Unit 8 astronomy 09 10
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Astronomy
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Astronomy The scientific study of matter in
outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena.
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Forget the big bang, tune in to the big hum
THE big bang sounded more like a deep hum than a bang, according to an analysis of the radiation left over from the cataclysm. Physicist John Cramer of the University of Washington in Seattle has created audio files of the event which can be played on a PC. "The sound is rather like a large jet plane flying 100 feet above your house in the middle of the night," he says. Giant sound waves propagated through the blazing hot matter that filled the universe shortly after the big bang.
These squeezed and stretched matter, heating the compressed regions and cooling the rarefied ones. Even though the universe has been expanding and cooling ever since, the sound waves have left their imprint as temperature variations on the afterglow of the big bang fireball, the so-called cosmic microwave background. Cramer was prompted to recreate the din- last heard13.7 billion years ago- by an11-year-old boy who wanted to know what the big bang sounded like for a school project.
To produce the sound, Cramer took data from NASA's Wilkinson Microwave Anisotropy Probe. Launched in 2001, the probe has been measuring tiny differences in the temperature between different parts of the sky. From these variations, he could calculate the frequencies of the sound waves propagating through the universe during its first 760,000 years, when it was just 18 million light years across. At that time the sound waves were too low in frequency to be audible. To hear them, Cramer had to scale the frequencies 100,000 billion billion times.
Nevertheless, the loudness and pitch of the sound waves reflect what happened in the early universe. During the 100-second recording (http://www.npl.washington.edu/AV/BigBangSound_2.wav), the frequencies fall because the sound waves get stretched as the universe expands. "It becomes more of a bass instrument," says Cramer.
###
Author: Marcus Chown
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The universe started as a single point. That point was extremely dense. It became unstable and exploded outward. Today the universe continues to expand.
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The Universe A massive explosion occurred, between 12 –15 billion years ago, and the universe has been expanding ever since
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Evidence for Expansion
The Doppler Effect is used as evidence that galaxies are moving away from us.
When light moves away, it’s wavelength is expanded (gets longer), meaning it becomes redder.
This is called the redshift.
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Doppler Effect
All galaxies show redshift in their spectra, meaning they are moving away from us.
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Measuring Distance
Distances between celestial objects are extremely large.
Rather than miles, astronomers refer to a light-year as a standard unit of distance.
One light-year is the distance light travels in one year.
The speed of light is 186,000 mps (300,000 kps). Thus, one light-year is about 6 trillion miles. The nearest star to us (Proxima Centauri) is 4.2
light-years away.
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Astronomical unit
Another unit of distance is the Astronomical Unit (AU).
One AU is the distance from the Earth to the Sun (93 million miles)
Distances to other objects are given in multiples of AU.
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1. 384,000 km 2. 1 AU 3. 100 AU 4. 1 light year 5. 75,000 light years
What is (approximately) the size of the solar system?
Remember:
1 AU = distance Sun – Earth = 150 million km
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Galaxies
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Galaxies
A galaxy is a collection of millions or billions of stars.
Galaxies can be spiral, elliptical, spherical or irregular in shape.
The Sun is part of the Milky Way galaxy, which is a spiral galaxy.
The Sun is located on one of the spiral arms, far from the galactic center.
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Put these in order of size:
galaxy solar system universe
universe galaxy solar system
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Regents Question Which sequence correctly lists the relative
sizes from smallest to largest?
(1)our solar system, universe, Milky Way Galaxy
(2)our solar system, Milky Way Galaxy, universe
(3)Milky Way Galaxy, our solar system, universe
(4)Milky Way Galaxy, universe, our solar system
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Regents Answer
(2)our solar system, Milky Way Galaxy, universe
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Astarisahuge,shiningballinspacethatproducesalargeamountoflightandenergy.
Starscomeinmanysizes. About75%areapartofgroupsthatorbiteachother. Theyaregroupedinlargestructurescalledgalaxies.(MilkyWay).
Starshavelife-cycleslikehumans. Astarscolordependsonsurfacetemperature.
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Stars
Stars are burning masses of gas. Their energy is the result of nuclear
fusion, in which Hydrogen atoms combine to form Helium atoms, releasing energy.
