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April 19, 2023 1
AstronomyAstronomyThe Universe The Universe
StarsStarsOur Solar SystemOur Solar System
OrbitsOrbitsGravityGravity
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The Size of the The Size of the UniverseUniverse
Distance in space is often Distance in space is often measured in measured in light yearslight years
One light year is the One light year is the distancedistance that that light travels in one Earth yearlight travels in one Earth year Our moon is 1 1/2 light second awayOur moon is 1 1/2 light second away Our sun is 8 light minutes awayOur sun is 8 light minutes away Our closest star (besides the sun) is 4 Our closest star (besides the sun) is 4
light years awaylight years away The universe is thought to be 25 The universe is thought to be 25
billion light years across!billion light years across!
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Origin of the UniverseOrigin of the Universe
Big bangBig bang Approximately 15 billion years agoApproximately 15 billion years ago Started from a single point and has Started from a single point and has
been spreading outward ever sincebeen spreading outward ever since
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Raisin bread analogy of an Raisin bread analogy of an expanding universeexpanding universe
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Organization of the Organization of the UniverseUniverse
Planet (Earth)
Solar System
Galaxy (ex. Milky Way)
Galaxy Cluster
Universe
Star (Sun)
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GalaxiesGalaxies A huge cluster of stars and other A huge cluster of stars and other
matter is called a matter is called a GalaxyGalaxy MoveMove
Rotate in place (spin)Rotate in place (spin) Move away from the center of the Move away from the center of the
universeuniverse Have different shapesHave different shapes
Spiral, like the Milky WaySpiral, like the Milky Way GlobularGlobular RingRing
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Expansion Evidence for Big Expansion Evidence for Big BangBang
Electromagnetic Energy - Type of Electromagnetic Energy - Type of energy given off in the form of energy given off in the form of transverse waves transverse waves
Different types of electromagnetic Different types of electromagnetic energy are distinguished by their energy are distinguished by their different wavelengthsdifferent wavelengths
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Page 14 of the ESRTPage 14 of the ESRT
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Electromagnetic Spectrum Electromagnetic Spectrum – humans can only see one – humans can only see one part of spectrum – visible part of spectrum – visible
lightlight
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Expansion Evidence Expansion Evidence
Most stars are made of Hydrogen & Most stars are made of Hydrogen & Helium gas. Helium gas.
Elements that emit specific Elements that emit specific wavelengths within the wavelengths within the electromagnetic spectrum.electromagnetic spectrum.
The spectral line pattern can be used The spectral line pattern can be used to identify the star rather like a to identify the star rather like a fingerprint or bar code. fingerprint or bar code.
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Red ShiftRed Shift – – Blue ShiftBlue Shift In 1929, Edwin Hubble observed In 1929, Edwin Hubble observed
that spectral lines emitted by stars that spectral lines emitted by stars in distant galaxies were in distant galaxies were considerably considerably Red shifted.Red shifted.
If a galaxy or star were moving If a galaxy or star were moving toward the earth, the spectral lines toward the earth, the spectral lines would show a would show a blue shift.blue shift.
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Shifting of Wavelengths is Shifting of Wavelengths is called the Doppler Effectcalled the Doppler Effect
• Change in the Change in the wavelength of light wavelength of light emitted by an object due emitted by an object due to its motion to its motion
• Movement toward Movement toward “squeezes” the wavelength“squeezes” the wavelength
• Shorter wavelengthShorter wavelength• Light shifted toward the Light shifted toward the
blue end of the spectrum blue end of the spectrum
• Movement away stretches Movement away stretches the wavelength the wavelength
• Longer wavelengthLonger wavelength• Light shifted toward the Light shifted toward the
red end of spectrumred end of spectrum
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RED SHIFT – RED SHIFT – BLUE BLUE SHIFTSHIFT
The greater the degree of shift of the The greater the degree of shift of the spectral lines, the faster the object is moving spectral lines, the faster the object is moving awayaway
The star light DOES NOT appear red or blue The star light DOES NOT appear red or blue (it still appears as white light from the star) (it still appears as white light from the star)
The “bar code” for each element either shifts The “bar code” for each element either shifts to the shorter wavelength blue end of the to the shorter wavelength blue end of the spectrum or to the longer wavelength red spectrum or to the longer wavelength red end of the spectrumend of the spectrum
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What is the best inference that can be made concerning the movements of Galaxies A, B, and C?
