Astronomy

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Astronomy
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Universe

• All matter and energy, including the earth, the
  galaxies, and the contents of intergalactic
  space, regarded as a whole.

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Galaxy

• A component of our universe made up of gas and a
  large number (usually more than a million) of
  stars held together by gravity. When capitalized,
  Galaxy refers to our own Milky Way Galaxy.
• Three types of galaxies
• Elliptical
• Spiral
• Irregular

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Elliptical Galaxy

• Have a round Oval Shape

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Spiral Galaxy

• Pinwheel Shape

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Irregulars Galaxy

• No predictable shape

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Compare Contrast ChartGive out handout

• Spiral
• Are huge
• Contain stars, gas, dust
• Are held together by gravity
• A halo is present

• Elliptical
• Are huge
• Contain stars, gas, dust
• Are held together by gravity
• A halo is present

• Irregular
• Are huge
• Contain stars, gas, dust
• Are held together by gravity
• A halo is present

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Compare Contrast Chart

• Spiral
• Round to oval shape
• Bulge, but no disk
• Small amount of cool gas dust
• Mainly old stars

• Elliptical
• Pinwheel shape
• Bulge a thin disk
• Rich in gas dust
• Young old stars

• Irregular
• No predictable shape
• May show signs of a disk /or a bulge
• Usually rich in gas dust
• Young old stars

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Bulge
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Milky Way
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Our place in the universe. This figure
illustrates our cosmic address. The Earth is one
of the nine planets in our solar systems, our
solar system is one among 200 billion star
systems in the Milky Way Galaxy the Milky Way is
one of the two largest of about 30 galaxies
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Milky Way

• Ask an Astrophysicist 
• Size The disk of the Milky Way galaxy is about
  100,000 light years in diameter (one light year
  is about 9.5 x 1015 meters), but only about 1000
  light years thick.
• Our Galaxy contains about 200 billion stars. Most
  of the stars are located in the disk of our
  galaxy, which is the site of most of the star
  formation because it contains lots of gas and
  dust.

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Milky Way w/ location of our Solar System
Solar System's orbit within Milky Way Galaxy. The
sun is ONE of the estimated 200 billion stars in
this galaxy.
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Solar System

• Our solar system consists of
• the sun, eight planets, moons, many dwarf planets
  (or plutoids), an asteroid belt, comets, meteors,
  and others.
• The sun is the center of our solar system the
  planets, their moons, a belt of asteroids,
  comets, and other rocks and gas orbit the sun.

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Steps of Solar System Formation

• A Globule of GasOur solar system formed about
• 4.6 billion years ago, from an enormous cloud of
  dust and gas, a nebula.
• The Sun, like other stars, was formed in a
  nebula, an interstellar cloud of dust and gas
  (mostly hydrogen).
• These stellar nurseries are abundant in the arms
  of spiral galaxies (like our galaxy, the Milky
  Way).

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Sun

• Later, the Sun stabilizes and becomes a yellow
  dwarf, a main sequence star which will remain in
  this state for about 10 billion years. After
  that, the hydrogen fuel is depleted and the Sun
  begins to die.

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Inner vs. Outer Planets

• Inner- Terrestrial (Land)
• Mercury, Venus, Earth, Mars
• Closer to the Sun
• Are rocky have craters
• Atmosphere Mercury- N/A other planets have CO2
  in common. Earth only one w/O2
• http//lasp.colorado.edu/education/outerplanets/so
  lsys_planets.php

• Outer- Gas Giants
• Jupiter, Saturn, Uranus, Neptune, Pluto (a
  dwarf planet)
• Farther from the Sun (cooler)
• Farther apart from one another
• Are made of gas
• Atmosphere mostly Helium Hydrogen

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Gravitational Forces- Planets

• Jupiter Strongest gravitational attraction
• Although Saturn, Uranus, and Neptune are also
  very massive planets, their gravitational forces
  are about the same as Earth.
• This is because the gravitational force a planet
  exerts upon an object at the planet's surface is
  proportional to its mass and the planet's radius
  squared.

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Inner vs. Outer Planets

• Inner- Terrestrial
• Mercury, Venus, Earth, Mars
• Few moons
• Mercury Venus no moons

• Outer- Gas Giants
• Jupiter, Saturn, Uranus, Neptune, Pluto (a
  dwarf planet)
• Many moons
• Jovian Planets collapsed, smaller particles in
  the surrounding disk formed into some of the
  moons that now orbit the individual outer
  planets. This makes sense, since the outer
  planets all have many moons and rings.

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Inner vs. Outer Planets

• Inner- Terrestrial
• Mercury, Venus, Earth, Mars
• No rings

• Outer- Gas Giants
• Jupiter, Saturn, Uranus, Neptune, Pluto (a
  dwarf planet)
• Rings
• The rings are thin discs of dust and rocks
  possibly caused by moons being broken up or not
  being completely formed while orbiting the
  planet.

