The Solar System
Chapter 19, 20, & 21
Please write down all the underlined
items. Abbreviate to save time.
1
What is Astronomy?
1. Astronomy is the study of the universe.
– This includes planets, stars, galaxies, black
holes, moons, meteors, comets, asteroids and
all of the matter that exists in space.
2. Astronomers are people who observe &
study space.
2
Modern Calendar
1. Our modern calendar is based on the
observations of bodies in our solar system.
2. A year is the time it takes for the Earth to orbit
the sun; year = revolution.
3. A month is the time it takes for the moon to orbit
the Earth.
4. A day is the time it takes for the Earth to rotate
once on its axis; day = rotation.
3
The Size and Scale of our Universe
It is important to consider scale when we
think about the universe.
Stars appear to be very small when viewed
from Earth, but they are actually very
large, some, like our sun, are bigger than
Earth.
4
The Scale of our Solar System
Earth
5
Scale of the Universe
SUN
Mercury
6
Our Galaxy and Scale
• Our Milky Way galaxy is huge.
• Let's now pretend that our galaxy is a kid's
sandbox, and our sun is a grain of sand in a
sandbox.
– The Earth is a dust speck near the grain of sand, too
small to be seen without a microscope.
– If our sun were a grain of sand in this sandbox
representing the Milky Way galaxy, the sandbox
would be somewhat oval and yet flat, and would be
about 20 feet in diameter.
– The sand would be about 12 inches thick in the
center, and thinner towards the edges.
7
THE MILKY WAY GALAXY: our
•Each swirling object
you see is a galaxy in
our universe.
1. We can estimate that
there are about 100
billion stars in our
galaxy.
2. Andromeda is the
nearest major galaxy to
our own Milky Way
Galaxy.
3. Most scientists
believe that Andromeda
is about 2 million light
years away from the
Milky Way.
8
Milky Way Galaxy: home to our solar system
9
Distance in Space
1. Distance in space—mainly distance outside of
our solar system—is measured in light years.
Example: distance to another star; which is a very,
very, large distance
2. A light year is the distance light travels in a
year, 5.88 trillion miles. IT IS NOT TIME!!!
3. Light travels at 186,000 miles/sec or 300,000
km/s.
4. If it takes the light from a star 15 years to reach
you, then how far away is the star?
10
Distance from the Sun to Earth =
An Astronomical Unit
• The distance from the Sun to the Earth is
93 million miles.
– 93 million miles = 1 astronomical unit
– 1 astronomical unit = (150 million kilometers)
• this is the unit of measurement for
distances b/w planets in our solar system
11
Astronomical Unit (AU) for the
planets
Average Distance from the Sun
Planet
(measured in AU)
Mercury
0.39
Venus
0.723
Earth
1.0
Mars
1.524
Jupiter
5.203
Saturn
9.539
Uranus
19.18
Neptune
30.06
12
The Sun: The Center of Our Solar
System
• Wider than 100 Earths
• 10,000 °F on surface & 27,000,000 °F in
its core
• less bright & massive than the very largest
stars
13
Different Views of The
Sun
3-D Image of the sun
Normal Telescopic
Image of the sun
14
UV Image of the sun
Just what is a planet anyway? Well, according to
The International Astronomical Union
The IAU therefore resolves that planets and other bodies in
our Solar System, except satellites be defined into three
distinct categories in the following way:
(1) A "planet“ 1 is a celestial body that (a) is in orbit
around the Sun, (b) has sufficient mass for its selfgravity to overcome rigid body forces so that it
assumes a hydrostatic equilibrium (nearly round)
shape, and (c) has cleared the neighborhood around
its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in
orbit around the Sun, (b) has sufficient mass for its selfgravity to overcome rigid body forces so that it assumes
a hydrostatic equilibrium (nearly round) shape 2, (c) has
not cleared the neighborhood around its orbit, and (d) is
not a satellite.
