Download Vocabulary - Understanding Revolution in our Solar System

Vocabulary - Understanding Revolution in
our Solar System
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Universe
Galaxy
Solar system
Planet
Moon
Comet
Asteroid
Meteor(ite)
Heliocentric
Geocentric
Satellite
Terrestrial planets
Jovian (gas) planets
Gravity
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Revolution
Kepler’s Laws of orbits
Orbit
Ellipse
Eccentricity
Foci (focal points)
Major axis
Apogee
Aphelion
Perigee
Perhelion
Orbital speed
Astronomy
Cosmology
ORBITS work according to very set
mathematical rules.
Kepler figured this all out and gave
us the laws of orbital motion!
Remember, gravity is the force of revolution.
Gravity makes the world go around the sun and keeps
us, the atmosphere, and everything else firmly in place.
 Closer together or bigger mass means
stronger gravity field
 Further apart or smaller mass means
weaker gravity field
 It’s a mass and distance thing!
The elliptical shape of the orbits
and gravity are the key to
understanding a satellite’s speed
in orbit, so let’s first investigate
the orbit shape – an ellipse!
Which of these shapes is
an ellipse?
Draw some ellipses.
Be sure to number
the foci and the
ellipses so you know
how they relate.
What happens to the shape of the ellipse when
the foci are close together or far apart?
Using this simple change from circular
orbits to elliptical orbits, the theory of
revolution was updated to match the
observations of astronomers!
Finally, the math could be done and
Kepler’s Laws of Orbits unified the
heliocentric theory and revolution!
Of course, it took Newton, and eventually
Einstein, to figure out gravity made it
work…but that’s another story!
KEPLER’s LAWS of ORBITS
e = distance between foci
length of major axis
LAW 1 - ORBIT SHAPE: Orbit’s shape is slightly
elliptical and is mathematically described its
eccentricity (e)
KEPLER’s LAWS of ORBITS
LAW 2 - SATELLITE’s SPEED in ORBIT: closer = faster
and further = slower because gravity field is stronger
when a planet is closer to sun
• Fastest at perigee (closest place on orbit path)
• slowest at apogee (farthest away).
KEPLER’s LAWS of ORBITS
LAW 3 - ORBIT SIZE: uses math to say that
further away from sun results in a bigger orbit
and a longer year!
The elliptical shape of the orbits
and gravity are the key to
understanding a satellite’s speed
in orbit, so let’s start with Kepler’s
first law of orbits
Which of these shapes is
an ellipse?
But this is
an ellipse,
too!
WHY?
We usually think of extreme
ELLIPSES like this
CIRCLE with
one center
point and an
EQUAL RADIUS
and DIAMETER
in all directions
REVIEW
Ellipses DO NOT
HAVE one “radius”
CIRCLE with
one center
point and an
EQUAL RADIUS
in all directions
 Ellipses HAVE
UNEVEN
DIAMETERS in
different
directions
Ellipses HAVE TWO
FOCAL POINTS (FOCI)
along their major axis at
their “center”
But ellipses are not circles!
SOME TERMS FOR ELLIPSES
MAJOR AXIS is
the LONGEST
DISTANCE and goes
through the two
focal points (foci)
FOCAL POINTS (FOCI) are
the 2 mathematical
“center” points along the
major axis
Why is the sun in this
picture? It’s one of the
foci in the solar system.
The other focal point is
just math!
Draw some ellipses.
Be sure to number
the foci and the
ellipses so you know
how they relate.
What happens to the shape of the ellipse when
the foci are close together or far apart?
Eccentricity = a measure of how
circular or elliptical an orbit is
Eccentricity (e) = _distance between foci (d)
length of the major axis (L)
MAJOR AXIS is
the LONG DIAMETER
FOCAL POINTS (FOCI)
are the 2 “center”
points.
Now calculate the
eccentricity of two
of the ellipses you
drew…
Mathematically,
what happens to the
shape of the ellipse
when the foci are
close together or far
apart?
When measuring with the ruler,
round to tenths of a centimeter
After calculating, round
eccentricity to thousandths
Let’s make sure we get it!
Lab – Elliptical Path
Note: this concept is 1/3 of your lab test in June!
Eccentricity (e) = _distance between foci (d)
length of the major axis (L)
FOCI CLOSE TOGETHER
 LOOKS MORE CIRCULAR
 Call it SLIGHTLY ELLIPTICAL
 LESS ECCENTRIC
 e closer to 0
FOCI FURTHER APART
 LESS CIRCULAR
Call it MORE ELLIPTICAL
 MORE ECCENTRIC
 e closer to 1
Are the orbits of the
planets around the sun
very elliptical or only
slightly elliptical? Is
there a difference
between terrestrial and
jovian planets?
Are the orbits of the planets very elliptical? Is there a difference in
eccentricity between terrestrial and Jovian planets’ orbits?
1. Get your evidence first!
 Rank the planets’ orbits in order of increasing eccentricity. Do they
group together?
 Calculate the average eccentricity for all the planets in our solar
system, the Jovian planets, and the terrestrial planets.
MAKE A DATA TABLE to summarize your results!
GROUP
ALL PLANETS
TERRESTRIALS
JOVIANS
MOST ECCENTRIC
LEAST ECCENTRIC
AVG ECCENTRICITY
Which planets’ orbits are least
elliptical and most elliptical?
Larger eccentricity values mean
orbit is more elliptical.