1. Warm Up Questions Which planet is bigger, Mercury or Jupiter ?
Are the gas giant planets closer to the Sun than the rocky planets (yes/no)?
How many planets are in the Solar System?
Is the Sun bigger, smaller, or the same size as the Moon?
What is the difference between the Solar System and the Milky Way Galaxy (just one sentence) ?
These are here because in theory, you’ve given the questions to the students before class to answer. Alternatively, you can hand out the questions at the start of class and go over the answers after the students are done. The idea for giving warm up questions is identify what the students know, what they don’t know, and where their misconceptions are.

2. Solar System = Sun, 8-planets (their 166 known moons), dwarf planets (to be defined next class), and small Solar System bodies (e.g., comets and asteroids). All of these celestial objects are bound to the Sun by gravity and formed 4.6 billion years ago. 2

3. Why are there only 8 planets now?
Three types of objects orbit our Sun:
Planets
Dwarf Planets
Plutoids
Small solar system bodies

4. What is a planet?
In August of 2007 the International Astronomical Union redefined what a planet is (no official scientific definition of a "planet" existed before). A planet:
Is a body that orbits the Sun (this definition only applies to our Solar System)
Is large enough for its own gravity to make it round
And has "cleared its neighborhood" of smaller objects
So a new the category of dwarf planet was created, which currently includes Pluto, Eris*, Haumea, Makemake and and Ceres**.
*Eris is the largest known dwarf planet in the Solar System and the ninth largest body known to orbit the Sun. Its distance from the Sun is 97 AU.
**Ceres is the smallest identified dwarf planet in the Solar System and, because it’s the largest asteroid, the only dwarf planet in the asteroid belt.

5. What is meant by “cleared its neighborhood of smaller objects”?
Kuiper belt, is a region of the Solar System extending from the orbit of Neptune (30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger-20 times as wide and times as massive. Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water.
Pluto’s orbit is very elliptical (29-49 AU). When Pluto is outside the orbit of Neptune (30 AU) it enters the Kuiper belt, which is comprise of icy objects some of which are smaller and some actually bigger than Pluto. 5 5

6. What is a Dwarf Planet? Celestial body orbiting the Sun
Massive enough to be rounded by its own gravity
BUT has NOT cleared its neighboring region of planetesimals
Is not a satellite
A plutoid is a dwarf planet beyond the orbit of Neptune

7. Only 5 Dwarf Planets recognized so far but there may be more than 200
Pluto, approximate
true color
Makemake,
(Artist’s conception)
Ceres, seen through
(Hubble telescope)
Eris, seen through
(Hubble telescope)
Ask student to identify which dwarf planets are plutoids
Haumea, with its 2 moons,
Hi‘iaka and Namaka
(Artist’s conception)

8. Pacific Island Names for Dwarf Planets
Haumea is the Hawaiian goddess of childbirth and fertility.
The the moons "Hiʻiaka" and "Namaka” are named after after two of Haumea's daughters.
NOTE: Although Haumea is not spherical, it is considered a dwarf planet because it is in hydrostatic equilibrium: its ellipsoidal shape is the equilibrium state resulting from the object's rapid rotation (in much the same way as a water balloon stretches out when tossed) and not due to insufficient self-gravity.

9. Pacific Island Names for Dwarf Planets
Makemake is the creator of humanity in the mythos of the Rapanui, the native people of Easter Island. The name choice preserves the planetary object's connection with Easter Island.

10. What are Small Solar System Bodies?
Neither a planet nor a dwarf planet
All other objects orbiting the Sun
All minor planets except dwarf planets
Asteroids (except Ceres, the largest asteroid)
Comets
The bodies are not massive enough to be rounded by their own gravity 10 10

11. Characteristics of Terrestrial and Gas Giant Planets
Terrestrial Planets
Gas Giant (Jovian) Planets
Mercury, Venus, Earth, Mars
Rocky
More dense
Smaller
More closely spaced
Closer to the Sun
Jupiter, Saturn, Uranus, Neptune
Gaseous, made of hydrogen and helium
Less dense (Saturn would float)
Larger
Spaced farther apart
Farther from the Sun
NOTES: He = helium; H = hydrogen

12. Terrestrial Planets Venus Mercury Moon Mars
Earth is the largest Terrestrial planet
Venus is 95% the size of Earth
Mars is 53% the size of Earth
Mercury is 38% the size of Earth
The Moon is 25% the size of Earth
Moon
Mars

13. Gas Giants Uranus Jupiter Neptune Saturn Earth to scale
Earth is dwarfed by the gas giant planets
Jupiter is 11.2 times bigger than Earth (I round it off to 10 times bigger)
Saturn is 9.5 times bigger than Earth
Uranus is 3.92 times bigger than Earth
Neptune is 3.89 times bigger than Earth
Saturn

14. Surface Temperature on Planetary Objects
Error bars show the range in temperature for an object
Mercury experiences the biggest temperature range (700oF to -300oF)
See extra sides at the end
Do you see patterns or anomalies in the data?