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Hubble Telescope and Deep Hubble Telescope and Deep SpaceSpace
The Hubble Telescope was pointed The Hubble Telescope was pointed at an area of “nothing”at an area of “nothing”
The next slide is the image Hubble The next slide is the image Hubble captured.captured.
Each bright spot is a galaxy, similar Each bright spot is a galaxy, similar to our own Milky Wayto our own Milky Way
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Hubble Deep Space GalaxiesHubble Deep Space Galaxies
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Inferences about our Inferences about our GalaxyGalaxy
Large (as galaxies go): 100,000 ly Large (as galaxies go): 100,000 ly acrossacross
Contains several hundred billion Contains several hundred billion starsstars
The Milky Way rotates once every The Milky Way rotates once every 220 million years220 million years That means we are moving at 250 km That means we are moving at 250 km
per second!!per second!!
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The Milky Way: our The Milky Way: our galaxygalaxy
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Our solar system is part of Our solar system is part of the spiral Milky Way Galaxythe spiral Milky Way Galaxy
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Edge-on view of the Edge-on view of the Milk Way GalaxyMilk Way Galaxy
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April 19, 2023 25Elliptical GalaxyElliptical Galaxy
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Spiral galaxy in the Spiral galaxy in the constellation Andromedaconstellation Andromeda
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Barred Spiral
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Our Solar System in the Our Solar System in the Milky Way:Milky Way:
Is located in an arm on the outer Is located in an arm on the outer edge of the Milky Wayedge of the Milky Way
We face in to the center of the We face in to the center of the galaxy in the wintergalaxy in the winter This is why the Milky Way is brighter This is why the Milky Way is brighter
in the winter timein the winter time
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Stars Stars Fueled by nuclear fusionFueled by nuclear fusion
When atoms are compressed so hard When atoms are compressed so hard they “fuse”they “fuse”
Creates a tremendous amount of energyCreates a tremendous amount of energy Our closest star is the SunOur closest star is the Sun
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StarsStars Stars are born, live and dieStars are born, live and die Classified based on size and Classified based on size and
temperaturetemperature What they become in death can be What they become in death can be
determined by the Hertzsprung-determined by the Hertzsprung-Russell Diagram (H-R Diagram)Russell Diagram (H-R Diagram)
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Which groups of stars are the BRIGHTEST?
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Which group of stars is the HOTTEST?
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Which groups of stars are the SMALLEST and DIMMEST?
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Our SunOur Sun A medium sized starA medium sized star Makes up 99.86% of the Sloar Makes up 99.86% of the Sloar
System’s mass!System’s mass! Contains sunspotsContains sunspots
Storms within the hot gasStorms within the hot gas Appear as black spots that move across the Appear as black spots that move across the
surfacesurface Are produced in cyclesAre produced in cycles
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SatellitesSatellites Any object that orbits another Any object that orbits another
object in space is known as a object in space is known as a satellitesatellite Planets are natural satellites of Planets are natural satellites of
their stars their stars Moons are natural satellites of their Moons are natural satellites of their
planetsplanets We also have artificial satellites We also have artificial satellites
which orbit Earthwhich orbit Earth
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Our Solar SystemOur Solar System The Sun is near the center of the The Sun is near the center of the
Solar SystemSolar System Satellites in the Solar System:Satellites in the Solar System:
Rocky planetsRocky planets Like your home planetLike your home planet
Gas giantsGas giants Solid core surrounded by gasSolid core surrounded by gas
Other stuffOther stuff Asteroids, meteors and cometsAsteroids, meteors and comets
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The Planets: Two kindsThe Planets: Two kinds
Rocky Rocky (Terrestrial)(Terrestrial) MercuryMercury VenusVenus EarthEarth MarsMars PlutoPluto
Gas GiantsGas Giants JupiterJupiter SaturnSaturn UranusUranus NeptuneNeptune
Saturn would Saturn would float if you float if you could put it in could put it in water!water!
