1. Our Place in the Universe

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General Geosciences and Astrophysics
I -Astrophysics-
Marcus Brüggen
1. Our Place in the Universe
TEXTBOOK The Universe, Freedman Kaufmann
Freeman Co.
ISBN 0-7167-9884-0
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Lecture 1 Contents and Scales of the Universe
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1. Our Place in the Universe
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Asteroid

• A relatively small and rocky object which
  orbits a star.

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Comet

• A relatively small and icy object which orbits
  a star.

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Moon

• An object which orbits a planet.

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Planet
A moderately large object which orbits a star it
shines by reflected light. Planets may be rocky,
icy, or gaseous in composition.
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Star

• A large, glowing ball of gas that generates heat
  and light through nuclear fusion

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Solar (Star) System

• A star and all the material which orbits it,
  including its planets and moons

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Nebula
An interstellar cloud of gas and/or dust
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Galaxy

• A great island of stars in space, all held
  together by gravity and orbiting a common center

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Universe

• The total sum of all matter and energy that is,
  everything within and between all galaxies

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Galaxy Cluster
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What does this mean?
1500 light years away!
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Looking back in time

• Light, although fast, travels at a finite speed.
• It takes
• 8 minutes to reach us from the Sun
• 8 years to reach us from Sirius (8 light-years
  away)
• 1,500 years to reach us from the Orion Nebula
• The farther out we look into the Universe, the
  farther back in time we see!

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How large is the Cosmos?

• Lets view it to scale
• say the Sun is the size of a large grapefruit
  (13.9 cm)

Where is the nearest star?
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THE COSMIC CALENDAR
(1 mo 1.17 billion yrs)
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A Universe in motion

• Contrary to our perception, we are not sitting
  still.
• We are moving with the Earth.
• and not just in one direction

The Earth rotates around its axis once every
day!
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The Earth orbits the Sun once every year.
The Earths axis is tilted by 23.5º!
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Our Sun moves relative to the other stars in the
local Solar neighborhood!
Our Sun and the stars of the local Solar
neighborhood orbit around the center of the
Milky Way Galaxy every 230 million years!
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The Milky Way moves with the expansion of the
Universe!

• Mostly all galaxies appear to be moving away from
  us.
• The farther away they are, the faster they are
  moving.
• Just like raisins in a raisin cake they all move
  apart from each other as the dough (space itself)
  expands.

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How have astronomical objects and events
affected life on Earth?
Heres some ideas
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Homework Read page 1-17 in Universe