Transcript Unit 8: Astronomy

Unit 8: Astronomy
A Trip Through the Solar System
The Universe
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A solar system is a star and all the
celestial objects that orbit that star.
A galaxy is a cluster of billions of stars in a
general location in space.
The Universe is composed mostly of
empty space and hundreds of billions of
galaxies.
The Milky Way Galaxy
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A spiral galaxy.
The Sun is located on
one of the spiral
arms.
It is believed that a
black hole is located
in the center of the
galaxy.
Our Star, the Sun…
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At the center of the solar
system lies the Sun, the
solar system’s most
massive object.
The Sun gets it’s energy
by nuclear fusion.
The Sun fuses Hydrogen
atoms into Helium atoms.
The Sun is one of billions
of stars in The Milky Way
Galaxy.
Mercury
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The closest planet to
the Sun
Has many impact
craters much like the
moon
Almost no
atmosphere to speak
of
No moons
Venus
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Very similar to Earth
in terms of size,
density and mass
Cannot see the
surface of Venus due
to thick cloud cover
Atmosphere made of
96% carbon dioxide
results in very hot
temperatures
Earth
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Atmosphere contains
free oxygen allowing
life to exist
Only place where life
has been found so far
You should know a lot
about this planet by
now!
Mars
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The last of the terrestrial
planets
Very thin atmosphere
made primarily of carbon
dioxide
Very cold compared to
Earth, and about half the
size
Reddish appearance
from oxidation of minerals
such as iron
Mars has 2 moons
Asteroid Belt
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Located between Mars and
Jupiter are the rocky remains
of a Planet that never formed.
An asteroid that escapes the
belt is called a meteor.
A meteor that lands on a
planet is called a meteorite.
Most meteors burn up in the
Earth’s Atmosphere and are
called “shooting stars”.
Jupiter
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The first of the Jovian (Jupiterlike) planets
Largest planet in the solar
system
Jupiter’s atmosphere is made
of mostly hydrogen and helium
(much like a star)
The Great Red Spot on Jupiter
is a hurricane-type feature
about 4 times the diameter of
Earth
Jupiter has 16 moons
Saturn
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Also a gas giant (Jovian)
planet
Has spectacular rings
made of ice, rocks and
dust
Radiates more energy
than it receives from the
Sun due to tremendous
pressure in it’s interior
Saturn has 18 moons
Uranus
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Uranus is the third
Jovian planet
Also has rings, but
not as prominent as
Saturn’s
Axis is tilted by 98°,
so one pole is always
facing the Sun
Uranus has 21 moons
Neptune
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The outermost gas giant
(Jovian planet) in the
Solar system
Atmosphere made mostly
of hydrogen and helium,
but also methane which
gives the planet a blue
color
Strongest winds in the
solar system estimated at
2,500 km/hr
Neptune has 8 moons
Pluto
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Smallest of the planets
with a very eccentric orbit
makes “planet” status
debatable (recently
kicked out).
Smaller than our moon
Sometimes closer to the
Sun than Neptune
Has one moon that is
more than half it’s size –
very unusual
Comets
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Considered part of our
solar system because
they orbit our Sun.
Ice and debris that make
a very eccentric orbit
around the sun.
When a comet is close to
the sun its tail ignites and
becomes visible.
Hailey’s Comet returns
into view every 75 years.
Comet Orbit
Average Densities of the Planets
The graph on the right
shows the average
densities of the
planets (Mercury on
the left and Pluto on
the right).
 Which four planets
are densest?
 Which four are least
dense?
 Which planet could
float in water?
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5
Average
Density
3-D Column
2
3-D Column
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4
3
2
1
0
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