Download Distances in Space

Distances in
Space
Interplanetary Distances
• Compared to how far away the stars are,
separation of the planets is a relatively
small distance.
• Examples: Distance from Earth to the
Sun ~150 000 000 km and the distance
between Earth and Mars is 75 000 000
km.
• Units of Distance used to describe the
distance between planets is Kilometers
• Kilometers are of limited use because distances
in space are very large and we usually must
express the number of kilometers in scientific
notation.
e.g. the average distance from Earth to the Sun is
150 000 000km, but we write it 1.5x108km
Bill Nye distances between planets (4:17 min): http://www.youtube.com/watch?v=97Ob0xR0Ut8
Bill Nye distances between planets soccer field (2:07 min): http://www.youtube.com/watch?v=BdAqq-wEQV0&feature=related
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1 astronomical unit = 1 AU
1 AU = average distance between Earth and Sun
Earth is 150 000 000 km, or 1 AU away from the Sun.
Mars is 230 000 000 km, from the sun, or approximately 1.5
a.u. from the Sun. So Mars is 1.5 times as far from the sun as
Earth is from the sun.
Why use the sun as a reference
point?
Interstellar Distances
• Interstellar distances are relatively very,
VERY large distances.
• Examples: Distance between Earth and
Alpha Centauri (the next closest star) is
3.8x1013 km [or 38 000 000 000 000 km]
• Units of Distance used to measure the
distance from Earth to a star or galaxy are
LIGHT YEARS
• 1 light year is the distance that light
can travel in 1 year, at its speed of
300 000 km/s
• 1 light year = 9.5x1012 km
b
• Example: The nearest star (other than
the Sun) to us is Alpha Centauri. Alpha
Centauri is 4.3 light years away or
4.3x9.5x1012 km = 3.8x1013 km away
from earth.
• This means that the light that we see
from Alpha Centauri left that star 4.3
years ago.
Is that like
looking into the
past?
2.2 million light
years
• The Andromeda Galaxy is 2.2 million light years away from
Earth.
• This Means that the light we see from Andromeda Galaxy left
there 2.2 million years ago.
• It is therefore very possible that some of the stars in
Andromeda have exploded as a supernova or gone out long
ago. The message of these star finishing events just has not
gotten to us yet!