Content Benchmark E.8.B.2
Students know the solar system includes a great variety of planetary moons, asteroids, and
comets. I/S
Mankind has been intrigued by the cosmos, perhaps since we were first capable of cognitive
thought. As we’ve gazed upon the night sky, our imaginations have run wild. We have seen
mystical beings in the patterns of stars (Figure 1) and attributed to them powers and control over
our daily lives and future destinies (think astrology, horoscopes and the Zodiac)
(http://www.windows.ucar.edu/tour/link=/mythology/stars.html&edu=mid) and,
(http://home.comcast.net/~chris.s/myth.html).
Figure 1. Leo the Lion
(From http://www.astrologyweekly.com/zodiac-pictures/zodiac-constellation-pictures.php)
We observed that some stars seemed to wander across the sky. These wandering stars (planets)
found places both in Greek and Roman mythology as gods and goddesses
(http://www.kidscosmos.org/kid-stuff/planet-lore.html). The appearance of comets was a source
of terror to our ancestors, as comets were thought to foreshadow disaster
(http://pioneer.chula.ac.th/~crabtree/readsup9.1.htm). Figure 2 is from the 11th century Bayeux
Tapestry which appeared in the sky during the battle of Hastings. England was conquered by the
French army, and King Harold II died in the battle.
Figure 2. Depiction of comets as an evil omen
(From http://ircamera.as.arizona.edu/NatSci102/NatSci102/text/comethalley.htm)
Earth’s closest celestial body has spurred our dreams and mind’s eye, as well. Who didn’t grow
up looking for the Man in the Moon (Figure 3)? Which of us didn’t long for a taste of the
Moon’s green cheese? And how did the cow manage to jump over the Moon?
Figure 3. The Man in the Moon from Le Voyage Dans La Lune
(From http://boingboing.net/images/Le_Voyage_dans_la_lune.jpg)
Students are taught at a young age that the planets orbit our sun, and that the Moon orbits Earth.
Our moon is the most obvious non-planetary satellite, easily visible to the naked eye. Comets
are likely the second solar object recognized not as a planet, but still as an object which orbits the
sun. Edmund Halley, in 1705, calculated the orbit of what he believed to be the same comet
which had visited previously in 1531, 1607, and 1682. His calculations were supported when the
comet (now his namesake) reappeared in 1758 (http://www.rasc.ca/comets/index.shtml). In the
1950s, Jan Oort and Gerald Kuiper postulated two primary sources for comets, the Oort Cloud
which is found as a spherical cloud surrounding our solar system,
(http://www6.uniovi.es/solar/eng/oort.htm) and (http://oort.com/) and the Kuiper Belt, which
exists as a disk within the plane of the ecliptic, just beyond Neptune’s orbit
(http://www.solarviews.com/eng/kuiper.htm) (Figure 4).
Figure 4. The Oort Cloud and Kuiper Belt
( From http://www.solarviews.com/browse/comet/kuiper3.jpg)
Many people have seen meteors (shooting stars), but it took longer to correlate Earth’s periodic
meteor showers with comets. The Workshop on Dust in Planetary Systems 2005 reported, “The
idea that the fragmentation of comets is a source of meteoroids causing meteor showers on Earth
was first proposed following the 1872 and 1885 Andromedid storms, which followed the
breakup of lost comet 3D/Biela in 1832, and the continued fragmentation of the comet observed
in the returns of 1846 and 1852.” (http://www.lpi.usra.edu/meetings/dust2005/pdf/4032.pdf).
While periodic meteor showers were found to correspond with current and old cometary orbits,
there have occurred meteor strikes on Earth which did not originate in conjunction with comets.
Asteroids, the source for these other meteors, were discovered in 1801 by Giuseppe Piazzi,
though neither he nor his contemporaries would realize the relationship. Piazzi was searching
the region of space between the orbits of Mars and Jupiter (Figure 5), in the general area
predicted by the Titus-Bode Law (purported by early astronomers to calculate planetary
distances from the Sun) to hold a yet undiscovered planet.
Figure 5. Location of Asteroid Belt
(From http://www.solarviews.com/eng/asteroid.htm)
Initially, Piazzi thought he had discovered a comet, but upon analyzing its orbit, realized it did
behave more like a planet than a comet in its path of revolution about the Sun. He named this
first asteroid, the largest ever cataloged, Ceres (http://www.britannica.com/eb/article-9110155).
