Download Planets

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The Solar System
The Planets
The word “Planets” comes from the Greek word for
“wandering stars”. The stars are fixed in the sky, holding
their same positions year after year, but the planets move
over days across the background of the starry sky.
The planets known to ancient people were often brighter
than the stars, and were given the names of Gods.
In the summer of 2006, the International Astronomical
Union announced three criteria for an object to be
labeled a “planet”:
1.
2.
3.
It must be massive enough to be spherical
It must orbit the Sun
It must be dominant (massive) enough to have
cleared all other objects out of its orbit
Big objects not meeting these three criteria (like Pluto)
Would be classified as “dwarf planets”
There are five currently named “dwarf planets”:
Ceres is the largest asteroid in the asteroid belt.
Four are called “plutoids” and are beyond Neptune,
Pluto, Haumea (2004), Eris (2005), and Makemake
(2005).
Mercury
1/3rd the size and mass of Earth, about the size
of the Moon
Grey/yellow in color, similar to the moon
No atmosphere
Day temperature: 800° F
Day: 58.6 days
night: -300° F
Year: 88 days
Only visible in the sky for a shortwhile before sunrise
near the Sun or after sunset near the Sun, because
Mercury is so close to the Sun.
Looks like the Moon with lots of craters
No moons or rings
A little less gravity than Earth, a little bit smaller
White in color
Venus has a thick, cloudy atmosphere of carbon
dioxide and sulfuric acid. Surface air pressure is
90 times that of Earth
Surface temperature reaches 900° F
225 day year, 243 day retrograde “day”
Earth’s “sister” planet
The brightest object in the sky, besides
the Sun and Moon. Venus is the
“morning” or “evening” star, being a
very bright, white “star” in the morning
or evening sky.
Venus
Earth
A blue and white planet
Nitrogen / oxygen atmosphere
Average temp.: 59° F
365.26 day “year” , 23.93
hour “day”
One satellite called “the Moon”. The planet is often referred to as the Earth-Moon
System, because the Earth and moon are similar in size and close to each other.
The only planet known by humans to have “life”
A mostly water planet
1/2 the size of Earth, 1/3 the gravity
A red planet, because of a large
amount of iron oxide (rust) in the
soil
Mars
A VERY thin atmosphere, mostly CO2
Day: 24 hrs, 37 min. Year: 687 days
The temperature on Mars ranges
from about 0° to -100° F
Two moons: Phobos and Deimos...
both are very small (less than 30 miles
across) and appear to be irregularly
shaped asteroids captured by the
Martian gravity
Mars has polar ice caps,
volcanoes and seasons
Deimos and Phobos
Taken by the “Spirit” Rover
Asteroids
315x Earth’s gravity, 11x bigger
Jupiter
Gas Giant, atmosphere of mostly
hydrogen and helium with a
liquid metallic core
Temperature in the upper clouds
is -220° F, and increases as you
approach the core to 43,000° F
Year is 11.86 Earth years, day
is 9.92 hours
63 known moons, the inner 4
being as large as Earth’s moon
and visible with Earth telescopes
Thin ring, 10 meters thick
made of rock and dust
Jupiter and Io
Ganymede
Io
Jupiter’s Ring
Tvashtar erupting on Io, 2/28/07 as New Horizons flew by
95x the gravity of Earth, 9x wider
Atmosphere of hydrogen and helium
with a liquid metallic core
Average temperature of -300° F
Year of 29.46 Earth years,
day of 10.66 hours
60 moons, including Titan, a
moon bigger than Mercury
with a Nitrogen atmosphere
and a solid and liquid surface.
Saturn’s density is so low it
would float on water
Saturn
Dione
Rings
Enceladus
Icy H2O on its surface
Lack of craters suggests
it has been resurfaced
Cassini photographed an H2O
geyser
Titan
Methane rain with dry
stream and lake beds where
methane has flowed and
then evaporated
Nitrogen atmosphere
10x thicker than Earth
A possible volcano
Conditions like
ancient Earth
Huygens photographed dry
river channels and
lakebeds, presumably from
raining methane
Titan must have an
internal source of methane,
as UV light from the Sun
turns it into solid organic
material
Huygens observed no
actual liquid and only a few
clouds through the haze
Titan from Huygens 1/05
Cassini discovers Saturn’s 60th moon, July 2007.
It is 1.2 miles across. This was filmed over 6 hours.
Gravity 14.5x greater
than Earth, 4x wider
Methane atmosphere
Surface temperature
of -345° F
Year: 84 Earth years
Day: 17.24 hours
Uranus
Five major moons, at
least 9 more smaller
moons
More on Uranus
Has a ring system
Tilted almost 90
degrees on it’s axis
Each season lasts 21 years. In summer,
the Sun would never set, in winter it
would never rise.
Neptune
17x the Gravity of
earth, 4 x wider
Atmosphere of
methane, hydrogen
and helium
Temperature of -373° f
Year of 165 earth years, day of 16 hours
Neptune has 2 major moons 6 small ones and rings
NeptuNe’s riNgs
Neptune and Triton
Triton
Pluto
Earth has 500x the gravity, and is 5.5x bigger
Very thin atmosphere of methane and nitrogen
Surface temperature of -390° f
248 years to revolve around the Sun,
days to rotate
6.4
Pluto has a highly elliptical orbit orbit
Five moons: Charon (1978), Hydra (2005), Nix (2005),
P4 (2012), P5 (2012)
The Kuiper Belt and Oort Cloud
Comets
Balls of ice and dust on highly
elliptical orbits around the sun
Comet
Tempel 1
Sedna
Sedna is three times farther than Pluto, a giant
iceball on a highly elliptical orbit
Quaoar (2002) is a another Kuiper Belt
object
Varuna is another about the same size
UB313 2003 “Eris”
Identified in the summer of 2005 as a
“planet”
Bigger than Pluto
More than twice as far as Pluto, on
average
The Orbit of Eris
(bigger than Pluto and sometimes closer)