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Our Solar System I
Origins of the Solar System
Astronomy 12
Learning Outcomes (Students will…)
-Explain the theories for the origin of the solar system
-Distinguish between questions that can be answered by science and those
that cannot, and between problems that can be solved by technology and
those that cannot with regards to solar system formation.
-Estimate quantities of distances in parsec. Estimate the age of the solar
system.
-Describe and apply classification systems and nomenclature used in the
sciences. Classify planets as terrestrial vs. Jovian, inner vs. outer, etc.
Classify satellites. Classify meteoroid, asteroid, dwarf planet, planet.
Classify comets as long period vs. short period. etc
-Formulate operational definitions of major variables. Given data such as
diameter and density describe the properties that divide the planets and
moons into groups.
-Tools and methods used to observe and measure the inner and the outer
planets and the minor members of the solar system
Our Solar System
Our solar system is made
up of:
Sun
Eight planets
Their moons
Asteroids & Meteroids
Comets
Inner Planets
The inner four rocky planets
at the center of the solar
system are:
Mercury
Venus
Earth
Mars
Mercury
Planet nearest the sun
Second smallest planet
Covered with craters
Has no moons or rings
About size of Earth’
Earth’s moon
Venus
Sister planet to Earth
Has no moons or rings
Hot, thick atmosphere
Brightest object in sky besides sun and
moon (looks like bright star)
Covered with craters, volcanoes, and
mountains
Earth
Third planet from sun
Only planet known to have life and
liquid water
Atmosphere composed of Nitrogen
(78%), Oxygen (21%), and other gases
(1%).
Mars
Fourth planet from sun
Appears as bright reddish color in the
night sky
Surface features volcanoes and huge
dust storms
Has 2 moons: Phobos and Deimos
Asteroid Belt
Separates the inner, terrestrial planets
from the outer, Jovian planets
Contains ~100,000 asteroids.
Largest known asteroid: 4 Vesta
Largest object : Ceres (dwarf planet)
Outer Planets
The outer planets composed
of gas are :
Jupiter
Saturn
Uranus
Neptune
Jupiter
Largest planet in solar system
Brightest planet in sky
At last count, 65 moons: 5 visible from
Earth
Strong magnetic field
Giant red spot
Rings have 3 parts: Halo Ring, Main
Ring, Gossamer Ring
Saturn
6th planet from sun
Beautiful set of rings
62 moons
Largest moon, Titan,
Easily visible in the night
sky
Voyager explored Saturn
and its rings.
Uranus
7th planet from sun
Has a faint ring system
27 known moons
Covered with clouds
Uranus sits on its side with the north
and south poles sticking out the
sides.
Neptune
8th planet from sun
Discovered through math
12 known moons
Triton largest moon
Great Dark Spot thought to be a
hole, similar to the hole in the
ozone layer on Earth
A Dwarf Planet
Pluto is a small solid icy
planet is smaller than the
Earth's Moon.
Pluto
Never visited by
spacecraft
Orbits very slowly
Charon,
Charon, its moon, is
very close to Pluto
and about the same
size
Two Types of Planets: Terrestrial and Jovian
Why?
What does the solar system look like
from far away?
•
Sun, a star, at the center
•
Inner (rocky) Planets
(Mercury, Venus, Earth,
Mars) ~ 1 AU
•
Asteroid Belt ~ 3 AU
•
Outer (gaseous) Planets
(Jupiter, Saturn, Neptune,
Uranus) ~ 5-40 AU
•
Kuiper Belt ~ 30 to 50 AU
-includes Pluto
•
Oort Cloud ~ 50,000 AU
Bode’s Law
•A rough rule that predicts the spacing of the planets in the Solar System
•To find the mean distances of the planets, beginning with the following simple sequence of
numbers:
0 3 6 12 24 48 96 192 384
•With the exception of the first two, the others are simple twice the value of the preceding
number.