15
http://www.iau.org/iau0602.423.0.html
Just what is a planet anyway? Well, according to
The International Astronomical Union
(3)
All other objects, except satellites, orbiting the Sun shall
be referred to collectively as "Small Solar System
Bodies".
1. The eight planets are: Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, and Neptune.
2. An IAU process will be established to assign
borderline objects into either dwarf planet and other
categories.
3. These currently include most of the Solar System
asteroids, most Trans-Neptunian Objects (TNOs),
comets, and other small bodies.
16
http://www.iau.org/iau0602.423.0.html
Distances of the Inner Planets from the
Sun in Astronomical Units (150 million km
= 1 AU)
17
The Inner Planets: the terrestrial
planets; all are dense & rocky
•
•
•
•
Mercury
Venus
Earth
Mars
• They are solids & close to the sun because the
materials that make them can be a solid at high
temperatures.
18
The Inner Planets’ Orbits
19
Mercury
• 1/3 wide as Earth
• No moons; resembles our moon because of all of its craters
• Big, grey rock made of iron
• 2nd hottest planet & smallest
• Revolves around the sun in 88 days; Rotates on its axis every 58
days
– 1.5 days on Mercury = 88 days on Earth
• Temperature varies -173°C to 427°C since it lacks a protective
atmosphere.
• Temperature variations on Mercury are the most extreme in the
solar system.
20
Mercury
In Roman mythology Mercury is the god of commerce, travel and thievery,
the Roman counterpart of the Greek god Hermes, the messenger of the
Gods. The planet probably received this name because it moves so quickly
across the sky.
Mercury has been known since at least the time of the Sumerians (3rd
millennium BC). It was given two names by the Greeks: Apollo for its
apparition as a morning star and Hermes as an evening star. Greek
astronomers knew, however, that the two names referred to the same body.
Heraclitus even believed that Mercury and Venus orbit the Sun, not the
Earth.
http://www.nineplanets.org/mercury.html
21
Venus
• Earth’s twin—its size is almost as big as Earth
• No moons; thick yellow clouds of acid
• Dense nickel & iron planet w/a molten core; covered by
many shield volcanoes (largest one is Sif Mons)
• Hottest planet in solar system at 464°C due to its thick
atmosphere—exerts 90% times more pressure than the
Earth’s atmosphere (would be like being 1km deep in the
ocean to stand on Venus)
• Atmosphere made of carbon dioxide (90%) & sulfuric
acid, which creates a monstrous greenhouse effect.
• Had water @ one point but it all boiled away.
22
Venus
Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty.
The planet is so named probably because it is the brightest of the planets known
to the ancients. (With a few exceptions, the surface features on Venus are named
for female figures.)
Venus has been known since prehistoric times. It is the brightest object in the sky
except for the Sun and the Moon. Like Mercury, it was popularly thought to be two
separate bodies: Eosphorus as the morning star and Hesperus as the evening
star, but the Greek astronomers knew better. (Venus's apparition as the morning
star is also sometimes called Lucifer.)
http://www.nineplanets.org/venus.html
23
Earth
• “Third rock from the sun,” made completely of rock; core
made of iron & nickel; has magnetic field lines
• 1 moon—Luna
• Temperatures range from -13°C to 37°C
• Densest planet in our solar system; has water in all 3
states of matter (solid, liquid,& gas)
• 5th largest planet in solar system
24
Earth
Earth is the only planet whose English name does not derive from
Greek/Roman mythology. The name derives from Old English and
Germanic.
In Roman Mythology, the goddess of the Earth was Tellus - the
fertile soil (Greek: Gaia, terra mater - Mother Earth).
It was not until the time of Copernicus (the sixteenth century)
that it was understood that the Earth is just another planet.
http://www.nineplanets.org/earth.html 25
Aurora Borealis: Earth’s atmosphere
interacts with its magnetic field lines
creating a spectacular light show
26
http://earth.jsc.nasa.gov/sseop/efs/query.pl
Earth’s Moon: Luna (384,400 km from Earth)
Called Luna by the Romans, Selene and Artemis by the Greeks, and many other
names in other mythologies.
