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Unit 5: The Solar System
Mr. Ross Brown
Brooklyn School for Law and
Technology
In this unit we will learn about:
• The primary components of the Solar System,
each with unique properties
• The differences between Terrestrial, Jovian,
and dwarf planets
• The ways astronomers measure masses and
radii for bodies in the Solar System and
calculate density
• How the planets formed
• The ways exoplanets are detected
What are the components of the
Solar System?
• 16 November 2015
• Do now: What are the different components
of our Solar System?
The Sun
What are the components of the
Solar System?
• The Sun
• Light and heat generated by nuclear fusion
reactions
• Mass is 700 times all other bodies combined
• 71% Hydrogen, 27% Helium, and small
amounts of all other elements
What are the components of the
Solar System?
• The Terrestrial Planets (Earth-like)
• Mercury, Venus, Earth, Mars
• Small, rocky, thin or no atmosphere
What are the components of the
Solar System?
•
•
•
•
The Jovian Planets (Jupiter-like)
Jupiter, Saturn, Uranus, Neptune
Much larger, gaseous and liquid
Deep, hydrogen rich atmospheres
What are the components of the
Solar System?
• 17 November 2015
• Do now: Beyond Neptune, what do we find
that is still considered within our Solar
System?
What are the components of the
Solar System?
• Many other objects in our Solar System
• Pluto
– Small, ice & rock, tilted orbit, crosses Neptune
– Dwarf planet
– Not so special; Eris is 2x as large, 68 AU
– Plutoids
Pluto’s Orbit
Moons
• Our Moon
• Jupiter has 63, Saturn 61, Uranus 27 and
Neptune 13. Mars has 2. Pluto has 4, Eris 1.
Asteroids
• Asteroids: rocky or metallic bodies
• Ceres is largest, 600 miles across
• Asteroid Belt is between Mars and Jupiter
Kuiper Belt
• 50 AU
• Similar to Asteroid Belt, but objects are made
of ice
• Comets: about 10 km in diameter
– Made of ice, grow tails as they near the Sun
• Further out, Oort Cloud
– Perhaps 100,000 AU
– Comets may originate here
Comets
Comets
Our Solar System
The Eames Brothers
Homework
• 16 November 2015
• Why is Pluto not a planet? What are the three
criteria that determine whether a body is a
planet? Which criterion does Pluto fail to
satisfy?
How do planets move about the
Solar System?
• 23 November 2015
• Do now: How thick is our Solar System (all the
way out to Neptune) if you could look at it
from the side?
How do planets move about the
Solar System?
• Planets arranged along a line in the same plane
• Mercury tilts about 7°
• Counterclockwise orbits (View Earth from
North Pole)
• About as thick as 3 CDs out to Neptune
Mercury’s Orbital Plane
How do planets move about the
Solar System?
• Planets rotate as they orbit, counterclockwise
• Axes are generally perpendicular to orbit
– Uranus tilts almost to orbital plane
– Venus tilts so much it spins “backwards”
• Retrograde, but orbits with other planets
Other Objects
• Asteroids may be tilted but travel in same plane
• Comets travel in any direction
– Could indicate Oort Cloud, rather than ring
• Moons behave similarly
– Orbit planets along equator, with similar tilts
– Large moons may have smaller moons
How are the Planets Spaced
throughout the Solar System?
• Bode’s Law
In what ways are the Inner and
Outer Planets Different?
• 24 November 2015
• Do now: That’s it, in the line above. No, you’re
smart, you can figure it out. The Aim is the Do
Now. OK?
In what ways are the Inner and
Outer Planets Different?
• How can we tell?
– Spectragram
– This can only tell us about atmosphere
• Density analysis (M/V)
– Based on gravitational attraction to another body
• Moon, passing spacecraft
• We can know V=4πR3/3
• R is radius, obtained from angular size and distance
In what ways are the Inner and
Outer Planets Different?