A few more asteroids were detected in the years after Piazzi’s discovery, and by the end of the
19th century, a few hundred asteroids had been located. It has been calculated that the combined
mass of all the asteroids is less than that of Earth’s moon
(http://seds.org/nineplanets/nineplanets/asteroids.html). Once astronomers understood that the
asteroid belt contributes heavily to the meteorites impacting Earth, they began detailed studies of
the orbital paths of the asteroids, paying particular attention to asteroids whose orbits bring them
very close to Earth (Near Earth Asteroids) (http://www.jpl.nasa.gov/releases/2000/neat.html). Of
particular concern is Apophis, an asteroid which, on April 13, 2029, will pass by Earth at a
distance of 22,000 miles (just beneath the level of Earth’s high-altitude artificial satellites)
(http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2494
&mode=thread&order=0&thold=0). If Apophis were to impact the Earth, it would likely have
results similar to or exceeding the impact event which resulted in the extinction of dinosaurs.
The meteorites which strike Earth are derived primarily from comets or asteroids, but some have
origins from our Moon and from Mars. These latter meteorites are believed to have been blasted,
respectively, from the crust of the Moon and the crust of Mars when those solar bodies were
themselves impacted by meteorites. Characteristics of all the types of meteorites which have
been found on Earth are described at the following web site
http://www.nineplanets.org/meteorites.html
Earth has a moon. We’ve know this since humans first watched the night (and even daytime)
sky. But do other planets have moons? The answer is yes! Interestingly, the first moons
orbiting a planet other than Earth were discovered not on the planet nearest Earth with moons
(Mars) but on Jupiter, a planet almost eight times as far from Earth as is Mars. In 1610, Galileo
was studying Jupiter through his telescope. Over a period of several weeks, he realized what had
appeared to be stars nearby Jupiter (which kept changing their positions) were actually bodies in
orbit about Jupiter. These are the Galilean moons knows as Io, Europa, Ganymede and Callisto
for more information visit http://www2.jpl.nasa.gov/galileo/ganymede/discovery.html.
As telescopes have improved, and as we have sent exploratory satellites to visit the planets in our
solar system, we have discovered that the only planets without moons are Mercury and Venus.
Earth has one moon, Mars has two, the Jovian planets all have several moons, and Pluto (if you
still elect to call this recently demoted solar body a planet) has three known moons.
More information on the moons of these planets can be found using the followings URLs:
http://www.nineplanets.org/
http://www.astronomy.com/asy/default.aspx?c=a&id=2220
http://spaceplace.nasa.gov/en/kids/sse_flipflop2.shtml
It should be noted that another category of object found in orbit around planets are “rings.”
Rings have been discovered around Jupiter, Saturn, Uranus and Neptune. They appear to have
formed from different causes, but all are found within that planet’s Roche Limit (see #4 under
Intervention Strategies and Resources for an explanation of the Roche Limit). The rings
themselves are small bodies made of dust, rock and ices found in sequences of orbital disks
around those planets (http://astroprofspage.com/archives/476). Specific information on the rings
of the Jovian planets follow:
Jupiter http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Rings
Saturn http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn&Display=Rings
Uranus http://solarsystem.nasa.gov/planets/profile.cfm?Object=Uranus&Display=Rings
Neptune http://solarsystem.nasa.gov/planets/profile.cfm?Object=Neptune&Display=Rings
Content Benchmark E.8.B.2
Students know the solar system includes a great variety of planetary moons, asteroids, and
comets. I/S
Common misconceptions associated with this benchmark
The following misconceptions were listed on the website for Amazing Space – Myths vs
Realities for the Solar System which can be accessed at
http://amazingspace.stsci.edu/resources/myths/solar_system.php.p=Teaching+tools%40%2Ceds%2Ctools%2C
%3EMyths+vs.+realities%40%2Ceds%2Ctools%2Ctype%2Cmyths.php%3EOverview%3A+Sol
ar+system+myths%40%2Ceds%2Coverviews%2Cmyths%2Csolar_system.php&a=%2Ceds
1. Students incorrectly believe the rings of Saturn are solid disks.
Many photographs of Saturn make it appear that there are a series of solid ring-shaped disks of
differing widths sequenced about Saturn. Unless more closely inspected, students do not
realize that the solid “appearance” is the result of many closely-spaced small fragments. A
simple analogy would be that the picture on a television screen appears to be a smooth, solid
image when seen from a normal viewing distance. But, get right next to the screen and you
can ascertain that the image is made of thousands of discreet pixels.
