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Unit 3 Lesson 6 Small Bodies in the Solar System
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Unit 3 Lesson 6 Small Bodies in the Solar System
Florida Benchmarks
• SC.8.N.1.1 Define a problem from the eighth
grade curriculum using appropriate reference
materials to support scientific understanding, plan
and carry out scientific investigations of various
types, such as systematic observations or
experiments, identify variables, collect and
organize data, interpret data in charts, tables, and
graphics, analyze information, make predictions,
and defend conclusions.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Florida Benchmarks
• SC.8.E.5.3 Distinguish the hierarchical
relationships between planets and other
astronomical bodies relative to solar system,
galaxy, and universe, including distance, size, and
composition.
• SC.8.E.5.7 Compare and contrast the properties
of objects in the Solar System including the Sun,
planets, and moons to those of Earth, such as
gravitational force, distance from the Sun, speed,
movement, temperature, and atmospheric
conditions.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Florida Benchmarks
• LA.6.2.2.3 The student will organize information
to show understanding (e.g., representing main
ideas within text through charting, mapping,
paraphrasing, summarizing, or
comparing/contrasting).
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Unit 3 Lesson 6 Small Bodies in the Solar System
Bigger Is not better
Where are small bodies in the solar
system?
• Scientists estimate that there are up to a trillion
small bodies in the solar system. They lack
atmospheres and have weak surface gravity.
 The largest of the small bodies, the dwarf
planets, are found in regions known as the
asteroid belt and Kuiper belt.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Where are small bodies in the solar
system?
 The Kuiper belt is located beyond the orbit of
Neptune. It contains Kuiper belt objects and
comets.
• Comets are also located in the Oort cloud, which
is a region that surrounds the solar system and
extends almost halfway to the nearest star.
• Two other types of small bodies, asteroids and
meteoroids, are located mostly between the orbits
of Venus and Neptune.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What are dwarf planets?
 A dwarf planet is a celestial body that orbits the
sun and is round because of its own gravity.
 A dwarf planet does not have the mass to have
cleared other bodies out of its orbit around the
sun.
• Five dwarf planets have been identified: Ceres,
Pluto, Eris, Haumea, and Makemake.
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Unit 3 Lesson 6 Small Bodies in the Solar System
KBOs
What are Kuiper belt objects?
 The Kuiper belt is a region of the solar system
that begins just beyond the orbit of Neptune.
• The Kuiper belt extends outward to about twice
the orbit of Neptune, a distance of about 55
astronomical units (AU).
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Unit 3 Lesson 6 Small Bodies in the Solar System
What are Kuiper Belt objects?
 A Kuiper belt object (KBO) is any of the minor
bodies in the Kuiper belt. They are made of
methane ice, ammonia ice, and water ice.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Pluto: From Planet to KBO
• Until 2006, Pluto was considered to be the ninth
planet in the solar system.
• Beginning in 1992, Kuiper belt objects began to be
discovered beyond Neptune’s orbit, some of which
had similar size and composition as Pluto.
• In 2006, Pluto was redefined as a “dwarf planet”
by the International Astronomical Union.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Pluto: From Planet to KBO
• Many large KBOs have satellites.
• Pluto, the second-largest KBO, has Charon as its
largest satellite.
• Some KBOs and their satellites, such as Pluto and
Charon, orbit each other.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about comets?
 A comet is a small body of ice, rock, and dust
that follows a highly elliptical orbit around the
sun.
 All comets have a nucleus that is composed of ice
and rock.
• Most comet nuclei are between 1 km and 10 km
in diameter.
• If a comet approaches the sun, solar radiation and
heating cause the comet’s ice to change to gas.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about comets?
 A coma is a spherical cloud of gas and dust that
comes off the nucleus.
 The ion tail of a comet is gas that has been
ionized by the sun. This ion tail always points
away from the sun.
• A second tail made of dust and gas curves
backward along the comet’s orbit. This dust tail
can be millions kilometers long.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about comets?
 The Oort cloud is a spherical region that
surrounds the solar system.
• Comets can form in the Oort cloud when two
objects collide, or when the gravity of a nearby
star sends an object into the inner solar system.
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Unit 3 Lesson 6 Small Bodies in the Solar System
On the Rocks
What do we know about asteroids?
 An asteroid is a small, irregularly shaped, rocky
object that orbits the sun.
 Most asteroids are located in the asteroid belt
between the orbits of Mars and Jupiter.
• The asteroid belt contains hundreds of thousands
of asteroids, called main-belt asteroids.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about asteroids?
 The composition of asteroids varies.
Hydrocarbons are materials that are found in
asteroids.
• Some are rich in carbon.
• Others are rocky, with cores of iron and nickel.
• Some have a rocky core surrounded largely by
ice.
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Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about asteroids?
• Some asteroids appear to be piles of rock loosely
held together.
• Others contain economic minerals such as gold,
iron, nickel, cobalt, and platinum.
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Unit 3 Lesson 6 Small Bodies in the Solar System
Burned Out
What do we know about meteoroids,
meteors, and meteorites?
 A sand grain- to boulder-sized rocky body that
travels through space is a meteoroid.
 A bright streak of light that results when a
meteoroid burns up in Earth’s atmosphere is
called a meteor.
 A meteorite is a meteoroid that reaches Earth’s
surface without burning up.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 6 Small Bodies in the Solar System
What do we know about meteoroids,
meteors, and meteorites?
 Meteoroids that burn up in the atmosphere that
are close enough to see are often referred to as
shooting stars.
• Meteoroids come from the asteroid belt, Mars, the
moon, and comets.
• Most meteoroids that enter Earth’s atmosphere do
not reach Earth’s surface. Many explode in the
upper atmosphere; others skip back into space.
• Large meteoroids that enter Earth’s lower
atmosphere or strike Earth’s surface can be
destructive.
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