Electromagnetic energy is radiated by stars.
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Star Characteristics
Stars vary in their size, mass, density, temperature and composition.
Luminosity – the actual brightness of a star
Luminosity depends only a star’s size and temperature
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Composition
Stars are primarily made of Hydrogen and Helium
Many other elements are present in stars in small amounts
A star’s composition can be determined by spectral analysis.
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Spectral Analysis
Spectral analysis is the study of the electromagnetic spectrum emitted by a star, using a spectroscope.
Each element emits radiation is a specific set of wavelengths
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Electromagnetic Spectrum
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Color and Temperature
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ESRTs p15
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ESRTs p15
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What type of star is our Sun classified as? ESRT p15
Circle where it is on the chart
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The H-R Diagram
The Hertzsprung-Russell (H-R) Diagram is a graph of stars, comparing luminosity and temperature.
Stars are categorized according to these two properties
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The H-R Diagram
Main Sequence – band into which most stars fall – High temperature, high luminosity – Low temperature, low luminosity
Red Giants and Supergiants – cooler, very luminous stars that are very large
White Dwarfs – hotter, low luminosity stars that are small
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Shade the chart where all of the stars are hotter than our sun.
Draw a line on the chart which separates those stars brighter
than our sun and those less bright.
ESRTs p15
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The H-R Diagram
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Regents Question Which statement describes the general
relationship between the temperature and the luminosity of main sequence stars?
(1) As temperature decreases, luminosity increases.
(2) As temperature decreases, luminosity remains the same.
(3) As temperature increases, luminosity increases.
(4) As temperature increases, luminosity remains the same.
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Regents Answer
(2) As temperature increases, luminosity increases.
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Regents Question
Compared to other groups of stars, the group that has relatively low luminosities and relatively low temperatures is the
(1)Red Dwarfs (3)Red Giants (2)White Dwarfs (4)Blue Supergiants
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Regents Answer
(1)Red Dwarfs
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Regents Question Which list shows stars in order of
increasing temperature?
(1)Barnard’s Star, Polaris, Sirius, Rigel. (2)Aldebaran, the Sun, Rigel, Procyon
B. (3)Rigel, Polaris, Aldebaran, Barnard’s
Star. (4)Procyon B, Alpha Centauri, Polaris,
Betelgeuse.
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Regents Answer
(1)Barnard’s Star, Polaris, Sirius, Rigel.
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Star Life Cycles
Stars are born in a cloud of gas and dust, called a nebula.
Most stars remain as main sequence stars, until their hydrogen fuel is depleted
An average star, like the sun, would go through the Red Giant phase, eventually becoming a White Dwarf.
A large star would become a Supergiant, then explode as a supernova. The result may be a neutron star, pulsar or black hole.
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Sun
http://en.wikipedia.org/wiki/Image:Sun920607.jpg
Mythology The Sun God. Greeks Called it Hellos
Mass 333 400 times the mass of the Earth
Diameter 1 392 000 km (109 x Earth’s
diameter)
Gravity 28 times that on Earth
Surface Temperature 6000°C (average). From 4500 to
2000000°C up to 15000000°C in the core.
Period of rotation (day)
Equator 26 Earth days, poles 37 Earth days
Tilt of axis 122°
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Solar System Components
The Solar System includes: • The Sun, a medium size, middle-aged
star • The eight planets and associated moons • Asteroids – chunks of rock found mostly
in a belt between Mars and Jupiter • Comets – mass of frozen gas and rock • These are considered celestial objects
which appear in the sky during day and night.
