Transcript The Universe - Lancaster High School

The Universe
8th Grade Science
Modern Calendar
-Year – time for Earth to orbit once around
Sun.
-Month – time for moon to orbit once around
Earth.
-Day – time for Earth to rotate once on axis.
Early Astronomers
Ptolemy
-Greek
-140 CE
-Earth-centered solar
system
-Incorrect, but believed
for over 1500 years
Early Astronomers
Copernicus
-Polish
-1543
-Sun-centered solar
system
-Afraid to publish theory
-Copernican Revolution
Early Astronomers
Brahe
-Danish
-Late 1500’s
-Most detailed observations
so far
-Earth-centered Solar
system – but different…
-Sun & moon orbit Earth
-Rest of planets orbit Sun
Early Astronomers
Kepler
-German
-Brahe’s assistant
-Disagreed with Brahe’s idea
of solar system, but
realized value of his data
-Sun-centered solar system
-Planets – elliptical orbits
-3 laws of planetary motion
Early Astronomers
Galileo
-Italian
-1609
-One of the 1st people to use
telescope
-Discoveries:
-craters & mts. on Luna
-4 moons of Jupiter
-sunspots on Sun
-phases of Venus
-House arrest
Early Astronomers
Newton
-English
-early 1700’s
-Apple myth
-Gravity
-Explained why
planets orbit Sun
-Laws of Motion
Modern Astronomy
Hubble
-American
-1920’s
-Galaxies beyond
Milky Way
-Universe expanding
-Space telescope
named in his honor
Modern Astronomy
Chandrasekhar
-Indian-born American
-1930’s-40’s
-structure & evolution
of stars
-Chandrasekhar limit
-White dwarfs
-Nobel Prize in Physics
Modern Astronomy
Sagan
-American
-1960’s-70’s
-lead search for “et” (SETI)
-Contact
-missions to Mars & other
outer planets
-coined term “nuclear
winter”
Modern Astronomy
Hawking
-British
-1980’s-current
-black holes emit
radiation
-universe infinite, theory
of everything
-ALS
Electromagnetic Spectrum
-Wavelengths of electromagnetic radiation
-James Clerk Maxwell, Scottish (whoo-hoo),1852
Tools of Astronomy
Optical telescopes
-gather & focus VISIBLE
LIGHT
-reflecting (lenses)vs.
refracting (curved mirrors)
-on Earth – dirty windshield
-in Space – MUCH better
-Hubble ST
Tools of Astronomy
Nonoptical Telescopes
-Radio telescopes–radio
waves (VLA)
-UV Telescopes
-X-ray Telescopes
-most in space due to
atmosphere blocking.
-all very powerful!
Sun in Different Wavelengths
Constellations
-Regions of sky with recognizable star patterns
-Navigation & track of time
-Different cultures = different names/stories
Measuring Distance in Space
-Astronomical Unit (AU) – distance between Earth & Sun
(1AU)
-about 150 million km (93 million miles)
-distance in solar system only!
-Light-year- distance light travels in 1 year.
-about 9.46 trillion kilometers!
-distance in galaxies or between
-Parsec – 3.26 light years
-about the distance to the closest star.
Doppler Effect
-Occurs with sound & light waves
-Sound – train passing by
-Light
-Redshift – object moving away, light looks redder
-Blueshift – object moving toward, light looks bluer
Moons
-Satellite – natural or artificial – orbit around larger
bodies.
-moon- natural satellite.
-All planets (except Mercury & Venus) have moons.
-Luna – Earth’s moon.
Formation of Luna
-Composition similar to Earth’s mantle.
-moon rocks from Apollo mission analyzed.
~4.6 bya, Mars-sized object hit Earth.
-blasted part of mantle into orbit.
-debris revolved, joined to form Luna.
-Figure 2, page 111
Earth & Luna
Moon Phases
-Moon appears different due to changing positions.
-waxing – sunlit area we see is getting bigger.
-waning – sunlit area we see is getting smaller.
-We always see same side of moon.
-moon’s period of rotation=its period of revolution.
-Figure 3, page 112
Solar Eclipse
-Moon comes b/t Earth & Sun.
-shadow of moon falls on part of Earth.
-pg. 113
-Annular – moon farther from Earth.
-disk of moon doesn’t completely cover Sun.
-Total – moon closer to Earth.
-disk of moon completely covers Sun.
Lunar Eclipse
-Earth comes b/t Sun & moon.
-shadow of Earth falls on moon.
-pg. 114
-Why don’t we see one every month?
-moon’s orbit tilted about 5o.
Comets
-Ice, dust, rock particles
-”dirty snowballs”
-Formed in outer solar system.
-”leftovers” from formation of solar system.
