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Ms. Susinno’s Earth Science Class
The scandalous life of Tycho Brahe
https://youtu.be/7QDvKzY4aqA
The planets travel in elliptical orbits around the sun and the sun is
at one focus.
Earth is at
aphelion
around
July 3
Earth is at
perihelion
around
January 3
Hmmm... But why is it warmer when we’re further from the sun?
Apparent
diameter is
larger
Apparent
diameter is
smaller
Not to scale 
The radius between a satellite (the body doing the orbiting) and its primary (the
body it orbits) sweeps out equal areas in equal times.
The Law of Periods: The square of the period of any planet is proportional to the
cube of the semimajor axis of its orbit.
So...
If
This is where
the planet
travels the
fastest
Then
http://astro.unl.edu/classaction/animations/renaissance/kepler.html
Click here
for a
simulation of
all 3 laws!
So...
If the mass of this guy is
doubled....
what will happen to
the gravitational
force between
them?
LABORATORY
SKILL
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BY Alec Marshak & Kyle Harding
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Ellipse- the actual SHAPE that the planet’s orbital path
follows.
a closed loop around two central foci
(one focus, two foci).
Distance between
foci
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major axis
Eccentricity- the NUMBER describing the shape
o e= distance between foci
length of the major axis
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Two pushpins
A piece of computer
paper
A big piece of
cardboard
A 20cm long piece of
string that is tied
together to form a loop
Lastly you need a
pencil
1.
2.
3.
First fold the paper in half like a hot dog then open it and
place it on the cardboard
Now draw two dots that are____centimeters apart in the
middle of the paper (d will be given to you)
Now, follow the directions to mark one focus as the sun.
The lab test is
90% following
directions!
4.
5.
6.
Place the pushpins into the two dots. Make sure to have
pushed the pushpins all the way into the cardboard
Now you will put the string around the pushpins and insert
your pencil inside the string loop
Use it by drawing an elliptical shape while pulling outward
on the string with your pencil (make sure the string stays
on the pins)
Take out the pushpins
8. Now draw a straight line through the middle of the ellipse
connecting the foci to the outside of the ellipse and label it
the major axis
9.Read directions and mark the point on the ellipse where
your planet would travel the fastest
10. Read your directions and compare
Your ellipse to a planet’s ellipse.
7.
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1.
2.
3.
When finding the eccentricity of an ellipse, you use the
equation e=d/l . e=eccentricity, d=distance between foci,
and l=length of major axis. So the steps are…
Measure the distance between the foci.(cm)
Measure the length of the major axis.(cm)
Divide the distance between the foci by the length of the
major axis and the answer is the eccentricity.(cm to the
nearest thousandth)
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So using the steps from the last slide, we will figure out our
ellipse’s eccentricity. The d=2.0 cm and the l= 10.8 cm.Next
we divide 2cm by 10.8cm which equals .185.So our ellipse
has an eccentricity of .185 (rounded to the nearest
thousandths place FOLLOW DIRECTIONS)
Now that we know our ellipse’s eccentricity we can compare
it to another planet’s eccentricity (planet will be given)
Our planet has a less elliptical (more
circular) orbit because the eccentricity of its
orbit is less than the eccentricity of
Mercury’s orbit!
Thank you Alec and Kyle
Be sure to discuss the SHAPE (more or less elliptical)
And the NUMBER (eccentricity is lower or higher)
Example:
More
or less
My planet’s orbit is ________________elliptical
because the orbit’s
Closer to 1 (higher) OR closer to 0 (lower)
eccentricity is _______________.
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Eccentricity is always a decimal.
*if you get a number larger than 1, it is wrong!
(you probably reversed the formula)
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Follow rounding directions!
e has no unit!
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a larger decimal means the orbit’s path is more elliptical
A lower decimal means that the orbit’s path is less elliptical
All of the planets have
slightly elliptical orbits
with the sun at one
focus.
Use your ESRT and
evidence from it to
see which has the
most elliptical orbit!
Pluto (the dwarf
planet) has an orbit
that is much more
elliptical.
Halley’s Comet
Predicted next perihelion:
July 28, 2061
A comet is an icy small Solar System
body that, when passing close to the Sun,
heats up and begins to outgas, displaying
a visible atmosphere or coma, and
sometimes also a tail. These phenomena
are due to the effects of solar
radiation and the solar wind upon the
nucleus of the comet.