The Moon, of course, has been known since prehistoric times. It is the second
brightest object in the sky after the Sun. As the Moon orbits around the Earth once
per month, the angle between the Earth, the Moon and the Sun changes; we see
this as the cycle of the Moon's phases. The time between successive new moons
is 29.5 days (709 hours).
27
http://www.nineplanets.org/luna.html
Mars
• The red planet—red from rust, meaning that it had water on it at one
time
• Once had water on it; has polar ice caps that have both frozen water
& carbon dioxide in them
• Many scientists believe that most of Mars’ water lies frozen beneath
Mars’ soil
• Has 2 volcanoes—Tharsis (8,000 km wide) & Olympus Mons—an
extinct shield volcano; it is the largest volcano in the solar system
• Temperature ranges: -123°C to 37°C
• Revolution: 1 yr, 322 days
• 2 moons: Phobos & Deimos (mean fear & panic)
• Spirit & Endeavor
28
Phobos
Phobos ("FOH bus") is the larger and innermost of Mars' two moons. Phobos is
Greek for “fear.”Phobos is closer to its primary than any other moon in the solar
system, less than 6000 km above the surface of Mars. It is also one of the smallest
moons in the solar system.
29
http://www.nineplanets.org/phobos.html
Deimos
Deimos ("DEE mos") is the smaller and outermost of Mars' two
moons. It is one of the smallest known moons in the solar system.
In Greek mythology, Deimos is one of the sons of Ares (Mars) and
Aphrodite (Venus); "deimos" is Greek for "panic".
30
Mars
Mars (Greek: Ares) is the god of War. The planet probably got this name
due to its red color; Mars is sometimes referred to as the Red Planet.
(An interesting side note: the Roman god Mars was a god of agriculture
before becoming associated with the Greek Ares; those in favor of
colonizing and terraforming Mars may prefer this symbolism.) The name
of the month March derives from Mars.
31
http://www.nineplanets.org/mars.html
Mars—Home to the largest volcano in
the solar system
Olympus Mons is the largest volcano
on Mars. This shield volcano, similar
to volcanoes in Hawaii, measures 624
km (374 mi) in diameter by 25 km (16
mi) high. It is 100 times larger than
Mauna Loa on Earth. Located on the
Tharsis Plateau near the equator,
Olympus Mons is bordered by an
escarpment. The caldera in the center
is 80 km (50 mi) wide and contains
multiple circular, overlapping collapse
craters created by different volcanic
events. The radial features on the
slopes of the volcano were formed by
overflowing lava and debris.
32
http://www.nineplanets.org/mars.html
The Asteroid Belt
• Small, rocky bodies that revolve around the sun
– Made of leftovers from the formation of the universe
• Range in size from a few meters to greater than 900 km
in diameter
• Irregular shapes, but larger ones are spherical
• Most orbit the sun in the asteroid belt—a region of space
b/w Mars & Jupiter
• Asteroids vary in color depending on their location in the
asteroid belt
– Outermost region = reddish brown to black (organic composition)
– Innermost region = gray (carbon); light gray = stony/metallic
33
Famous Asteroids
Hektor
Ida and Dactyl
http://neo.jpl.nasa.gov/images/ida.html
34
Ceres: the largest of the asteroids
Observations of 1
Ceres, the largest
known asteroid, have
revealed that the object
may be a "mini planet,"
and may contain large
amounts of pure water
ice beneath its surface.
http://www.spaceflight
now.com/news/n0509/
07ceres/
35
Meteoroids: “cousins” to asteroids;
shooting stars
• Much smaller than asteroids
but very similar
• Meteoroids are small, rocky bodies that
revolve around the sun.
