1. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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Name: ___________________________ Period: _____ Date:__________________
Mythology The Sun God. Greeks Called it Hellos
Mass 333 400 times the mass of the Earth
Diameter 1 392 000 km (109 x Earth’s diameter)
Gravity 28 times that on Earth
Surface Temperature
6000°C (average). From 4500 to 2000000°C
up to 15000000°C in the core.
Period of rotation (day) Equator 26 Earth days, poles 37 Earth days
Tilt of axis 122°
A. Which is bigger: Our Solar System or Our Sun?
Naturally our ____________________ is bigger since the sun is apart of it. An
object must always be bigger than something it includes. For example, a shoebox must
always be bigger than the shoes. And your shoe must be big enough to fit your foot.
B. Our Sun:
-The sun is a star.
-A ball of hot glowing gases.
-It gets hotter as you go deeper.
-Central force that has a high
influence on planets orbits.
-Without the sun’s energy and heat
there would be no life on Earth
-It holds everything in place by its
gravity.
-It contains about 99% of the mass of
the solar system.

2. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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C. Our Solar System:
The Solar System includes:
• The Sun, a ______________size, middle-aged star
• The eight planets and associated moons
• ________________chunks of rock found mostly in a belt between Mars and Jupiter
• __________________– mass of frozen gas and rock
• These are considered __________________ which appear in the sky during day and
night.
D. The Formation of Our Solar System:
• ______________________ large cloud of
gas, ice & dust existed
• It began to contract & slowly rotate
• Contraction increased density & rotation
• Gravity began to pull material toward the
center
• Density increases = increased rotation & gravity
• Begins to form disk with large center
• Central mass begins to heat up due to
contraction
• Temperatures reach 10 million °Kelvin
• Hydrogen atoms begin to fuse together forming
Helium
• Fusion occurs, driving the formation of our Sun
• The material outside the central mass forms
planets

3. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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E. The Parts of Our Solar System:
• The ______ is the center of the
Solar System
• _______________, also called
___________: (meaning earth-like)
the first four planets
• __________________: band of
rocks orbiting the sun
• ________________, also called
___________: the four planets
farthest from the sun.
Size Comparison Jovian vs. Terrestrial
Terrestrial Planets:
• Four ___________ planets of the
solar system
• Relatively __________ in size and
mass (Earth is the largest and most
massive)
• __________ surface
• Surface of Venus cannot be seen
directly from Earth because of it’s
_______________________.
Jovian Planets:
• Much _____________ in mass and
size than terrestrial planets
• Much lower average
___________________
• All have rings (not only Saturn!)
• Mostly _________; no solid surface
• Also known as Gas Giants because
they are made of mostly hydrogen
and helium

4. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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Asteroids
• Rocky objects with ____________ or _____________ shapes
• Most orbit in a wide belt between _________ and ____________
• The total mass of all the asteroids is less than that of the Moon
• Believed to be a planet that never formed
• Range in size from dust to almost Moon size
• Photographed by Galileo probe
• Some Named Asteroids:
 Ceres: 940 km (Largest known)
 Pallas: 523 km
 Vesta: 501 km
 Juno: 244 km
 Gaspra & Ida:
Comets:
• Only visible when they are close to the ________
• Icy nucleus, which evaporates and gets blown into space
by solar wind pressure.
• Mostly objects in highly _____________ orbits,
occasionally coming close to the sun
• Comet Composition: Dust, rock, frozen methane, ammonia,
and water
• Comets normally look like dirty ________________
• When they get close to stars, they begin to vaporize &
_______________.
• Forms a coma (tail) from the nucleus (head)
• ___________: glowing trail of particles which always
points away from the star
• Comets eventually break up into space debris
• Oort Cloud: large collection of comets beyond ________
Meteoroids, Meteors & Meteorites:
Meteoroids: chunks of randomly moving through space. Usually leftover comet or
asteroid debris
Meteor: Meteoroid that collides with Earth, evaporates in the atmosphere producing
streaks of visible light (“shooting stars”) Most burn up before reaching
the surface
Meteor Shower: Many meteors at one time
Meteorite: Meteor that does not totally burn up, & strikes the Earth’s surface.
The impact creates a crater

5. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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Planets:
A planet is a body that is in orbit around the Sun, has enough mass for its self-gravity
to overcome forces (nearly round) shape, and clears the neighborhood around its orbit.
Planet order (closest to the sun to furthest): Write one interesting fact about each:
MERCURY: ________________________________________________________
VENUS: __________________________________________________________
EARTH: __________________________________________________________
MARS: ___________________________________________________________
JUPITOR: ________________________________________________________
SATURN: _________________________________________________________
URANUS: _________________________________________________________
NEPTUNE: ________________________________________________________
How do the Planets move around the Sun?
• All planets move in the same plane (a large imaginary flat surface)
• Orbits generally inclined by no more than 3.4o
except for Mercury at 7°
• All planets in almost circular (elliptical) orbits around the sun
• Sense of revolution: counter-clockwise
• Kepler’s Laws govern the planets’ orbits
Orbits
• ____________ – the movement of an object around another object
• __________ – the path taken by a revolving object
• Celestial objects have _______________ orbits
• Velocity changes during revolution; planets further from Sun revolve slower
Elliptical Orbit
• A circle has one central point, called a __________.
• Ellipses have two points, called __________.
• Therefore an ellipse is not a perfect circle.
• Eccentricity is a measure of how off the ellipse is
from being a perfect circle.

6. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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Eccentricity
The _________ of an ellipse is how much it varies from a true circle. The __________
the number, the closer the orbit is to a perfect circle.
Formula for eccentricity:
Eccentricity=
Know when to use your ESRT!
Calculate the eccentricity of the ellipse below:
foci
foci
Regents Question: Which object is located at one foci of the elliptical orbit of Mars?
(1)the Sun (3)Earth
(2)Betelgeuse (4)Jupiter

7. Unit 2: Astronomy Earth Science- Ms. Gill Note Packet #3B
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The Three Kepler’s Laws:
1. Planets move around sun in elliptical orbits. Sun is at one focus point.
2. Planet moves faster when closer to the Sun due to gravitational pull of the Sun.
3.The greater the distance from the sun, the longer the period of revolution because
Longer orbits and Slower orbital velocities.
Orbital Energy
• ______________ – the force of attraction between 2 objects
• ______________ – the tendency of an object in motion to continue in motion
along a straight path
• The interaction of gravity and inertia keep planets in __________
Energy Transfer
• Energy is transferred between ___________ and ______________ as a planet
orbits the Sun.
Orbital Velocity
• The Earth’s orbital velocity is _____________ when kinetic energy is the
highest.
• This occurs when the Earth is ___________ to the Sun in its orbit.
Laws of Planetary Motion
• Devised by German astronomer Johannes Kepler
• He discovered the line joining the Sun and a planet sweeps equal areas in equal
intervals of time