Exploring Space

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Exploring Space
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Looking from Earth

• Telescopes are used to see objects that are far
  away.
• The largest telescopes are up to 300m wide
• There are 3 types
• Reflecting
• Refracting
• Radio

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Optical Telescopes

• Refracting and reflecting telescopes are both
  types of optical telescopes
• They use lenses and mirrors to produce magnified
  images

• Professional astronomers house the telescopes in
  observatories
• The Hubble Space Telescope was launched in 1990
  in order to get better quality picture of the
  universe.

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Radio Telescopes

• All stars radiate energy throughout the
  electromagnetic spectrum
• Light, x-rays, radio waves, microwaves, etc
• Radio telescopes study the radio waves
• A computer takes data about the radio waves and
  makes a map
• The largest radio telescope in the world is 300m
  wide

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Satellites

• Space exploration began in 1957 with the Soviet
  satellite Sputnik I
• Today thousands of artificial satellites orbit
  the Earth
• Space probes carry instruments to gather
  information and send it back to Earth.
• There have been several important probes sent out
  by the National Aeronautics and Space
  Administration (NASA)

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Mariner 2 Viking 1

• Launched in August 1962
• First successful planetary probe
• Verified high temperatures in Venus atmosphere

• Launched August 1975
• Mapped Martian surface
• Searched for life on the surface

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Pioneer 10

• Launched March 1972
• First probe to encounter Jupiter
• Sent back photographs and data

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Voyager

• 2 probes were launched in 1977
• Voyager 1
• Flew past Jupiter Saturn
• Voyager 2
• Flew past Jupiter, Saturn, Uranus, and Neptune
• Sent back information from all the planets it
  visited

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Galileo

• Launched in 1989
• Reached Jupiter in 1995
• Sent a probe in to the atmosphere
• Returned data on composition, temperature, and
  pressure
• Also studied Jupiters moons, rings, and
  magnetic fields

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Race to the moon

• In 1961, President John F. Kennedy called for the
  US to put a person on the moon and began the
  space race.
• The race to the moon was undertaken in 3 projects
• Project Mercury
• Project Gemini
• Project Apollo

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Project Mercury

• Goal To orbit a piloted spacecraft around the
  Earth and bring it back safely
• Significant Events
• May 5, 1961 Alan Sheppard became the first US
  citizen in space
• 1962 John Glenn became the first US citizen to
  orbit the Earth

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Project Gemini

• 2 astronauts in the same Gemini spacecraft
  orbited the Earth
• One team met and connected with another space
  craft in orbit.
• Ranger Surveyor Proved we could land on the
  moon

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Project Apollo

• Goal to reach the moon
• July 20, 1969 Apollo 11 landed on the lunar
  surface
• Neil Armstrong became the first man to set foot
  on the moon.
• One small step for man, one giant leap for
  mankind.

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Beyond our Solar System

• Characteristics of Stars
• Color
• Temperature
• Brightness
• Mass

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Color and Temperature

• Color tells us temperature of a star
• Very hot stars temperatures above 30,000 K are
  blue
• Stars between 5,000 K and 6,000 K appear Yellow
• Cooler stars under 5,000 K appear Red

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Stellar Mass

• Binary stars- 2 stars pulled together in orbit by
  the force of gravity
• They orbit each other around a center of mass
• If the center of mass is known than we can
  calculate mass of the stars
• Example- if the stars have equal mass the center
  of mass is exactly halfway between them

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Measuring Star Distance

• Shifting of a nearby star due to the orbital
  motion of Earth
• How is it done?
• Photograph a nearby star
• Photograph the same star 6 months later
• Calculate distance from star by the amount and
  angle of the shift

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Light Years

• Distances to stars are so large that we need a
  special unit to measure them
• 1 Light Year is the distance light travels in one
  years time
• 9.5 X 1012 Kilometers
• Or 9.5 trillion Kilometers
• Proxima Centauri is 4.3 light years away
• (9.5 trillion kilometers X 4.3)