• Compare density
– Earth is 5.5 g/cm3, silicate rock is 3, iron is 8
• Inaccurate
– Jovian planets on average 0.7 to 1.7g/cm3
In what ways are the Inner and
Outer Planets Different?
• Terrestrial Planet Interiors
In what ways are the Inner and
Outer Planets Different?
• Jovian Planet Interiors
In what ways are the Inner and
Outer Planets Different?
In what ways are the Inner and
Outer Planets Different?
How do Planetary Systems Form?
• 30 November 2015
• Do now: Describe our Solar System by listing
basic details: shape, structure of planets,
relationship to the Sun, age.
How do Planetary Systems Form?
• Our Solar System is:
– Flat, with planets orbiting in same direction
– 2 types of bodies: rocky inner planets close to the
Sun, gaseous outer bodies further away
– Outer planets similar in composition to the Sun;
inner planets are like the Sun minus gases that
only condense at low temperatures
– Age of all Solar System bodies less than 4.6 billion
years old.
How do Planetary Systems Form?
• Solar Nebula Theory
– Solar System originated from a flat rotating disk of
gas and dust
– Outer part became planets, inner became the Sun
How do Planetary Systems Form?
• 4.6 BYA: Interstellar Cloud
– Rotating aggregate of gas and dust
How do Planetary Systems Form?
• Solar Nebula
– Interstellar cloud collapse into spinning disk with
most mass in center
How do Planetary Systems Form?
• 2 December 2015
• Do now: You have just met someone who isn’t
in our class. Describe an interstellar cloud so
your new friend understands why interstellar
clouds are important.
How do Planetary Systems Form?
• Condensation of the Nebula
– Gases coolliquidsolid
– Because of differences in condensation
temperature, materials condense at different rates
• Iron, silicates, water
How do Planetary Systems Form?
How do Planetary Systems Form?
• Accretion: tiny particles stick together,
forming bigger particles
• At a certain point, these accretions become
large enough that we consider them
planetesimals (small, planet-like bodies)
How do Planetary Systems Form?
• Planetesimals becoming planets
How do Planetary Systems Form?
• 3 December 2015
• Do now: In what way(s) were the formation of
the terrestrial planets and formation of the
Jovian planets different?
How do Planetary Systems Form?
• Frost line: where Sun’s heat is reduced enough
to have permitted ice to form during early
planet formation. Roughly between Mars and
Jupiter.
How do Planetary Systems Form?
• Planetesimal collisions: with each impact, heat
is generated. Beyond 4 or 5 AU, planetesimal
growth is more rapid; each had more material
from which to grow and ices there added to
silicates and iron.
How do Planetary Systems Form?
• As planets cool, remaining planetesimal
impacts leave craters
– Our Moon, Callisto, etc.
How do Planetary Systems Form?
• Some impacts were greater
– Moon creation
– Venus and Uranus’ rotational axes
– Mercury’s missing crust
How do Planetary Systems Form?
• Some planetesimals didn’t become planets
– Asteroid Belt
– Oort Cloud
– Kuiper Belt
Homework
• 4 December 2015
• Use web resources and identify a recent news
story in space exploration. Write a paragraph
discussing the story and the goals of the
mission. Please include one of the pictures
associate with the story.
What is there beyond our Solar
System?
• 7 December 2015
• Do now: What do you think there is beyond
our Solar System, even beyond the Oort
Cloud? Are there planets with life?
What is there beyond our Solar
System?
• Exoplanets: planets orbiting stars other than
our Sun
• Why?
– Because they’re there!
– And, to learn about our own Solar System
What is there beyond our Solar
System?
What is there beyond our Solar
System?
• How do we detect exoplanets?
– Gravity makes their star “wobble”
– Limitation to this method: planet must be massive
What is there beyond our Solar
System?
• How do we detect exoplanets?
– Transit: exoplanet passes in front of its star
– Limitation to this method: planet and star must align
What is there beyond our Solar
System?
• What helps us detect these exoplanets?
– Kepler space telescope