– Once it enters Earth’s atmosphere it becomes
a meteor & stays a meteor if it burns up in the
atmosphere.
– If it strikes the ground it is a meteorite.
36
Meteoroids continued
• 3 types:
– Stony(Rocky)—rocky material
– Metallic—iron & nickel
– Stony-iron—rocky, iron & nickel
37
Stony (Rocky) Meteorites: most
primitive; contain water
38
http://meteorites.asu.edu/images/new-concord-big.jpg
Metallic Meteorites
http://www.astro.virginia.edu/class/oconnell/astr121/im/iron-meteorite.jpg
39
Stony-iron Meteorites
http://www.gpc.edu/~pgore/myphotos/rocks/stonyironmeteor.jpg
40
Meteorite Crater
In Canyon Diablo in Arizona, USA, you can visit the best preserved meteorite crater on
earth. It was formed about 22,000 years ago by the impact of a giant metallic nickel-iron
meteorite, which arrived from space at a speed of about 50,000 kilometers per hour, and
weighed many hundreds of tons. Friction with the atmosphere does not really slow such
a mighty mass, which smashed into the solid earth, punching away 300 million tons of
rock in a mighty blast which left a crater which even today is still 1.5 kilometers in
41
diameter and 170 meters deep.
(http://www.rocksonfire.com/About-Meteorites.htm)
Stars Fell On Alabama,
November 12, 1833, Leonid Meteor Shower
•
•
•
New car license plate introduced in January, 2002, commemorating this.
The new slogan on these plates is "Stars Fell on Alabama," in reference to
the 1934 song written by Mitchell Parish and Frank Perkins and made
famous by Ella Fitzgerald and Louis Armstrong, Frank Sinatra, and other
artists over the years.
The top of the plate contains a field of stars and musical notes around the
slogan.
42
http://www.15q.net/al.html
The Outer Planets: The Gas Giants
or Jovian Planets
• Jupiter, Saturn, Uranus, & Neptune
• All are made of gas. They are not solids like the inner
planets.
– They get denser with increasing depth.
• All have rings. Some are barely visible unlike Saturn’s
rings.
• Since their masses are so much larger, they have
more moons than the inner planets.
– Which planet should have the largest number of moons?
43
Distances of the Outer Planets from the
Sun in Astronomical Units
(150 million km = 1 AU)
Jupiter
5.203 AU
Saturn
9.539 AU
Uranus
19.18 AU
Neptune
30.06 AU
Pluto
39 AU
44
Jupiter
• The largest planet in our solar system (318 times as large as Earth)
– Its mass holds the asteroid belt in place & protects Earth from
asteroid assault.
• Made mainly of hydrogen & helium
– Outer part is made of layered clouds of water, methane, &
ammonia
• Radiates more energy into space than it receives from the sun
• Cold planet; average temperature = -110°C
• Great Red Spot (1.5X the size of the Earth) is a storm system similar
to a hurricane that is > 400 yrs old.
• Rotation = 9 hrs, 54 min; Revolution = 11 yrs, 313 days
45
Jupiter continued
• Has 63 moons as of Feb. 2004
• Jupiter probably has a core of rocky material amounting to
something like 10 to 15 Earth-masses.
• Above the core lies the main bulk of the planet in the form of liquid
metallic hydrogen.
• The environment near Jupiter contains high levels of energetic
particles trapped by Jupiter's magnetic field.
– This "radiation" is similar to, but much more intense than, that
found within Earth's Van Allen belts. It would be immediately
fatal to an unprotected human being.
• Has rings like Saturn, but much fainter & smaller
46
Jupiter:
http://www.nineplanets.org/jupiter.html
Jupiter (a.k.a. Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus
and the patron of the Roman state. Zeus was the son of Cronus (Saturn).
Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and
Venus). It has been known since prehistoric times as a bright "wandering star".
But in 1610 when Galileo first pointed a telescope at the sky he discovered
Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as
47
the Galilean moons) and recorded their motions back and forth around Jupiter.