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The Big “E”The Big “E” Earth is uniqueEarth is unique
Due to abundant liquid waterDue to abundant liquid water Means life as we know it!Means life as we know it!
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Home!Home!
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Other Natural SatellitesOther Natural Satellites
AsteroidsAsteroids Chunks of rock and metal that circle Chunks of rock and metal that circle
the sun Range in size from hundreds the sun Range in size from hundreds of km to mmof km to mm
Most are in a belt between Mars and Most are in a belt between Mars and JupiterJupiter
Rarely cross Earth’s orbitRarely cross Earth’s orbit May have caused the extinction of May have caused the extinction of
dinosaursdinosaurs
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CometsComets ““Dirty snowballs” from outside the solar Dirty snowballs” from outside the solar
systemsystem Probably provided young Earth’s waterProbably provided young Earth’s water ““Tail” created by vaporization when they Tail” created by vaporization when they
approach the Sunapproach the Sun Examples: Examples:
Halley’s – 76 year orbit (will be back in 2061)Halley’s – 76 year orbit (will be back in 2061) Hale-Bopp – was near in 1997 (will be back Hale-Bopp – was near in 1997 (will be back
in ???)in ???)
Other Natural SatellitesOther Natural Satellites
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Comet Hale-BoppComet Hale-Bopp
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MeteorsMeteors Small particles pulled into Small particles pulled into
Atmosphere by Earth’s gravityAtmosphere by Earth’s gravity Most burn up in the atmosphereMost burn up in the atmosphere
Shooting starsShooting stars If they reach the Earth’s surface are If they reach the Earth’s surface are
called meteoritescalled meteorites Evidence of meteors: Evidence of meteors:
Most is eroded awayMost is eroded away Meteor Crater in Winslow AZMeteor Crater in Winslow AZ
Other Natural SatellitesOther Natural Satellites
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Terrestrial Planets – Earth Terrestrial Planets – Earth largest solid, smaller, largest solid, smaller,
denserdenser
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Earth compared to Jovian Earth compared to Jovian PlanetsPlanets
gaseous, large, low densitygaseous, large, low density
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All planets compared to Our All planets compared to Our SunSun
No longer considered a planet
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Kepler’s Three Laws of Kepler’s Three Laws of Planetary MotionsPlanetary Motions
1.1. Planets’ orbits’ are elliptical in Planets’ orbits’ are elliptical in shapeshape
2.2. A planet will move through equal A planet will move through equal area of space in an equal amount of area of space in an equal amount of timetime
3.3. The farther a planet is from the The farther a planet is from the focus, the longer the period of focus, the longer the period of revolutionrevolution
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Kepler’s First LawKepler’s First Law
The orbits The orbits of planets of planets around around stars is stars is ellipticalelliptical
circle ellipse
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Geometry of OrbitsGeometry of Orbits
The orbits of The orbits of planets around planets around their star are their star are elliptical with elliptical with the star at one the star at one focus and the focus and the planet’s planet’s average mass average mass at the other at the other focus focus
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Geometry of OrbitsGeometry of Orbits
The major axis is defined by a line that The major axis is defined by a line that passes through the two foci (plural of focus)passes through the two foci (plural of focus)
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Geometry of OrbitsGeometry of Orbits The word The word
eccentricity is eccentricity is used to describe used to describe how “out of how “out of round” an orbit isround” an orbit is
Eccentricity can Eccentricity can be defined be defined numerically numerically
No units are used No units are used in describing in describing eccentricityeccentricity
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SHAPE OF ELLIPSESSHAPE OF ELLIPSES
Eccentricity = 0 Eccentricity = 0 circle circle
Eccentricity = 0.5Eccentricity = 0.5
Eccentricity = 1 Eccentricity = 1 line line
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Kepler’s Three Empirical Kepler’s Three Empirical Laws of Planetary MotionLaws of Planetary Motion1. The orbital paths of the planets are elliptical, with the Sun at one focus
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Kepler’s Three Empirical Kepler’s Three Empirical Laws of Planetary MotionLaws of Planetary Motion
