Download The Solar System: Unit 3 Review/Study Guide

The Solar System: Unit 3 Review/Study Guide
Historical Models of the Solar System: Lesson 1
Geocentric vs. Heliocentric
Parallax – the effect where the position or direction of an object appears to change when
viewed from different positions, especially that of a star viewed from different points in the
earth’s orbit.
Gravity and the Solar System: Lesson 2
Gravity- is a force of attraction between objects that is due to their masses and distances
between them. Objects with greater masses have a greater force of attraction than objects with
lesser masses have. Objects that are close together have a greater force of attraction than
objects that are far apart have. Gravity is the weakest force in nature, yet it is one of the most
important forces in the universe.
Newton’s Law of Universal Gravitation says that the force of gravity:


Increases as the masses of the objects increase
Decreases as the distance between the objects increases
Formation of the Solar System
Step 1: Solar Nebula
Because of gravity, a cloud of
dust and gas collapse, it forms a
rotating protostellar disk
Step 2: The Sun Forms
Temperatures in the
protostellar disk become so hot
that fusion begins and stops the
collapse of matter. This forms
the sun
Step 3: Planetesimals Form
Dust granules form and slowly
increase in size. They collide to
form Planetesimals.
Step 4: Planets Form
Planetesimals collide and form
planets. The rocky, metallic
planets form in the high
temperature inner disk. Planets
with small, rocky cores and
deep gaseous atmospheres
form in the cold outer disk.
OrbitAphelionPerihelionCentripetal Force-
Kepler’s Law’s
1st Law:
Planets Orbits are ELLIPSES.
2nd Law:
In PERIHELION, a planet is in
its point of orbit closest to the
sun. It is also moving at its
fastest speed, because gravity.
In APHELION, a planet is in its
point of orbit farthest from the
sun. It is also moving at its
slowest speed.
3rd Law:
The length of time it takes a
planet to go around the sun is
proportionally related to how
far it is from the sun.
Small Bodies in the Solar System: Lesson 6
Scientists estimate that there are up to a trillion small bodies in the solar system. These
bodies lack atmosphere and have weak surface gravity.
The largest of the small bodies are known as dwarf planets. A dwarf planet is a celestial
body that orbits the sun and is round because of its own gravity, but it does not have the mass
to have cleared other bodies out of its orbit around the sun. There are five known dwarf
planets. One named Ceres is located between Mars and Jupiter in the asteroid belt. The other
four (Pluto, Haumea, Makemake, and Eris) are located in that order in the Kuiper Belt behind
Neptune. The dwarf planets are made of ice and rock. Pluto became a dwarf planet in 2006.
The Kuiper Belt is a region of the solar system that begins just beyond the orbit of
Neptune and contains small bodies made mostly of ice. It extends outward approximately 55
Astronomical Units (AU). The Kuiper Belt is thought to contain matter left over from the
formation of the solar system. This matter formed small bodies instead of planets. A Kuiper Belt
Object is any of the minor bodies in the Kuiper Belt. The first KBO was discovered in 1992. As
more KBO were discovered, including many close to the size of Pluto, it was determined that
Pluto was a Kuiper Belt Object instead of the 9th planet.
Comets! Small bodies of ice, rock, and dust that follow a highly elliptical orbit around the
sun are known as comets. A comet is made of a nucleus (composed of ice and rock), a coma
(the Spherical cloud of gas and dust that comes off of the nucleus), and an ion tail (gas that has
been ionized by the sun). The ion tail only shows up as the comet nears the sun, and it always
points away from the sun. The dust tail of a comet is different from the ion tail, and it can be
millions of km long!
The Oort Cloud is a spherical region that surrounds the solar system and extends almost
halfway to the nearest star. Comets can form in the Oort Cloud when two objects collide.
Comets that form in the Oort Cloud are called long-period comets and can take hundreds of
thousands of years to orbit the sun. Comets can also form in the Kuiper Belt. These comets are
called short-period comets and can take less than 200 years to orbit the sun.
In between Mars and Jupiter is a region known as the asteroid belt. An asteroid is a
small, irregularly shaped, rocky object that orbits the sun. The asteroid belt contains hundreds
of thousands of asteroids. Asteroids can have different compositions. Many have dark surfaces.
Scientists think these are rich in carbon. Other asteroids are thought to be rocky and to have a
core of iron and nickel.
A sand-grain to boulder size rocky body that travels through space is called a meteoroid.
As meteoroids enter Earth’s atmosphere, friction heats them up to thousands of degrees
Celsius. This causes them to glow. Ever see a shooting star? It’s actually a meteoroid burning up
in the Earth’s atmosphere. The bright streak of light that results when a meteoroid burns up in
Earth’s atmosphere is called a meteor. When a meteoroid is large enough to reach Earth’s
surface without burning up completely is called a meteorite. Meteoroids come from the
asteroid belt, Mars, the moon, and comets. Most meteoroids that enter Earth’s atmosphere
never reach Earth’s surface. The ones that do are named for the location they land in.