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Inner Planets
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Outer Planets
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Outer Planets
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Asteroid Belt

• An asteroid is a bit of rock.
• "left overs" after the Sun
• and all the planets were
• formed.
• Most of the asteroids in our solar system can be
  found orbiting the Sun between the orbits of Mars
  and Jupiter.
• This area is sometimes called the "asteroid
  belt.
• Think about it this way the asteroid belt is a
  big highway in a circle around the Sun. Think
  about the asteroids as cars on the highway.

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Asteroid Belt

• The asteroid belt lies
• between the orbits of Mars
• Jupiter.
• Jupiter is the most massive
• body in our solar system after
• the Sun, and it therefore exerts a substantial
  amount of gravity on the objects around it.
• The competing gravitational influence of Jupiter
  and the Sun did not allow the bits and pieces of
  the asteroid belt to accrete into a larger
  planet.

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What type of planet would the asteroid belt be if
it became a planet?

• Probably a rocky planet similar to Mars, except
  smaller. All the asteroids combined are not as
  much mass as Mars is.

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Earth

• A meteor is a bright streak of light that appears
  briefly in the sky.
• Observers often call meteors shooting stars or
  falling stars because they look like stars
  falling from the sky.
• A meteor appears when a particle or chunk of
  metallic or stony matter called a meteoroid
  enters the earth's atmosphere from outer space.

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Earth

• Why was early Earth hit with so many meteors than
  the current Earth?
• They delivered enough carbon dioxide and water
  vapor to turn the atmosphere of planets into
  warmer and wetter environments that were more
  habitable for life.
• Also, increased
• Earths size and
• caused thermal
• energy.

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Why can Earth support life?

• (1) the Earth has the right conditions (such as
  carbon and a temperature that allows liquid
  water)
• It is at a perfect distance from the Sun not too
  hot, not too cold. A temperate climate.
• Earth is 94 million miles (150 million km) from
  the Sun.
• Ideal gravity which makes moving about easy
  without the difficulty of heavy gravity and low
  gravity. Earth's diameter is 7,926 miles (12,756
  km).

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Life Cycle of Stars
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• Stars are born in
• nebulae. Huge clouds
• of dust and gas
• collapse under
• gravitational forces,
• forming protostars.
• These young stars
• undergo further
• collapse, forming main
• sequence stars.

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• Stars expand as they
• grow old.
• -As the core runs out
• of hydrogen then
• helium, the core
• contacts the outer
• layers expand, cool,
• become less bright.
• This is a red giant
• or a red super giant
• (depending on the initial mass of the star). It
  will eventually collapse and explode.
• - Its fate is determined by the original mass of
  the star it will become either a black dwarf,
  neutron star, or black hole.

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• H-R
• Diagram
• - O and B stars are uncommon but very bright
• - M stars are common but dim..

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• The Hertzsprung -Russell (H-R) Diagram is a graph
  that plots stars color (spectral type or surface
  temperature) vs. its luminosity (intrinsic
  brightness or absolute magnitude). On it,
  astronomers plot stars' color, temperature,
  luminosity, spectral type, and evolutionary
  stage.

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• This diagram shows that there are 3 very
  different types of stars
• Most stars, including the sun, are "main sequence
  stars," fueled by nuclear fusion converting
  hydrogen into helium.
• For these stars, the hotter they are, the
  brighter.

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• As stars begin to die, they become giants and
  supergiants (above the main sequence).
• These stars have depleted their hydrogen supply
  and are very old.
• The core contracts as the outer layers expand.
  These stars will eventually explode (becoming a
  planetary nebula or supernova, depending on their
  mass) and then become
• white dwarfs, neutron stars, or
• black holes (again
• depending on their mass).

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• Smaller stars (like our Sun) eventually become
  faint white dwarfs (hot, white, dim stars) that
  are below the main sequence.
• These hot, shrinking stars have depleted their
  nuclear fuels and will eventually become cold,
  dark, black dwarfs.

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Parallax

• is the apparent change in the position of a star
  that is caused only by the motion of the Earth as
  it orbits the Sun.

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Agriculture Implication

• Earth only planet currently suitable for Ag
• As of the year 2000, about 37 percent of Earth's
  land area was agricultural land.
• Characterizes land's suitability for agriculture
  based on physical parameters like climate, soil,
  and topography.
• Unsuitable land surfaces for growing is subject
  to some soil, terrain, and/or climate
  limitations.

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Agriculture Implication

• How is animal breeding cycles
• impacted by the rotation of Earth?
• Sheep are seasonal breeders, with the majority
  being short-day breeders that cycle in the fall
  and lamb in the spring of the year.
• However, some breeds of sheep will cycle in the
  spring and have lambs in the fall.
• Through the eye of the sheep, its brain perceives
  day length and sends appropriate signals
  (hormones) to the reproductive system to begin
  the breeding season.