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Solar System
Excerpt from DSM Solar System Teacher’s Guide, © Copyright by Delta Education, a member of the School Specialty Family.
Not for resale, redistribution, or use other than classroom use without further permission.
G LO S S A RY
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Alpha Centauri A three star system, the closest
to Earth.
aphelion The point along a planet’s orbit at
which it is farthest from the Sun.
asteroid One of millions of very small planets
that orbit the Sun.
asteroid belt The area between the orbits
of Mars and Jupiter where most of the
asteroids in our Solar System are
concentrated.
average distance A measurement used to
calculate the difference in distance between
planets.
axis An imaginary line, or axle, through the
center of an object, about which the object
rotates.
Big Dipper A part of the constellation Ursa
Major, the Great Bear.
Cassiopeia The W-shaped constellation in the
Northern Hemisphere.
centimeter A unit of length equal to one
hundredth of a meter.
Cepheus A constellation near Cassiopeia and
Draco.
circle A closed curved line on which all points
are equidistant from its center.
circumference The length of the closed curve
of a circle.
comet A mass of ice, dust, and rock that orbits
the Sun or a planet.
constellation An area of the sky containing
stars that seem to outline a figure, as
viewed from Earth.
crater The bowl-shaped depression in the
surface of a satellite caused by the impact
of an asteroid or comet.
day The length of time a planet takes to make
one complete rotation about its axis.
diameter The distance from one side of a
circle, through the focus, to the other side.
drawing compass A mechanical device used
to draw circles.
dwarf planet A spherical satellite of a star that
is not massive enough to have cleared the
neighborhood of its orbit.
Earth The third planet from the Sun in our
Solar System.
ellipse A shape like a stretched-out circle;
an oval.
focus (plural: foci) The point at the center of
a circle, or the two points inside an ellipse.
force A push or pull on an object.
friction The force that creates drag on two
substances rubbing together.
galaxy One of countless swirling, massive
clusters of solar systems in the universe.
gravitational attraction The force of gravity
that causes objects to be attracted to one
another.
gravity The attractive force that exists
between objects.
Jupiter The fifth planet from the Sun in our
Solar System.
light-year A unit of distance, equal to the
distance light travels in a year—about
9.46 trillion km.
map A scale drawing used to represent
geographic locations and their relative
distances from one another.
Mars The fourth planet from the Sun in our
Solar System.
mass The measure of the amount of material
an object contains.
delta science modules Solar System
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Mercury The planet closest to the Sun in our
Solar System.
meteor A meteoroid falling through a planet’s
atmosphere and burning brightly because
of friction.
meteorite The part of a meteor that crashes
into the surface of a satellite.
meteoroid One of countless bits of rock and
metal, smaller than asteroids, that orbit
the Sun or a planet.
meter The international standard unit of length.
Milky Way The galaxy of which our Solar
System is a member.
millimeter A unit of length equal to one
thousandth of a meter.
mnemonic device A memory aid, such as a
made-up sentence or rhyme, that helps
recall the order of items in a list.
moon A satellite of a planet.
mythology The study of myths.
Neptune The eighth planet from the Sun in our
Solar System.
North Star (Polaris) The star almost directly
above the north pole of the Earth.
orbit The elliptical path that a satellite travels
as it moves around a star or a planet.
Orion A constellation near Gemini and Taurus.
perihelion The point along a planet’s orbit at
which it is nearest to the Sun.
planet A large, spherical satellite of a star.
Pluto Once called the ninth planet from the
Sun in our Solar System; now classified as
a dwarf planet.
radius (plural: radii) The distance on a circle
from the focus to the circumference.
ratio A numerical representation of a
relationship between two measurements,
as in a scale for a drawing or a model.
relative brightness The brightness of an
object when compared with the brightness
of surrounding objects.
relative distance The distance between
objects when compared with the distance
between surrounding objects.
relative size The size of an object when
compared with the size of surrounding
objects.
revolution One complete orbit of a satellite.
revolve To travel around another object.
rotation One complete turn of a satellite
about its axis.
satellite An object in orbit around a larger
object.
Saturn The sixth planet from the Sun in our
Solar System.
scale A proportion used in determining the
relationship between two measurements of
size or distance.
scale drawing A two-dimensional scaled
representation of a smaller or larger object.
solar system A star and all the satellites that
orbit it.
star An extremely large, hot ball of glowing
gas that radiates light and heat.
Sun The star of our Solar System.
system An interdependent group of items that
form a unified whole.
universe The vast space that surrounds and
includes all the galaxies as well as all other
existing matter and energy.
Uranus The seventh planet from the Sun in
our Solar System.
Venus The second planet from the Sun in our
Solar System.
year The length of time a planet takes to make
one complete revolution around the Sun.
Note: The Delta Science Reader includes its
own glossary of terms.
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glossary
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