The Universe

8

th

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 1 st 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 5 o .

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 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.