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Formation of the Solar System 4.6 Billion years ago a large cloud of gas, ice & dust
existed Began to contract & slowly rotate
– Contraction increased density & rotation – Gravity began to pull material toward the center – Density increases = increased rotation & gravity – Begins to form disk with large center – Central mass begins to heat up due to contraction
• Temperatures reach 10 million 0K • Hydrogen atoms begin to fuse together forming
Helium • Fusion occurs, driving the formation of our Sun
– The material outside the central mass forms planets
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The Parts of Our Solar System The sun is the center of the Solar System
– Inner Planets: Also called Terrestrial planets: first four planets. They are solid, rock like structures
– Asteroid belt: band of rocks orbiting the sun – Outer Planets: Also called Jovian planets: The 4
planets farthest from the sun • 4 are made up of mainly lighter element gases • Last two are frozen materials
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Two Kinds of Planets Planets of our solar system can be divided into
two very different kinds:
Terrestrial (earthlike) planets: Mercury, Venus, Earth, Mars Jovian (Jupiter-like) planets: Jupiter,
Saturn, Uranus, Neptune
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Size of Terrestrial Planets Compared to Jovian Planets
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Terrestrial Planets
Four inner planets of the solar system
Relatively small in size and mass (Earth
is the largest and most massive)
Rocky surface
Surface of Venus can not be seen directly from Earth because of its
dense cloud cover.
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The Jovian Planets Much larger in mass
and size than terrestrial planets
Much lower average density
All have rings (not only Saturn!)
Mostly gas; no solid surface
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Asteroids
The total mass of all the asteroids is less than that of the Moon.
-rocky objects with round or irregular shapes
lie in a belt between Mars and Jupiter
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The Asteroid Belt
Plut
o
(Distances and times reproduced to scale)
Most asteroids orbit the sun in a
wide zone between the orbits of Mars
and Jupiter.
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Asteroids – Believed to be a planet that never formed – Range in size from dust to almost Moon size – Photographed by Galileo probe
• Some Named Asteroids: – Ceres: 940 km (Largest known) – Pallas: 523 km – Vesta: 501 km – Juno: 244 km – Gaspra & Ida
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only visible when they are close to
the sun
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Comets
Mostly objects in highly elliptical orbits, occasionally coming close to the sun.
Icy nucleus, which evaporates and gets blown into space by
solar wind pressure.
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Comet Information: Comet Composition:
– Dust, rock, frozen methane, ammonia, and water – Comets normally look like dirty snowballs – When they get close to stars, they change
• They begin to vaporize & Glow • Forms a coma (tail) from the nucleus (head)
– Coma: glowing trail of particles – Always points away from the star
– Comets eventually break up into space debris Oort Cloud: large collection of comets beyond
Pluto
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Meteoroids Small (µm – mm sized)
dust grains throughout the solar system
If they collide with Earth, they evaporate in the
atmosphere.
Visible as streaks of light (“shooting stars”):
meteors.
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LARGEST METEORITE TO HIT EARTH – Namibia, Africa
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Meteoroids, Meteors, & Meteorites Meteoroids: chunks of rock
– Randomly moving through space – Usually leftover comet or asteroid debris
Meteor: Meteoroid that enters Earth’s atmosphere – Heat up & begin to glow = shooting star – Most burn up before reaching the surface – Many meteors at one time = meteor shower
Meteorite: Meteor that does not totally burn up, & strikes the Earth’s surface – Impact creates a crater
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Cosmic Collision Video Clip
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http://solarsystem.jpl.nasa.gov/multimedia/gallery/solarsys_scale.jpg (Distance between objects not to scale)
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How small are we?
source: Celestia (application) (Distance between objects not to scale)
Earth
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Earth
How small are we?
source: Celestia (application) (Distance between objects not to scale)
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Relative distance of planets Sun = 1300mm
diameter (blown up garbage bag)
Mercury = 4.5mm (coffee bean) 54m from Sun
Venus = 11.3mm (small blueberry) 101m from Sun
Earth = 11.9mm (small blueberry) 139m from Sun
Mars = 6mm (pea) 213m from Sun
image source: Google Earth
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Relative distance of planets Jupiter = 133.5mm
(large grapefruit) 727m from Sun
Saturn = 112.5mm (large orange) 1332m from Sun
Uranus = 47.7mm (Kiwi) 2681m from the Sun
Neptune = 46.2mm (nectarine) 4200m from the Sun
Pluto = 2mm (grain of rice) 5522m from the Sun
image source: Google Earth
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Relative distance of planets Jupiter = 133.5mm
(large grapefruit) 727m from Sun
Saturn = 112.5mm (large orange) 1332m from Sun
Uranus = 47.7mm (Kiwi) 2681m from the Sun
Neptune = 46.2mm (nectarine) 4200m from the Sun
Pluto = 2mm (grain of rice) 5522m from the Sun
image source: Google Earth
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A planet is a body that is in orbit around the Sun, has enough mass for its self-gravity to overcome forces (nearly round) shape, and clears the neighborhood around its orbit.
