Transcript Science 9: Unit E: Space Exploration

Science 9: Unit E:
Space Exploration
Topic 4: Bigger and
Smarter Telescopes
Bigger Telescopes
mitation of early telescopes was that they were
small to see that far into space.
ginning in the 1700s bigger and bigger telescopes
re built to see more detail in the universe.
Herschel Walker used a huge telescope and used
o discover Uranus, the first planet discovered
ce the time of the ancient Greeks.
dern telescopes are often two or more telescopes
mbined together. The images from the different
escopes are combined into a single image by a
per computer.
Adaptive Optics
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A problem with telescopes on Earth is that the moving
atmosphere distorts the image of the stars and
planets; that’s why stars twinkle in the sky.
A way around this problem is to build telescopes where
the atmosphere is thinner like on mountain tops.
Another method is to have a computer measure the
amount of distortion from the atmosphere and change
the shape of the mirror or lens to compensate for the
effect of the moving atmosphere. This is called
adaptive optics and an example of A.O. is the New
Technology Telescope (NTT) in Chile.
To avoid the problem of the atmosphere completely is
to have a telescope out of the atmosphere completely.
This was the reason the Hubble Space Telescope was
built. Having no atmosphere has led to much more
detailed images.
Triangulation
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Triangulation is the method of using
a triangle’s geometry to calculate the
distance to an object you can’t
reach, such as a star.
Triangulation
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Step 1: Create a baseline. Create
two points as far away from each
other as possible where you can still
see the distant object. The longer
the distance between the two points,
the more accurate the measurement.
Triangulation Cont’d
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Step 2: Measure the angles from the
end of the baseline. Use a protractor
to calculate the angle to the distant
object. With stars you need an
astrolabe and compass to calculate
the azimuth-altitude coordinates of
the star.
Triangulation Cont’d
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Step 3: Make a scale drawing of the
triangle you made. Use a protractor
to draw in the correct angles and a
ruler to accurately draw out the scale
model baseline. Make sure you
choose a suitable scale factor. The
altitude of the triangle is the nearest
distance to the distant object.
Triangulation Cont’d
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When triangulating the
distance to stars, the
largest baseline we can
use is the orbit of the
Earth. Therefore the two
angle measurements must
be made six months apart.
Parallax is the apparent
change in position of the
stars as the Earth moves
along in its orbit.
A limitation of triangulating
is that it can only be used
on nearby stars.
Big Distances
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An astronomical unit (AU) is a unit of
distance. It represents the distance from
the sun to the Earth (150 million km).
1 AU = 150 million km.
For example the distance of Pluto to the
sun is 40 AU. The distance of the nearest
star to the sun is about 271000 AU.
An even bigger unit of distance is the light
year. It represents the distance that light
covers in one year. Since light travels at
300’000 km/s this is a very large distance,
about 63’000 AU or 9.5 trillion km. The
North Star is 431 ly away from us.