeptunePluto
Neptune
• 4th largest planet• 8th planet from sun
– Because of the orbits, from 1979 to 1999, Neptune was the ninth planet.
• Discovered through math• 7 known moons• Great Dark Spot thought to be a hole, similar to
the hole in the ozone layer on Earth• Like Uranus, the methane gives Neptune its
color.
Neptune• Atmosphere
– Smaller and denser than Uranus but 4XEarth– Similar in color to Uranus (twins??) but does have
some color variation on surface– Belts and zones give it texture
• Moons and Rings– 13 moons Triton being the largest
• Triton has retrograde orbit
• Also has nitrogen geysers when heated by the sun
• Rings are invisible from Earth but exist
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Note the apparent storms
The blue coloration of Neptune is probably due to the presence of methane
Pluto…a planet?
• Today, Pluto is called a "dwarf planet.“
• A dwarf planet orbits the sun just like other planets, but it is smaller.
• A dwarf planet is so small it cannot clear other objects out of its path.
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Per NASA.gov.
• In 2003, an astronomer saw a new object beyond Pluto. The astronomer thought he had found a new planet. The object he saw was larger than Pluto. He named the object Eris (EER-is).
Finding Eris caused other astronomers to talk about what makes a planet a "planet." There is a group of astronomers that names objects in space. This group decided that Pluto was not really a planet because of its size and location in space. So Pluto and objects like it are now called dwarf planets.
Pluto is also called a plutoid. A plutoid is a dwarf planet that is farther out in space than the planet Neptune. The three known plutoids are Pluto, Eris and Makemake (MAH-kee-MAH-kee). Astronomers use telescopes to discover new objects like plutoids.
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Dwarf Planet Pluto
• Pluto, is one of three plutoids.
• It is a small (smaller than Earth’s moon), solid and icy
• It is so far from the sun that it has never been visited by spacecraft.
• It orbits the sun very slowly.
Sample Quiz Questions
Question: Which of the planets are rocky?
Answer: The inner planets: Mercury, Venus, Earth and Mars
Image by Dave DockeryAstronomical Society of Las Cruces
Comet Ikeya Zhang
What Are Comets, Asteroids and Meteors? (textbook reference 14-5)
Space Debris
CometsA comet is basically a ball of ice and dust in space. The typical comet is less than 10 kilometers across. Most of their time is spent frozen solid in the outer reachesof our solar system.
Image by Harvard-Smithsonian Center for Astrophysics
Comet Hale Bopp
A comet orbits around the sun, in a wide, elliptical path. When a comet gets within a few million miles of the sun, it begins to melt, leaving a tail of gas and dust that is blown by solar winds
Image by Harvard-Smithsonian Center for Astrophysics
Source:NASA
Comet Hale Bopp
Reviewing Comets
• Small icy bodies
• Travel past the Sun
• Give off gas and dust as they pass by
• Tail of gasses called a coma
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Asteroids
• Asteroid – rocks orbiting in space
• Asteroid belt – 100,000 asteroids located between Mars and Jupiter
–separates inner and outer planets
Asteroids
• Small bodies
• Believed to be left over from the beginning of the solar system billions of years ago
• Largest asteroids have been given names
Meteoroids
• Meteoroid – smallest asteroids or comets
– Come from asteroids colliding in space
– Come from a comet breaking up and creating a cloud of dust continuing to move through the solar system
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Meteors
• Meteor – meteoroid striking Earth’s atmosphere
• Meteorite – meteor that hits Earth’s surface
Solar SystemActivities
• Order the Planets
• Fun with Planets
• Constellations of the Northern Sky
• Planets
• Solar System
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Units of Time from Space
• Year – 1 revolution of Earth
• Day – 1 rotation of Earth
• Month – 1 revolution and/or rotation of Moon
Measuring Distances• What is a Light Year?
– A light year is the distance light travels in a year. Light moves at a velocity of about 300,000 kilometers (km) each second; how far would it move in a year?
– About 10 trillion km (or about 6 trillion miles).
• Why do we use light years?– Show me how far 5 centimeters is.
– Now show me 50 centimeters.
– Now tell me (without thinking about it, or calculating it in meters) how far 500 centemeters is. 2000? 20,000?
– We need numbers that make sense to us in relationship to objects; we scale up and use meters and kilometers for large numbers.
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Measurements in Space
• Light year – distance light travels in one Earth year
• Astronomical Unit – distance from Earth to Sun
http://www.youtube.com/watch?v=3bmb0YE9VGM