Planet order (closest to the sun to furthest): MERCURY VENUS EARTH MARS JUPITOR SATURN URANUS NEPTUNE
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Position: Closest planet to the Sun. Atmosphere: Like Earth’s moon, very little. Landscape: Many craters, a little ice. Cliffs
and valleys present. Temperatures: Super-heated by the sun in
the day. At night temperatures reach hundreds of degrees below freezing. (Not as warm as you would think).
Year (Full rotation around the sun): 88 days. Moons: 0 Rings: 0
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Mercury
http://en.wikipedia.org/wiki/Image:Reprocessed_Mariner_10_image_of_Mercury.jpg
Mythology God of travel, commerce and
thieves
Mass 0.056 times that of Earth
Moons None
Diameter 4878 km ( = 0.38 x Earth’s
diameter)
Surface Similar to Earth’s moon
Gravity 0.38 times that on Earth
Surface Temperature –170°C to 430°C
Period of rotation (day) 59 Earth days
Tilt of axis 0°
Distance from Sun 0.39 AU (58 million kilometres)
Time to orbit Sun (year)
88 Earth days
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Position: 2nd planet from the sun. Atmosphere: Thick enough to trap heat,
hurricane winds, lightning, and acid clouds. Landscape: Volcanoes and deformed mountains. Temperatures: Intense heat. Year (Full rotation around the sun): 225 Earth
days. Moons: 0 Rings: 0
Venus
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Venus
http://en.wikipedia.org/wiki/Image:Venus-real.jpg
Mythology Goddess of love and beauty
Mass 0.815 times that of Earth
Moons None
Diameter 12 103 km ( = 0.95 x Earth’s
diameter)
Surface Extensive cratering, volcanic
activity.
Gravity 0.9 times that on Earth
Surface Temperature 460°C
Period of rotation (day) 243 Earth days
Tilt of axis 30°
Distance from Sun 0.72 AU (108 million kilometres)
Time to orbit Sun (year)
225 Earth days
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Position: 3rd planet from the sun. Atmosphere: Suitable air pressure to
have life. Air is made of oxygen. Landscape: The only planet that has
liquid on the surface, rocky, land formations.
Temperatures: Suitable for life. Ranges from locations on Earth.
Year (Full rotation around the sun): 365 Earth days.
Moons: 1 Rings: 0
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Earth
http://en.wikipedia.org/wiki/Image:The_Earth_seen_from_Apollo_17.jpg
Mythology Gaia—mother Earth
Mass 1.0 times that of Earth (5 980 000
000 000 000 000 000 000 kg)
Moons One (‘the Moon’)
Diameter 12 756 km
Surface Two-thirds water, one-third land
Gravity 1.0 times that on Earth
Surface Temperature average 22°C
Period of rotation (day) 1 Earth day
Tilt of axis 23.5°
Distance from Sun 1 AU (150 million kilometres)
Time for light to reach Earth
8 minutes
Time to orbit Sun (year)
365.25 Earth days
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Position: 4th planet from the sun.
Atmosphere: Thinner air than Earth.
Landscape: Frozen water below the surface, rocky, dusty, and has craters.
Temperatures: Like Earth, but drier and colder
Year (Full rotation around the sun): 687 Earth days.
Moons: 2 Rings: 0
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Mars
http://en.wikipedia.org/wiki/Image:2005-1103mars-full.jpg
Mythology God of war
Mass 0.107 times that of Earth
Moons 2 (Phobos—diameter 23 km,
Deimos—diameter 10 km)
Diameter 6794 km ( = 0.53 xEarth’s
diameter)
Surface
Soft red soil containing iron oxide (rust). Cratered regions, large volcanoes, a large canyon and
possible dried-up water channels.
Gravity 0.376 times that on Earth
Surface Temperature –120°C to 25°C
Period of rotation (day) 1.03 Earth days
Tilt of axis 25.2°
Distance from Sun 1.52 AU (228 million kilometres)
Time to orbit Sun (year)
687 Earth days
Time to reach Mars 9 months
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Position: 5th planet from the sun.