Jupiter’s Rings
http://www2.jpl.nasa.gov/galileo/callisto/p48188.html
Unlike Saturn's, Jupiter's rings are dark. They're probably composed of very small
grains of rocky material. Unlike Saturn's rings, they seem to contain no ice.
48
http://www.nineplanets.org/jupiter.html
Saturn
• 2nd largest planet in the solar system (95 X larger
than Earth)
• Composed mainly of hydrogen & helium w/a small
rocky core
– Methane, ammonia, & ethane are in upper
atmosphere
• Gives off more heat than it gets from the sun
because of the helium falling from its atmosphere—
Saturn seems to still be forming
• Average temperature = -140°C
49
Saturn
• Saturn’s rings are the largest of the gas giants.
– Made of icy particles that range from a few cm
to a few m wide
• Gold, brown,& white; rings gold, brown, white,
red, yellow, & green
• Revolution: 29 years, 155 days
• Rotation: 10 hrs, 42 min
• 31 moons
50
Saturn
In Roman mythology, Saturn is the god of agriculture. The associated Greek
god, Cronus, was the son of Uranus and Gaia and the father of Zeus (Jupiter).
Saturn is the root of the English word "Saturday“.
http://www.nineplanets.org/saturn.html
51
Saturn’s Rings
Saturn’s rings are 250,000 km or
more in diameter & they're less
than one kilometer thick .
http://www.nineplanets.org/saturn.htm
l
52
Uranus
• Super cold -195°C
• 21 moons; 11 rings
• Revolution: 83 yrs, 273 days; Rotation: 17 hrs, 12 min
• 3rd largest planet
• Rotates on its side---planet was probably knocked on
its side after a collision w/an asteroid
– One side points toward the sun & the other in complete
darkness for part of the year
• Made of hydrogen & methane—2 gases that absorb red
light, giving Uranus its distinct blue/green color
53
Uranus
Uranus is the ancient Greek deity of the Heavens, the earliest supreme
god. Uranus was the son and mate of Gaia the father of Cronus
(Saturn) and of the Cyclopes and Titans (predecessors of the Olympian
gods).
Uranus, the first planet discovered in modern times, was discovered by
William Herschel while systematically searching the sky with his
telescope on March 13, 1781.
54
http://www.nineplanets.org/uranus.html
Uranus’ rings
http://hubblesite.org/newscenter/archive/releases/1996/15/image/a/format/web/ 55
Neptune: Big Blue World
• 11 moons
• Rotation: 16 hrs, 6 min.
• Revolution: 163 yrs, 263 days
• Temperature: -200 °C
• Has dark rings
• Neptune & Pluto’s orbits overlap causing
Neptune to sometimes orbit beyond Pluto
56
Neptune: Big Blue World
• Gets its blue color from being made of
methane gas that absorbs red light,
making Neptune appear blue
• Has belts of clouds & a great Dark Spot
similar to Jupiter’s great Red Spot
• Tilted at a 30° angle so its poles are in
light or dark for 40 yrs @ a time
57
Neptune
The Great Dark Spot
In Roman mythology Neptune (Greek: Poseidon) was the god of the Sea.
58
http://www.nineplanets.org/neptune.html
Neptune’s Dark Rings
59
In Roman mythology, Pluto (Greek: Hades) is the god of the underworld.
Pluto was discovered in 1930 by a fortunate accident. Calculations which later turned out to be
in error had predicted a planet beyond Neptune, based on the motions of Uranus and Neptune.
Not knowing of the error, Clyde W. Tombaugh at Lowell Observatory in Arizona did a very
careful sky survey which turned up Pluto anyway.