15. Length of day on planetary objects
Pattern: Most planets spin in the same direction (from east to west). Exceptions are Venus and Pluto, and Uranus which orbits on its side.
Pattern: Gas giants have shorter days than terrestrial planets (probably because they are larger)
Mercury has the longest day at 176 Earth days to one Mercury day
Mars has a length of day most similar to Earth’s at 24 and 40 minutes
Jupiter has the shortest day (10 hours)
One day on the Moon is 29.5 Earth days (I’d like to take a week holiday on the Moon, it would last ~150 Earth days!)
Do you see patterns or anomalies in the data? 15

16. Planetary Density
Do you see patterns or anomalies in the data?

17. The Milky Way Galaxy 100,000 light years across
1,000 light years thick
200 billion stars
The Milky Way Galaxy may have between 200 & 400 billion stars
As a guide to the relative physical scale of the Milky Way, if it were reduced to 130 km (80 mi) in diameter, the Solar System would be a mere 2 mm (0.08 inches) in width.
The Andromeda Galaxy, also a spiral galaxy, is the nearest spiral galaxy to our own, the Milky Way, at approximately 2.5 million light-years away.
You are here

18. Extra Slides

19. Universe = All matter, all stars, all planets.
The Big Bang created the Universe 13.7 billion years ago. Composition of the Universe at this time was mostly hydrogen and some helium.

20. The Milky Way Galaxy
A galaxy, is a grouping of billions of stars. There are about billion stars in our galaxy, the Milky Way Galaxy.
The Milky Way is ~100,000 light year across and about 1,000 light years thick.
The Milky Way Galaxy may have between 200 & 400 billion stars
As a guide to the relative physical scale of the Milky Way, if it were reduced to 260 km (160 mi) in diameter (distance between Kauai and Big Island), the Solar System would be a mere 4 mm (0.16 inches) in width.
The Andromeda Galaxy, also a spiral galaxy, is the nearest spiral galaxy to our own, the Milky Way, at approximately 2.5 million light-years away.
The closest star system that we know of is Alpha Centauri, located about 4.37 light years away (41.5 trillion km). The system easy to see with the unaided eye – if you live in the Southern hemisphere. In fact, Alpha Centauri is the 4th brightest star in the star in the sky.
The Andromeda Galaxy, also a spiral galaxy, is the nearest spiral galaxy to our own, the Milky Way, at approximately 2.5 million light-years away.
Milky way viewed edge on from Earth 20

21. The Milky Way Galaxy
The Sun and the planets are part of the Milky Way galaxy. Located in one of the arms, our Solar System revolves about the center of the galaxy at a speed of over 200 km per second. Yet the galaxy is so vast that it takes about 250 million years to complete one revolution! The Sun has yet to complete its nineteenth orbit about the galactic center.
You are here 21

22. Is the Andromeda Galaxy within the Milky Way Galaxy?
Yes, it definitely is!
I think it is but I’m not sure.
I don’t think it is but I’m not sure
No, it definitely is not!
I don’t know how to determine whether it’s inside or outside our galaxy

23. Planet Masses
Do you see patterns or anomalies in the data?

24. Temperatures In the Solar System
Mercury exhibits the largest variation in temperature of any body in the Solar System (-330 to 750oF*) because it has no atmosphere.
The Moon also has large but less extreme temperature variations (-230 to 240oF*) for the same reason.
Atmospheres are like blankets that insulate a planet from extreme temperature swings.
MESSENGER image of Mercury
*Temperature minimum and maximum are for night time and day time temperatures.

25. Temperatures In the Solar System
Venus has the highest temperature of any planet in the Solar System at 864oF! Hot enough to melt lead. Yikes!
Its temperature does not vary from day to night like Mercury, Earth, the Moon and Mars because its atmosphere is
Thick and dense
Effective at trapping the Sun’s heat
Venus Express image of Venus

26. Temperatures In the Solar System
Earth’s average (57.5oF) temperature is just right
Not too hot to evaporate all its water away
Not too cold to freeze all its water and keep it ice
Temperature extremes are also minor relative to Mercury and the Moon (average min 40o and max 75oF)
Earth’s atmosphere from the international Space Station

27. Temperatures In the Solar System
Mars’ average (-50oF), so any water is frozen solid
Mars has a thin atmosphere (1% that of Earth) so it does moderate the temperature some.
Maximum temperature is close to Earth’s average low (20oF) but the low on Mars is very cold (-120oF)
Mars' thin atmosphere, visible on the horizon in this low orbit image

28. Do all planet in our Solar System orbit the Sun in the same direction?
Yes, they orbit in the same direction
Maybe
I don’t think they do
No, they don’t orbit in the same direction
I’ve never thought about that before

29. Planetary Orbit Direction
All planets orbit the Sun in the same direction: counterclockwise.

30. Do all planets have the same length of year (e.g. 365.25 Earth days)?
Yes No
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Orbital period (Earth years)
0.24
0.62 1
1.88
11.86
29.46
84.01
164.8
247.7
Where a year equals one trip around the Sun

31. Orbital Velocity
Orbital velocity varies systematically with distance from the Sun

32. Gravity and Radius of the Planets