1. The Ordered Solar System

2. Which planet is bigger, Mercury or Jupiter ?
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.

3. Three types of objects orbit our Sun:
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*, 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. Celestial body orbiting the Sun
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

6. Only 5 Dwarf Planets recognized so far but there may be as many as 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)

7. Pacific Island Names for Planetary Objects
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.

8. Pacific Island Names for Planetary Objects
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.

9. 3. 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)
Comets
Not massive enough to be rounded by its own gravity

10. Terrestrial vs. Gaseous Planets
Jupiter, Saturn, Uranus, Neptune
Gaseous, has more He and H
Less dense (Saturn would float)
Larger
Spaced farther apart
Farther from the Sun
Mercury, Venus, Earth, Mars
Rocky
More dense
Smaller
More closely spaced
Closer to the Sun
NOTES: He = helium; H = hydrogen

11. Terrestrial Planets Mars Venus Mercury
From
This page was copied from Nick Strobel's Astronomy Notes. Go to his site at for the updated and corrected version.
Mars
Venus
Mercury
From Nick Strobel’s Astronomy Notes at

12. Jovian Planets, or Gas Giants
Uranus
Neptune
Saturn
Jupiter
From
This page was copied from Nick Strobel's Astronomy Notes. Go to his site at for the updated and corrected version.
From Nick Strobel’s Astronomy Notes at

13. Do you see patterns or anomalies in these data?
ANSWERS: Students may notice planets in the middle of the solar system have less extreme temperatures and shorter days compared to those closest and farthest from the sun. Venus’ data is very extreme compared to its neighbors. Pluto’s long day also stands out compared to its neighbors.
From

14. On which planet would you weigh the most?
From

15. 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