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Stellar Brightness

• Magnitude measure of stars brightness
• Apparent magnitude how bright a star appears
  from Earth
• Factors that effect apparent magnitude
• How big it is
• How hot it is
• How far away it is

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Absolute magnitude

• Actual brightness of a star
• 2 stars with the same absolute magnitude may not
  necessarily have the same apparent magnitude

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Stellar Evolution

• Stars start off as dark clouds of 92 hydrogen,
  7 helium, lt 1 heavier elements
• Gravity squeezes matter inward and the interior
  heats up
• Protostar- early phase where star is heating up
  (spans 1 million years)

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Star Birth

• When the core of the Protostar reaches 10 million
  K, pressure is so great that nuclear fusion
  occurs- a star is born
• Heat from fusion of hydrogen is released
• When balance is maintained from inward pressure
  (gravity) and outward pressure (heat) the
  Main-Sequence stage is reached

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Main-Sequence Stage

• Hydrogen fusion occurs for a few billion years
• Stars age at different rates
• Blue stars- burn so hot they deplete hydrogen
  quickly (few million years)
• Red/Yellow stars- burn cooler so their hydrogen
  lasts longer (our sun 10 billion years)

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Red Giant Stage

• Hydrogen depleted in core leaving a helium core
• Core loses outward heat pressure and begins to
  collapse
• As core contracts it grows hotter by converting
  gravitational energy into heat energy- this
  energy starts to fuse hydrogen in outer layers

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Red Giant Stage

• The heat energy expands stars outer layer
  resulting in a giant body hundreds to thousands
  of times larger than its main sequence size
• Previous events are all well documented- what
  happens next is based on theory

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Burnout and Death

• Stars eventually run out of fuel and collapse due
  to gravity
• Death of different size stars
• Low-mass stars
• Remain in main-sequence until fuel runs out and
  than collapse into white dwarf
• White dwarf- extremely dense remains of stars
• Black dwarf- a white dwarf that has cooled down

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• Medium mass stars
• Reach giant phase fusing hydrogen and helium
• Then collapse from red giants to white dwarfs
• White dwarfs are extremely dense remains of stars
• Cast the outer layer creating an expanding cloud
  of red gas (called planetary nebula)

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• Massive stars
• Have short life spans and die out with a
  brilliant explosion (supernova)
• During a supernova the outer layer of the star is
  ejected while the core collapses
• Star becomes a million times brighter than the
  prenova phase
• If one of the nearest stars to Earth went into
  supernova it would be brighter than our sun

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Black Holes

• During a supernova remnants of stars 3X the size
  of the sun collapse into small dense objects
  (Black Holes)
• These black holes have gravitational energy so
  strong that even light cannot escape their
  surface
• How do we find them?
• Look for the heat emitted as matter is being
  pulled in

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Galaxies

• Group of stars, dust, and gases held together by
  gravity
• Billions of stars in our galaxy- The Milky Way
• 100,000 light years across
• Spiral galaxy

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Types of Galaxies

• Spiral
• Great concentration of stars near the center
• Large galaxies containing billions of stars
• Elliptical
• Round to oval in shape
• Smaller galaxies
• Irregular
• Composed of mostly young stars

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Hubbles Law

• Red shifts- Hubble observed that most galaxies
  have red shifts
• Red shifts show that light waves are being
  stretched
• This means that Earth and the source of the light
  waves are being moved away from each other
• Greater red shifts mean faster speeds

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Hubbles Law

• Galaxies further away have greater red shifts and
  therefore are moving faster
• The Universe is Expanding!!!!
• This discovery led to the Big Bang Theory
• At one time the entire universe was confined to a
  dense, hot, supermassive ball. 13.7 billion years
  ago a violent explosion occurred hurling this
  material in all directions
• Evidence- 1) red shifts 2) cosmic radiation
  produced during the explosion

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What is the fate of our Universe?

• Expansion lasting forever as stars die out and
  the universe is filled with dense black dwarfs
  and black holes
• The Big Crunch- will gravity pull everything back
  into a high density, high energy mass as it was
  before the big bang?