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/pluto_image.html
60
Kupier Belt (pronounced kew p a)
• A region in space beyond Neptune where @ least 70,000 small, icy,
slow-moving objects orbit the sun
• A region where the planet-building process stopped before any large
objects where formed
• Pluto & is moon Charon (pronounced Sharon) are thought to be
large members of it
• Short-lived comets like Haley’s comet are also thought to come from
the Kupier Belt
• Discovered in 1992 by Dutch-American astronomer Gerard P.
Kupier
61
62
Pluto: the dwarf planet that rotates on its side
• No longer a planet
– Now called a “dwarf planet”—reclassified in 8/2006
• Has 3 moons—Charon, Nix, & Hydra
• Rotation: 6 days, 10 hrs
http://www.nineplanets.org/pluto.html
• Revolution: 248 yrs, 4 days
• Temperature: -225°C
• Covered by frozen nitrogen
• Made of rock & ice
• Less than ½ the size of
Mercury
• Will be visited in 2015
63
Pluto’s largest moon Charon (which is
more than ½ the size of Pluto)
http://pluto.jhuapl.edu/science/ever
ything_pluto/5_looks.php?selectedI
mage=image07.php
Charon is named for the mythological figure who ferried the dead across the
River Acheron into Hades (the underworld).
(Though officially named for the mythological figure, Charon's
discoverer was also naming it in honor of his wife, Charlene.
Thus, those in the know pronounce it with the first syllable
64
http://www.nineplanets.org/pluto.html
sounding like 'shard' ("SHAHR en").
Oort Cloud
• A large sphere that surrounds the solar system
• Where the bulk of comets originate
• Suggested by astronomer Jan Oort in 1950
• Both the Kupier Belt & the Oort Cloud are relatively
pristine remnants of the nebula from which the entire
solar system was formed.
• Could contain as many as a trillion comets
65
http://www.nineplanets.org/kboc.html
66
http://www.astro.rug.nl/~onderwys/ACTUEELONDERZOEK/JAAR2000/oort/oort_cloud.gif
67
http://www.fas.org/irp/imint/docs/rst/Sect19/H_oort-cloud_02,0.jpg
Comets
68
http://www.nineplanets.org/comets.html
Comets
• Comets are sometimes called dirty
snowballs or "icy mud balls". They are
a mixture of ices (both water and frozen
gases) and dust that for some reason
didn't get incorporated into planets when
the solar system was formed. This makes
them very interesting as samples of the
early history of the solar system.
http://www.nineplanets.org/comets.html
69
Comets: When they are near the Sun & active, comets have
several distinct parts:
nucleus: relatively solid & stable, mostly ice & gas with a small
amount of dust & other solids—the icy dirt core
coma: dense cloud of water & gases from the nucleus
hydrogen cloud: huge (millions of km in diameter) but very sparse
envelope of hydrogen
dust tail: up to 10 million km long composed of smoke-sized dust
particles driven off the nucleus by escaping gases; this is the most
commonly seen part of the comet
ion tail: as much as several hundred million km long; composed of
plasma & laced with rays and streamers caused by interactions with
the solar wind
70
Dust
71
Label the parts of a comet: hydrogen
envelope, ion tail, coma, nucleus, & dust tail
72
73
Sedna
• Large planetoid or asteroid
• More than 2X as far from the sun as Pluto
• Huge ball of ice, w/reddish color
• Revolves around the sun once every 10,500
yrs
74
Sedna—what we think it looks like
Sedna's physical composition is a bit of a mystery. You would expect it to be
mostly ices but apparently that's not the case. About all that's known at this
time is that it is very red and that water and methane ices seem to be absent
on the surface.
Sedna is definitely not the "Planet X" that many astronomers anticipated
before the discovery of Pluto. Planet X was supposed to be a much larger 75
object.
http://www.nineplanets.org/sedna.html
Eris—the next “dwarf planet”
• Officially named in 9/2006
• Named for the goddess of chaos &
strife
• 1 moon = Dysomia
• Spirit of lawlessness
76
Xena
• Another planetoid that will probably
become another “dwarf planet” in the
coming months
77