Atmosphere: Colorful clouds, until it is squished unto liquid. Cold and windy, giant storms.
Landscape: Thick super hot soup.
Temperatures: Extremely cold at clouds. Extremely hot and cold radiation.
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Jupiter
http://en.wikipedia.org/wiki/Image:Jupiter.jpg
Mythology Ruler of the Gods
Mass 318 times that of Earth
Moons
At least 28 moons and four rings, including the four largest moons:
Io, Ganymede, Europa and Callisto. These are known as the ‘Galilean’
moons.
Diameter 142 984 km ( = 11.21 x Earth’s
diameter)
Surface Liquid hydrogen
Gravity 2.525 times that on Earth
Surface Temperature Cloud top –150°C
Period of rotation (day) 9 hours 55 minutes
Tilt of axis 3.1°
Distance from Sun 5.2 AU (778 million kilometres)
Time to orbit Sun (year)
11.8 Earth years
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Position: 6th planet from the sun. Atmosphere: Composed mostly of gas
with no solid surface. Cloud strips. Landscape: No solid surfaces, high
pressures turn gas into liquids. Temperatures: Rings made out of water
ice, really cold.
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Saturn
http://en.wikipedia.org/wiki/Image:Saturn_from_Cassini_Orbiter_%282007-01-19%29.jpg
Mythology God of agriculture
Mass 95.184 times that of Earth
Moons At least 30 moons and rings in
seven bands
Diameter 120 536 km (= 9.45 x Earth’s
diameter)
Surface Liquid hydrogen
Gravity 1.064 times that on Earth
Surface Temperature –180°C
Period of rotation (day) 10 hours 39 minutes
Tilt of axis 26.7°
Distance from Sun 9.6 AU (1400 million kilometres)
Time to orbit Sun (year)
29.5 Earth years
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Position: 7th planet from the sun.� Atmosphere: Gets thicker and
thicker, until it is squished unto liquid. Cold and windy.�
Landscape: Layer of superheated water and gases that form bright clouds.�
Temperatures: Extremely cold at cloud tops and superheated towards the center.�
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Uranus
http://en.wikipedia.org/wiki/Image:Uranusandrings.jpg
Mythology Father of Saturn
Mass 14.54 times that of Earth
Moons At least 21 moons and 11 rings
Diameter 51 200 km (= 4.01 x Earth’s
diameter)
Surface Likely to be frozen hydrogen and
helium
Gravity 0.903 times that on Earth
Surface Temperature –220°C
Period of rotation (day) 17 hours 14 minutes
Tilt of axis 98°
Distance from Sun 19.2 AU (2875 million kilometres)
Time to orbit Sun (year)
84 Earth years
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Position: Furthest from the sun (Cannot see without a Telescope). 8th planet.
Atmosphere: Very Windy, cold clouds, a layer of methane gas (giving it a blue color), storms as large Earth.
Landscape: Scientist think it may have an ocean of super hot lava.
Temperatures: Cold
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Neptune
http://en.wikipedia.org/wiki/Image:Neptune.jpg
Mythology God of the sea
Mass 17.15 times that of Earth
Moons 8 moons and 5 rings
Diameter 49 528 km ( = 3.88 x Earth’s
diameter)
Surface Frozen hydrogen and helium
Gravity 1.135 times that on Earth
Surface Temperature –220°C
Period of rotation (day) 16 hours 7 minutes
Tilt of axis 29.3°
Distance from Sun 30.1 AU (4500 million kilometres)
Time to orbit Sun (year)
165 Earth years
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Pluto is NOT considered a planet anymore!
It is classified as a dwarf planet.
Temperatures: Extremely cold, covered with frost.
Year (Full rotation around the sun): 248 Earth years.
Moons: 3 Pluto is very hard to
see, if with a really powerful teloscope.
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The planets to scale. The rings of the gas giants are not shown.
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http://www.solarviews.com/cap/misc/obliquity.htm
Comparing tilt of axis
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Draw a line across the table between the terrestrial and jovian planets and label.
