The Universe8th 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 AstronomyOptical 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 no 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 oval-like

-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.