Distances in Space

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DISTANCES IN SPACE
or Are we there yet?
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Diameter of Earth using common units of length
7,926
12,756
Miles Feet Inches
Kilometers Meters Centimeters
41,849,280
12,756,000
502,191,360 1,275,600,000
Its important to use the correct scale for the
distance you are measuring
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These scales can still be used for relatively
close objects, like the moon, but at 240,000
miles (384,000 kilometers) you can see how large
the numbers are already getting.
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Its very hard for us to understand just how
large the Universe is. Scientists tell us that
the largest number our minds can really
comprehend, or grasp, is about a hundred thousand
(100,000). Because astronomers study objects
over such extremely large distances, they
commonly use units of length that are much bigger
than the ones we usually use. Two common units
of distance used in astronomy are the
astronomical unit (AU) and the light-year.
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Astronomical Unit
The astronomical unit (AU) is the average
distance from the Earth to the Sun, measured to
be about 1.5 x 108 km (150,000,000 km) or
93,000,000 miles. It is a convenient unit to use
when discussing distances within our solar system.
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Saturn has an average distance of 9.5 AU from the
sun. How many kilometers is this? How many
meters?
150,000,000 km X 9.5
1,425,000,000 km
X 1,000
1,425,000,000,000 m
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Pluto is about 6x109 km from the sun. How many
astronomical units (AU) is this?
1 AU______ 150,000,000 km
? AU______ 6,000,000,000 km
40 AU


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Light-year
The light-year is defined as the distance that
light travels in a year. It is equal to a
distance of approximately 9,500,000,000,000 km.
(The speed of light is 300,000 km/sec) For
instance, Alpha Centauri, the closest star to the
Earth after the sun, is 4.3 light-years from us.
How long does it take light from this star to
reach us?
4.3 years
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The star Betelgeuse,
meaning armpit of the giant, is 310
light-years from Earth. How many hours does
light from this star take to reach Earth?
310 yr. X
365 day X year
24 hr. day
not Beetlejuice,
2,715,600 hours
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How many AUs are in a light-year?
9,500,000,000,000 km/light year
150,000,000 km/AU
63,333.33 AU/Light Year
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Parsec
A parsec is an abbreviation for parallax second.
(We will study parallax later) Scientists use
parsecs when even light years are too small to
conveniently express distances. A parsec is 3.26
light-years, or well over nineteen trillion miles
(19,000,000,000,000).
How many AUs are in a parsec?
19,000,000,000,000 miles/Parsec
93,000,000 miles/AU
204,301 AU/Parsec
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http//micro.magnet.fsu.edu/primer/java/scienceopt
icsu/powersof10/index.html