Download The Moon

Classifying objects in our Solar System
 What does the word category mean?
 A group of things or objects that have something in
common with each other.
 What are some ways that you sorted your cards
yesterday?
 Were your sorts scientific?
 There are many diverse objects in the Solar System.
 What makes an object a planet?
 Discuss
 Look at your cards. How many in the set are stars?
 One!
 Remember the Solar System is centered around
the Sun. This is the only STAR in our Solar System.
 First thing, find the Sun and set it aside. It is it’s own
category.
 Next:
 Planet
 Not a planet
 Don’t know/Not sure
 Put the cards for each category in that spot.
 Remember, you need a REASON for your sort. Talk at
your table and make a decision.
 Some groups can share their sorts. 
 I knew it was a planet.
 It looks round/spherical.
 It looks about the right size.
 It looks like it has an atmosphere.
 It orbits the sun.
 Size
 Spherical shape.
 Did the cards tell us this???
 Is it difficult to determine what is a planet and what is not?
 Um.. Yes...
 Find #23 and #26.
 How are these similar and different?
 Similar shape, but different sizes.
 Did anyone think these were planets?
 These are NOT planets even though they orbit the
Sun.
 #23 is Ida, an asteroid. It orbits the Sun in the asteroid
belt between Mars and Jupiter. Asteroids are small,
rocky objects that orbit the Sun. The Asteroid Belt is a
collection of many multi-sized chunks that orbit the
Sun.
 #26 is the nucleus of Comet Borrelly.
 Like asteroids, comets orbit the sun. Their orbit is elipitical.
 The nucleus of a comet is often referred to as a “dirty
snowball” because it is a mixture of ice, gas and rocky dust.
 When comets get closer to the sun, the ice will vaporize, a
coma or glowing cloud will form around the nucleus.
 When comets get closer to the sun, they will have tails that
trail behind them. Most comets are not close enough to the
sun to have tails.
 Most comets are thought to have originated in either the
Kuiper Belt or the Ort Cloud.
 A full comet with a coma and a tail?
 #32 is Comet Hale-Bopp. This is one of the brightest comets
of the 20th century.
 A comet that has broken into 2 pieces?
 Do you remember comet Shoemaker-Levy? The fragments
were observed crashing into Jupiter in 1993.
 Find #9
 This is the nucleus of Comet Halley, one of the most famous.
Orbit takes 76 years.
 Find #21 and #29
 These are both comet nuclei.
Start a new sub category of “Not a Planet” for the comets.
 #24 and #33
 Both are asteroids that are not part of the asteroid belt.
 Both of their orbits carry them close to Earth’s orbit.
 There have been space probe missions to both of these
asteroids.
 Start an asteroid pile under the not a planet category.
 #31
 Dactyl
 Orbits the asteroid Ida. (Crazy, right?)
 First moon ever discovered of an asteroid.
 Discuss at your table. Is it a moon or an asteroid?
 Remember, even though they orbit the Sun, asteroids are




not planets.
Place #31 where you think it should go.
Sort the remaining comet and asteroid cards.
Comets: 9, 21, 26, 29, 30, 32
Asteroids: 12, 23. 24, 31, 33
 Find #8 and #11
 These are both similar in size and appearance but one
is a planet and one is a moon.
 What would you need to know to determine which one
was a planet and which one was a moon?
 We would need to know what they orbit.
 #8 is Mercury and #11 is Callisto, a moon of Jupiter.
 Place these in the correct piles.
 Moons also orbit the Sun as well.
 They orbit with their planet.
 #10, Ganymede
 #12, Io
 #13 Europa
 #11, Callisto
 All of these are moons of Jupiter.
 Place them in the not a planet category along with all
the other moons.
 Find #4 and #14.
 Both have cloudy atmospheres.
 One is Venus and one is Titan the largest moon of
Saturn.
 #4 is Venus. Titan is much smaller.
 Place these in the correct piles.
 So is an atmosphere an criteria for being a planet?
 Nope!
 Some moons have an atmosphere and some planets
have hardly any like Mercury.
 After we have discussed and deleted some stuff off the list,
here is what is left:
 Large, spherical and orbits the Sun.
 What cards would you pick that fits this criteria?








#8, Mercury
#4, Venus
#1 Earth
#6, Mars
#5, Jupiter
#7, Saturn
#16, Uranus
#18, Neptune












Moons orbit planets.
#3 The Moon, orbits Earth
#10 Ganymede, orbits Jupiter
#11 Callisto, orbits Jupiter
#12 Io, orbits Jupiter
#13 Europa, orbits Jupiter
#14 Titan, orbits Saturn
#15 Tethys, orbits Saturn
#19 Triton, orbits Neptune
#20 Ariel, orbits Uranus
#22 Phobos, orbits Mars
#25 orbits Saturn
 Pluto has long been considered a planet.
 However, in 2006, the International Astronomical
Union voted on a resolution to set new criteria for an
object in the solar system to be considered a planet.
 Orbits the Sun
 It is large enough that gravity pulls it into the shape of a
sphere.
 It has cleared the neighborhood around its orbit.
 Pluto did not meet the third and was demoted and is
now called a dwarf planet.
 Find #17, #27, #28 and #35.
 Discuss at your tables all the ways that these objects are similar




to each other.
Some astronomers think these objects should be classified as
planets. Do you think any of them should be? Which objects?
#17 is Ceres, an asteroid. Astronomers do not consider it a planet
because it is too small.
#27 is Pluto and #28 is Charon, a moon od Pluto. Charon is not a
planet because it is smaller than Pluto and orbits Pluto.
#28 is Eris. It is similar to Pluto but slightly larger than Pluto.
Eris is the largest known object in a collection of objects beyond
Neptune called the Kuiper Belt. Like the asteroid belt, the Kuiper
Belt is composed of multi-sized objects. Pluto is considered to be
a Kuiper Belt object or KBO, like Eris.
 Discuss at your table. Is Pluto a planet or a KBO?
 Astronomers categorize objects using certain
characteristics.
 The objects we looked at today can be categorized in many
different ways depending on what characteristics you
choose to look at.
 Astronomers use a certain criteria to classify objects in our
solar system.





Shape
Appearance
What they orbit
Size
Distance from the Sun
 Remember, not all objects can be easily categorized!