-Oort Cloud – past Pluto
-Kuiper Belt – past Neptune
Asteroids
-Rocky objects – orbit Sun
-few km – more than 900 km!
-Most orbit in asteroid belt
-between Mars & Jupiter
-Larger than 10 km in diameter = catastrophic
global effects.
Meteoroids, ors, ites
-Small, rocky bodies – orbit Sun.
-probably pieces of asteroids.
-OIDS – In Space
-ORS – Bright streak as it enters Earth’s
atmosphere.
-ITES – If it strikes the ground.
Impacts
-Planets/Moons with atmosphere = not as
many impacts……..why????
-atmosphere slows down/burns up
meteoroids.
-Why are there not many impact craters on
Earth?
-weathering, erosion, plate tectonics
-
Earth Impacts
-Impact - global catastrophe – every few
hundred thousand years.
-Impact – natural disaster – every few
thousand years.
-Meteor Crater, Arizona
-1 mile across
-550 ft. deep
-formed 50,000 yrs. ago
Torino Scale
-Rates hazard level of space objects moving
toward Earth.
-numbered 0 – 10
-0 being no worries – 10 being worst case
-also color coded
-Developed by NASA
http://neo.jpl.nasa.gov/torino_scale.html
Journey Out of Our Solar System
Stars
-Composition – gases, mainly H & He.
-Star’s Color tells us Temperature:
-blue = hotter
-red = cooler
-Classified by how hot they are.
-Orion Constellation
-Betelgeuse:
Red Supergiant
-Rigel:
Blue Supergiant
Classifying Stars
-Oh, Be A Fine Girl (Guy), Kiss Me!
-pg. 35 – what does this mean???
-Which class stars are hottest?
-Which class stars are coolest?
“Life Cycle” of Stars
-A Star is Born:
-Stellar nursery(nebula) - huge cloud of gas
& dust..
-Material compresses & heats up…
-Begins to glow with radiation…
-Temps in core reach 18 billion degrees F...
-Begins nuclear fusion!!!
Rosette Nebula
Adulthood – Main Sequence
-Longest lasting stage
-Stable existence – no real turmoil
-Core continues nuclear fusion
-Our Sun
Main
Sequence
Star
Crisis – Old Age
-How long a star live depends on its mass
-smaller stars burn fuel less quickly = longer life.
-bigger stars burn fuel more rapidly = shorter
life.
-All eventually run out & move along the cycle…
Death Begins…
-Outer layers “grow” & turn reddish in color
-can get as large as the orbits of Mars or Jupiter
-Called red giants or red supergiants
-Remainder of death can go one of 3 ways…
-Betelgeuse
3 Directions of Death…
1. Release of Outer layers – Sun
2. Nova – Stars bigger than Sun – explosion
3. Supernova – Most massive stars – Chuck
Norris of explosions.
-can be as bright as an entire galaxy
In the Graveyard…
1. White dwarf – small, hot leftover center
-stars the size of Sun or smaller
2. Neutron star – collapses under gravity – all
particles are neutrons – extremely dense
-stars 5-20 times mass of Sun
-Pulsar – spinning Neutron star
3. Black Hole – gravity so immense that nothing
can escape – not even light
-stars 20 times or more massive than Sun
Galaxies
-Large groups of stars, gas & dust.
-variety of shapes & sizes
-largest contain more than a trillion stars!
-billions of galaxies in known universe
-Classified by shape.
Spiral Galaxies
-Central bulge & spiral arms
-arms made of gas, dust & newer stars
-Barred spirals – bar-shaped bulge
-Milky Way, Andromeda
-Sagittarius arm, Orion spur
-Milky
Way
-Arms of
Milky Way
-Side view
Elliptical Galaxies
-Massive blobs of stars – look sphere or ovallike
-VERY bright centers
-very little gas & dust
-Contain mostly OLD stars
Irregular Galaxies
-”Leftovers” – don’t fit into the other groups
-shape sometimes distorted by nearby large
galaxies
Gas Clouds
-Nebula – cloud of gas & dust
-Found mostly in spiral galaxies
-some reflect starlight, some absorb
Part of the Eagle Nebula
Horse head Nebula
Cat’s Eye Nebula
Star Clusters
-Globular Cluster – older stars.
-may contain up to a million stars
-located in halo that surrounds galaxies
-Open Cluster – closely grouped, younger
stars
-contain many bright, blue stars
-a few hundred to a few thousand stars
-located in spiral disk
-Globular
Cluster
Omega
Centauri
Open Cluster - The Pleiades
Quasars
-Star-like sources of light – extremely far away
-most powerful energy sources in universe
-may be caused by super massive black
holes in cores of some galaxies.