2. An imaginary line connecting the Sun to any planet sweeps out equal areas in equal time..
Area 2
Area 1
TO THE HUMAN EYE, MOST TO THE HUMAN EYE, MOST ORBITS OF PLANETS LOOK LIKE ORBITS OF PLANETS LOOK LIKE CIRCLESCIRCLES
SLIGHTLY ELLIPTICAL SHAPE OF SLIGHTLY ELLIPTICAL SHAPE OF EARTH’S ORBIT CAUSES THE EARTH’S ORBIT CAUSES THE PLANET TO VARY THE DISTANCE PLANET TO VARY THE DISTANCE TO THE SUN DURING REVOLUTION TO THE SUN DURING REVOLUTION
147 million kms.
152 million kms.
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This is the best website for 1st and 2nd laws of Keplerhttps://solarsystem.colorado.edu/home/lowRes.html
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Geometry of OrbitsGeometry of Orbits
The formula for finding eccentricity is:The formula for finding eccentricity is:
Eccentricity =Distance between the foci
Length of the major axis
This formula is found in your ESRTs
***Units must be the same in the numerator and denominator, then the units cancel and eccentricity is expressed without units.
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The distance between foci of The distance between foci of planet beta’s orbit is 3000 km. The planet beta’s orbit is 3000 km. The length of it’s major axis is 600,000 length of it’s major axis is 600,000 km. What is the eccentricity of km. What is the eccentricity of Beta’s orbit?Beta’s orbit?
Eccentricity ExampleEccentricity Example
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Eccentricity ExampleEccentricity Example A comet has a major axis with A comet has a major axis with
length 12,000,000 km and foci that length 12,000,000 km and foci that are 24,000 km apart. What is the are 24,000 km apart. What is the eccentricity of the comet’s orbit?eccentricity of the comet’s orbit?
Which has a more eccentric orbit, Which has a more eccentric orbit, the comet or Beta? the comet or Beta?
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The Force of GravityThe Force of Gravity Earth’s orbit around the sun has an Earth’s orbit around the sun has an
eccentricity of 0.017 (close to zero)eccentricity of 0.017 (close to zero) Therefore the distance between the Therefore the distance between the
sun and Earth changes very little sun and Earth changes very little throughout the yearthroughout the year
What is the difference in distance What is the difference in distance between the Earth’s nearest between the Earth’s nearest approach and farthest distance approach and farthest distance from the sun?from the sun?
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The speed of a planet varies with its distance from the The speed of a planet varies with its distance from the sunsun
The closer to the sun, the faster the planet travels in The closer to the sun, the faster the planet travels in its revolution around the sunits revolution around the sun
Kepler’s Second Law: Kepler’s Second Law: The Force of GravityThe Force of Gravity
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Equal Area, Equal TimeEqual Area, Equal Time
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Kepler’s Third Law in our Kepler’s Third Law in our Solar SystemSolar System
Use your ESRT to complete the chart below:Use your ESRT to complete the chart below:
PlanetPlanet Distance from Distance from SunSun
Period of Period of RevolutionRevolution
MercuryMercury
EarthEarth
MarsMars
SaturnSaturn
UranusUranus
PlutoPluto
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OrbitOrbits in s in our our
Solar Solar SysteSyste
mm