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Which are more dense? Jovian or terrestrial
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Which have more moons ? Jovian or terrestrial
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Which have longer periods of revolution? Jovian or terrestrial
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Which are larger in size on average ? Jovian or terrestrial
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Which planet has the longest day?
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Which planet has the longest year?
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Regents Question
Which object in our solar system has the greatest density?
(1) Jupiter (3) the Moon (2) Earth (4) the Sun
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Regents Answer
(2) the Earth
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1. What is the solar system (what objects make up the Solar System?
2. Draw a diagram of planet placement and list the planets in order from the closest to the furthest from the sun.
3. When did the solar system form? 4. When did the universe form? 5. What is the difference between the Jovian and
Terrestrial planets? 6. What is the difference between a meteor,
meteoroid, and meteorite? 7. What is your favorite planet and why?
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Planetary Orbits
Plut
o
Earth
Venus Mercury
Do Now:
Make 3 observations about this animation
(Distances and times reproduced to scale)
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http://solarsystem.jpl.nasa.gov/multimedia/gallery/vis_orb.jpg
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http://solarsystem.jpl.nasa.gov/multimedia/gallery/outer_orb.jpg
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How the planets move All planets move in the same
plane (a large imaginary flat surface)
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Tipped over by more than 900
Mercury and Pluto: Unusually highly inclined orbits
Planetary Orbits
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Planetary Orbits
Plut
o
Earth
Venus Mercury
All planets in almost circular (elliptical)
orbits around the sun, in approx. the same
plane (ecliptic).
Sense of revolution: counter-clockwise
Sense of rotation: counter-clockwise (with exception of Venus, Uranus, and
Pluto)
Orbits generally inclined by no more than 3.4o
Exceptions:
Mercury (7o)
Pluto (17.2o)
(Distances and times reproduced to scale)
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Orbits
Revolution – the movement of an object around another object
Orbit – the path taken by a revolving object
Celestial objects have elliptical orbits
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Elliptical Orbit A circle has one central point, called a
focus. Ellipses have two points, called foci.
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Eccentricity
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Calculate the eccentricity of the ellipse below:
Formula: eccentricity = distance between foci length of major axis
length of major axis
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Regents Question
Which object is located at one foci of the elliptical orbit of Mars?
(1)the Sun (3)Earth (2)Betelgeuse (4)Jupiter
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Regents Answer
(1)the Sun
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Regents Question The bar graph below shows one planetary characteristic,
identified as X, plotted for the planets of our solar system.
Which characteristic of the planets in our solar system is represented by X?
(1)mass (3)eccentricity of orbit (2)density (4)period of rotation
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Regents Answer
(3)eccentricity of orbit
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Regents Question
Which planet has the least distance between the two foci of its elliptical orbit?
(1)Venus (3)Mars (2)Earth (4)Jupiter
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Regents Answer
(1)Venus
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Laws of Planetary Motion Devised by German
astronomerJohannes Kepler: 1. The planets move in elliptical orbits,
with the Sun at one focus 2. The line joining the Sun and a planet
sweeps equal areas in equal intervals of time
3. The square of the time of revolution (T²) is proportional to the planet’s mean distance from the Sun (R³)
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Kepler’s First Law
• Planets move around sun in elliptical orbits. • Sun is at one focus point. • Flatness called eccentricity • Formula in ESRT.
Focus points
Major axis
Eccentricity =
Distance between foci Length of major axis
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Kepler’s Second Law
Area of orange section is equal.
Distance along orbit is not the same. But the time covered is equal. eccentricity website
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Kepler's Third Law
Not drawn to scale.
Earth – 150 mill. Km, 365 days
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Orbital Energy
Gravitation – the force of attraction between 2 objects
Inertia – the tendency of an object in motion to continue in motion along a straight path
The interaction of gravity and inertia keep planets in orbit
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Energy Transfer
Energy is transferred between potential and kinetic as a planet orbits the Sun.
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Orbital Velocity
The Earth’s orbital velocity is highest when kinetic energy is the highest.
This occurs when the Earth is nearest to the Sun in its orbit.
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When furthest from Sun
When closest to Sun
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eccentricity website
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Which planet has the least perfectly circular orbit?
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Which planet has the most perfectly circular orbit?