•Add 4 to each number:
4 7 10 16 28 52 100 196 388
•Then divide by 10:
0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 38.8
Planet
Actual Distance (AU)
Bode’
Bode’s Law
Mercury
0.39
0.4
Venus
0.72
0.7
Earth
1.00
1.0
Mars
1.52
1.6
Jupiter
5.20
5.2
Saturn
9.54
10.0
Uranus
19.2
19.6
Neptune
30.1
38.8
Works for
moons
too!
Asteroids
Small bodies
Believed to be left over
from the beginning of
the solar system
billions of years ago
100,000 asteroids lie in
belt between Mars and
Jupiter
Largest asteroids have
been given names
Where are the asteroids?
Most asteroids are
located in two regions:
•Asteroid belt
•Orbit of Jupiter… the
Hildas (the orange
"triangle" just inside the
orbit of Jupiter) and the
Jovian Trojans (green).
The group that leads
Jupiter are called the
"Greeks" and the trailing
group are called the
"Trojans"
Comets
Small icy bodies
Travel past the Sun
Give off gas and dust as
they pass by
Anatomy of a Comet
Where are the comets?
Kuiper Belt
A large body of small
objects orbiting (the short
period comets <200 years)
the Sun in a radial zone
extending outward from the
orbit of Neptune (30 AU) to
about 100 AU. Pluto maybe
the biggest of the Kuiper
Belt object.
Oort Cloud
Long Period Comets
(period > 200 years) seems
to come mostly from a
spherical region at about
50,000 AU from the Sun.
Key Ideas
Properties of the Planets: All of the planets orbit the
Sun in the same direction and in almost the same plane.
Most of the planets have nearly circular orbits.
The four inner planets are called terrestrial planets. They
are relatively small (with diameters of 5000 to 13,000
km), have high average densities (4000 to 5500 kg/m3),
and are composed primarily of rocky materials.
The four giant outer planets are called Jovian planets.
They have large diameters (50,000 to 143,000 km) and
low average densities (700 to 1700 kg/m3) and are
composed primarily of light elements such as hydrogen
and helium.
Key Ideas
Satellites and Small Bodies in the Solar System:
Besides the planets, the solar system includes satellites
of the planets, asteroids, comets, and trans-Neptunian
objects.
Seven large planetary satellites (one of which is our
Moon) are comparable in size to the planet Mercury. The
remaining satellites of the solar system are much
smaller.
Key Ideas
Asteroids are small, rocky objects, while comets and
trans-Neptunian objects are made of ice and rock. All are
remnants left over from the formation of the planets.
Most asteroids are found in the asteroid belt between the
orbits of Mars and Jupiter, and most trans-Neptunian
objects lie in the Kuiper belt outside the orbit of Neptune.
Pluto is one of the largest members of the Kuiper belt.
Key Ideas
Spectroscopy and the Composition of the Planets:
Spectroscopy, the study of spectra, provides information
about the chemical composition of objects in the solar
system.
The spectrum of a planet or satellite with an atmosphere
reveals the atmosphere’s composition. If there is no
atmosphere, the spectrum indicates the composition of
the surface.
The substances that make up the planets can be
classified as gases, ices, or rock, depending on the
temperatures at which they solidify.
Key Ideas
Impact Craters: When an asteroid, comet, or meteoroid
collides with the surface of a terrestrial planet or satellite,
the result is an impact crater.
Geologic activity renews the surface and erases craters,
so a terrestrial world with extensive cratering has an old
surface and little or no geologic activity.
Because geologic activity is powered by internal heat,
and smaller worlds lose heat more rapidly, as a general
rule smaller terrestrial worlds are more extensively
cratered.
Key Ideas
Magnetic Fields and Planetary Interiors: Planetary
magnetic fields are produced by the motion of electrically
conducting liquids inside the planet. This mechanism is
called a dynamo. If a planet has no magnetic field, that is
evidence that there is little such liquid material in the
planet’s interior or that the liquid is not in a state of
motion.
The magnetic fields of terrestrial planets are produced by
metals such as iron in the liquid state. The stronger fields
of the Jovian planets are generated by liquid metallic
hydrogen or by water with ionized molecules dissolved in
it.