Transcript astronomy notes

Astronomy and
Cosmology
Where does the Earth fit in?
Formation of the Earth
Formation of the Earth
 Big Bang
Galaxies
Solar Nebulas
Star Formation
Planets
Beginning of Life
Big Bang
 The theory that states the universe
began with a tremendous explosion
 12 bya to 15 bya (billion years ago)
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What is a theory?
 A theory is well-tested and supported
by evidence
 A theory is widely accepted by
scientists
 A theory can be disproved
Galaxies
 Large grouping of stars in space,
formed when chemical clouds gathered
after the Big Bang
 Large galaxies contain more than a
trillion (1,000,000,000,000) stars
Galaxies
 Contain gas clouds, open clusters, and
globular clusters
 Gas clouds are also known as nebulas and
are generally found in spiral galaxies
 Open clusters are groups of newly formed
stars
 Globular clusters are groups of older
stars
Galaxies
 Types
 Spiral
 Elliptical
 Irregular
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 We live in the Milky Way Galaxy
 The Milky Way is a spiral galaxy
 Our sun is about two-thirds of the way
from the center of the Milky Way
Star Formation
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 Gravity collects
hydrogen and
helium to form a
star
 Our sun is an
average sized star
Planetary Formation
 Dust gathers to form planetesimals
 Biggest planetesimal in each orbit
swept up all the dust in that path
 Gas giants collected lots of gases
because of large gravitational pull
 Gases evaporated from inner planets to
leave rocky planet
Planets
 Planets rotate on its axis. One rotation
is one day.
 Planets also revolve around the sun. One
revolution is one year.
 Big enough for its gravity to make it a
ball
 Clear the neighborhood around its orbit
Revolution vs. Rotation
Inner Planets
 Solid planets
 Warmer than outer
planets
 Close together
 Short revolution
 Mercury, Venus,
Earth, Mars
Outer Planets
 Gas Giants
(gaseous)
 Cold
 Far apart
 Long revolution
 Jupiter, Saturn,
Uranus, Neptune
Dwarf Planets
 Past outer planets
 Pluto- formerly a planet
 Ceres-formerly an
asteroid
 UB313 or Xenadiscovered in 2003
The Moon
 The moon does not produce its own
light
 It reflects light from the sun
 Half the moon is always lit, even
though we don’t always see the same
thing in the sky
Phases of the Moon
Lunar Eclipse
 The earth casts a
shadow on the moon
 The moon is in the
full moon position
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Solar Eclipse
 The moon casts a
shadow on the earth
 The moon is in the
new moon position
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Comets
 Small body of ice, rock, and dust
loosely packed together
 Also known as “dirty snowballs”
 Tail forms when comet gets too close
to the sun
 Elliptical orbit
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Asteroids
 Small, rocky bodies that orbit the sun
 Irregular shapes
 Different compositions based on where
asteroid is found in the asteroid belt
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Meteoroid
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 Small, rocky bodies orbiting the sun
 Smaller than asteroids
 A meteoroid is called a meteorite when
it comes into the earth’s atmosphere
and hits the ground
 The streak of light that you see when a
meteoroid enters the earth’s
atmosphere is called a meteor
Distances
 Distances are so far apart in
astronomy, so we use
 Astronomical Units (AU)- average distance
between the earth and the sun or about
150,000,000 km (93,000,000 miles)
 Light Years- distance light travels in one
earth year or 9.5 trillion km
(9,500,000,000,000)
Other Stars…?
 Our nearest star is Alpha Centauri
 It is 4.27 light years away or
40,565,000,000,000 km
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