Further information about planetary rings can be found at http://www.astrotom.com/getting_started/planetary_rings.htm and, http://pds-rings.seti.org/saturn/
2. Students have misconceptions that the solar system is made up of only the Sun and eight
planets.
The primary focus of space education in the early grades is on the Sun, planets, and Earth’s
moon. Some students get the idea that anything else which might be seen in the solar system
entered from outside the solar system. Such a notion is reinforced as people talk of “falling
stars” when referring to meteors.
An excellent resource which covers all the objects in our solar system is the Nine Planets
website, found at http://www.nineplanets.org/
3. Students incorrectly believe comets are composed of the same material as asteroids
Students might learn that both asteroids and comets contribute to the stream of meteors and
meteorites which strike Earth. It may seem logical to them that since meteors are derived from
both asteroids and comets, the composition of asteroids and comets would be the same.
For more information on the composition of asteroids and the composition of comets, visit
http://www.kidscosmos.org/kid-stuff/asteroid-facts.html and,
http://curious.astro.cornell.edu/comets.php
4. Students have difficulty understanding that other stars and galaxies are NOT part of the
solar system
As students star gaze and learn about astronomy, they learn names of constellations while also
being taught how to recognize and name the planets. It is difficult for students to conceive of
the great distances involved, and it is not readily apparent that not only are the stars at different
distances from Earth, so are the planets. So…it seems as though the stars and planets are all
within the same frame of reference, and therefore all part of the solar system.
The Planetary Society provides a good website with additional information regarding the
objects which reside within our solar system
(http://www.planetary.org/explore/topics/groups/our_solar_system/).
Content Benchmark E.8.B.2
Students know the solar system includes a great variety of planetary moons, asteroids, and
comets. I/S
Sample Test Questions
Questions and Answers to follow on a separate document
Content Benchmark E.8.B.2
Students know the solar system includes a great variety of planetary moons, asteroids, and
comets. I/S
Answers to Sample Test Questions
Questions and Answers to follow on a separate document
Content Benchmark E.8.B.2
Students know the solar system includes a great variety of planetary moons, asteroids, and
comets. I/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Views of the Solar System
The website, View of the Solar System, provides detailed descriptions on the origin and
composition of comets. Animations help students understand how comets orbit our Sun and
why they develop tails. Many resources are provided that discuss historic and recent comets.
To access this site, go to http://www.solarviews.com/eng/comet.htm
2. Nine Planets
The Nine Planets website is a wealth of information on the solar system. This particular link
discusses many aspects of asteroids. The composition of asteroids is addressed, as is their
location, their sizes, and historic aspects of asteroids. Photos of various asteroids are included,
and links to other sites on asteroids is provided.
To access this site, go to http://www.nineplanets.org/asteroids.html
3. Moons of the Solar System
Space Today Online has a link (Moons of the Solar System) which is quite detailed in its
description of the moons of each of the planets which have moons (including Earth’s moon).
Information on moons in general is given, and then the moons of the planets are discussed,
with extra, outside links provided with which to obtain more information.
To access this site, go to http://www.spacetoday.org/SolSys/Moons/MoonsSolSys.html
4. Planetary Rings
This website briefly addresses the characteristics of the rings of each of the ringed planets. It
discusses the Roche limit and describes the role of shepherd moons in ring dynamics.
To access this site, go to http://ftp.astronomy.ohio-state.edu/~pogge/Ast161/Unit6/rings.html
5. Planetary Rings Node
This website provides very detailed information on the rings of Jupiter, Saturn, Uranus and
Neptune, each at their specific URL, respectively. Images, animations and links to other sites
are included.
To access the sites related to the Jovian planets, go to
Jupiter (http://pds-rings.seti.org/jupiter/)
Saturn (http://pds-rings.seti.org/saturn/)
Uranus (http://pds-rings.seti.org/uranus/)
Neptune (http://pds-rings.seti.org/neptune/)