Download A Guide to the Solar System Relative Sizes of the Sun and Planets

A Guide to the Solar System
Solar System
on a shoe string budget
Earth, as viewed by the
Voyager spacecraft
Reading: Chapter 12
Relative Sizes of the Sun and
Planets
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The Sun
•
•
•
•
Radius: 108 x radius of Earth
Mass: 333,000 x mass of Earth
Over 99.9% of solar system’s mass
Surface temperature 5800 K
The Sun
• Composition: 98% hydrogen and helium, 2% other
elements
• In 1 second the Sun produces a million times the total
energy used in the US in 1 year !
2
Mercury
0.4 AU from sun
0.38 x radius of Earth
0.055 x mass of Earth
• Made of metal and rock; large iron core, no atmosphere
• Desolate, cratered
• Very hot and very cold: 425°C (day), –170°C (night)
• Rotates 3 times in every 2 orbits around the Sun
Venus
0.7 AU from sun
0.95 x radius of Earth
0.82 x mass of Earth
• Extreme greenhouse effect: Hotter than Mercury: 470°C,
day and night
• Atmospheric pressure like 1km underwater!
• No oxygen or water
3
Earth
• An oasis of life
• The only surface liquid water in the solar system
• A surprisingly large moon
Mars
1.5 AU from sun
0.53 x radius of Earth
0.11 x mass of Earth
• Looks almost Earth-like, but don’t go without a spacesuit!
• Giant volcanoes, a huge canyon, polar caps, more…
• Water flowed in the distant past; could there have been life?
• Dramatic Mars movies and simulations:
maasdigital.com/gallery.html
esa.int/SPECIALS/Mars_Express/SEMINCO7BTE_0.html
4
Jupiter
5.2 AU from sun
11.2 x radius of Earth
318 x mass of Earth
• Much farther from
Sun than inner
planets
• Mostly H/He; no
solid surface
• 300 times more
massive than
Earth
• Many moons,
rings …
Jupiter
Jupiter’s moons
can be as
interesting as
planets
themselves,
especially
Jupiter’s four
Galilean moons
• Io: Active volcanoes all over
• Europa: Possible subsurface ocean
• Ganymede: Largest moon in solar system
• Callisto: A large, cratered “ice ball”
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Jupiter
Jupiter's Ring System
Jupiter's Ring System
Saturn
9.5 AU from sun
9.4 x radius of Earth
95.2 x mass of Earth
•
•
•
•
Giant and gaseous like Jupiter
Spectacular rings made of ices and rocks
Many moons, including cloudy Titan
Cassini spacecraft currently studying it
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Saturn
Cassini’s view of Saturn with the Sun behind it
Can you spot Earth ?
Saturn
Cassini’s view of Saturn with the Sun behind it
Now can you spot Earth ?
Check out saturn.jpl.nasa.gov/home/index.cfm for more
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Uranus
19.2 AU from sun
4 x radius of Earth
14.5 x mass of Earth
• Smaller than
Jupiter/Saturn;
much larger than
Earth
• Made of H/He gas
& hydrogen
compounds
(H2O, NH3, CH4)
• Extreme axis tilt
• Moons & rings
Neptune
30.1 AU from sun
3.9 x radius of Earth
17.1 x mass of Earth
• Similar to
Uranus (except
for axis tilt)
• Many moons
(including
Triton)
• Has rings
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Pluto: A Dwarf Planet
39.5 AU from sun
0.18 x radius of Earth
0.0022 x mass of Earth
•
•
•
•
•
Much smaller than other planets: Dwarf planet
Icy, comet-like composition
Its moon Charon is similar in size
The plane of its orbit is tilted
Other dwarf planets: Eris, Ceres
9
Motion of Planets
• All planets in
the solar system
orbit in the
same direction
and in nearly
the same plane
• Most also rotate
in that direction
Two Main Planet Types
• Terrestrial planets
are rocky,
relatively small,
and close to the
Sun
• Jovian planets are
gaseous, larger,
have rings and are
farther from Sun
10
Notable Exceptions
• Several
exceptions to
the normal
patterns need to
be explained
Small Bodies in the Solar System
• Small bodies, the leftover “scraps” from the formation of the
Solar System, fall into three distinct groups:
1 asteroids
• rocky or metallic in composition
• most are located between the orbits of Mars and Jupiter
http://www.nasa.gov/mission_pages/WISE/multimedia/pia12469.html
11
Small Bodies in the Solar System
2 Kuiper belt comets
• made mostly of ice
• orbit the Sun beyond
Neptune
• orbit in same
direction and plane as
the planets
3 Oort cloud comets
• made mostly of ice
• orbit at the outer
fringe of the Solar
System
• spherically distributed
about the Sun
Properties of Asteroids
• They are small in size.
• the largest one, Ceres, (now a dwarf planet) is only 1,000 km
across
• They are not spherical in shape.
• shaped more like “potatoes”
• gravity not strong enough to compress rocky material
• odd shapes imply that some are fragments from asteroid
collisions
• Small asteroids are more
common than large asteroids.
• All the asteroids in the solar
system wouldn’t add up to
even a small terrestrial planet.
12
Rocks Falling from the Sky
• meteor – a trail of light caused by a particle which enters
Earth’s atmosphere.
• most of these particles are the size of a pea
• they completely burn up in Earth’s atmosphere
• meteorite – a rock which is large enough to have survived its
fall to Earth
• they caused a brighter meteor…sometimes called a fireball
• How can you tell that you have a meteorite?
– they have a higher metal content than terrestrial rocks
– they contain Iridium and other isotopes not found in
terrestrial rocks
Comets
• Comets are icy
counterparts to asteroids.
• Unlike planets, they are
not confined to the ecliptic
and disappear after several
weeks
• Most comets remain
perpetually frozen in the
outer solar system.
• Only comets that enter the
inner solar system grow
tails.
13
Composition and Structure of Comets
•
Comets are “dirty snowballs”…ice mixed with rock and dust.
• ices are H2O, CO2, CO, NH3 , CH4
•
nucleus
• the “dirty snowball”
• how the comet appears far
from the Sun
•
coma
• surrounds nucleus when near
the Sun
• sublimated gas & dust
•
plasma tail
• ionized gas swept back by
Solar wind
•
dust tail
• dust particles swept back
more slowly by radiation
A Comet’s Journey
14
Meteor Showers
• Earth is impacted by an estimated 25 million small particles
each day which cause meteors.
• When the Earth passes through the trail of a comet, the
number of particles impacting the Earth’s atmosphere
increases. We call this a meteor shower.
Perseid meteor
shower against the
backdrop of an
aurora, (2000).
Meteor Showers
• Showers occur on the same dates each year, corresponding to
when the Earth crosses a given comet’s orbit.
• The meteors appear to emanate from one point in the sky.
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