Astronomy 101 -- Worksheet #5
THE SOLAR SYSTEM and PLANET EARTH
1) The solar system is made up of one star, the _____________, 9 _____________, and many
______________, _________________, _______________, and ______________.
2) One major difference between a star and a planet is that stars ____________ light, while planets
_____________ light.
3) The 9 planets, in order of increasing average distance from the Sun, are _____________,
_____________, _____________, _____________, _____________, _____________, _____________,
_____________, and _____________.
4) The outer 3 planets are not visible to the naked eye, and were not discovered until after the invention
of the telescope. These planets are _____________, _____________, and _____________.
5) The planets all orbit the Sun in the plane known as the _____________. This orbital motion is also
called _____________. The plane of Pluto’s orbit exhibits the largest _____________ of all the planetary
orbits relative to the ecliptic, with an inclination of about 17°.
6) The Sun contains over __________% of the mass of the solar system. Most of the remaining
__________% is found in _____________.
7) The overall shape of the solar system is ____________________. This is known because the planets
are always seen to be close to the _____________ in the sky.
8) The planets all _____________ around the the Sun, and most planets _____________ on their axes, in
the same direction -- counterclockwise as seen from the North.
9) The orbits of the planets, comets, and asteroids around the Sun are ellipses with the Sun at one focus
(according to _____________ _____________ Law). However, the planetary orbits are ellipses which
are nearly _____________, while cometary orbits are ellipses which are highly _____________.
10) The radius of the Sun is about _____________ times larger than that of the Earth, while the radius of
the Earth is about _____________ times larger than that of the Moon. Since the volume of a sphere depends on the cube of the radius, the volume of the Sun is about _____________ times larger than that of
the Earth, while the volume of the Earth is about _____________ times larger than that of the Moon.
11) The distance from the Earth to the Sun is about 150,000,000 km or 93,000,000 miles. This distance
is known as the ____________________.
12) The distances of the planets from the Sun can all be measured relative to the ____________________
using trigonometry. The Astronomical Unit can then be measured relative to the
____________________.
13) One way of classifying the planets is in terms of their distance from the Sun. The planets which are
closer to the Sun than Earth are known as _____________, while those which are farther from the Sun
than Earth are known as _____________. The _____________ planets can never be seen at midnight,
while the _____________ planets can be seen during the middle of the day or night.
14) When planets are classified in terms of their physical properties, the major categories are the Earthlike, or _______________ planets, and the Jupiter-like, or _______________ planets. The
-2_______________ planets are smaller with high densities (like rock), while the _______________ planets
are larger with low densities (like water).
15) The force which binds the planets to the Sun in the solar system is known as _______________. The
strength of the force of _____________ between the Sun and planet X depends on the _____________ of
the Sun, the _____________ of planet X, and the _____________ of the distance between them. If the
mass of the planet or the Sun increases, the force will _____________ in proportion, and if the distance
between the planet and the Sun increases the force will _____________ as the square of the distance between them.
16) Suppose you discover a new planet which is found to be 6 A.U. from the Sun with the same mass as
that of the Earth. Relative to the force of _____________ between the Sun and the Earth, the force between the Sun and the new planet will be _____________ times _____________ (stronger/weaker).
17) Astronomers use measurements of the orbits of moons, planets, stars, and galaxies to determine the
_____________ of objects in the Universe. This procedure is based on Kepler’s _____________ Law.
18) The density of an object is defined as the _____________ divided by the _____________. A familiar
density standard is water -- since 1 gram (1 g) of water is contained in a volume of 1 cubic centimeter (1
cm3), water has a density of 1 g/cm3. Rock has a higher density, between 3 and 5 g/cm3, and oil has a
lower density than water (so it floats on water).
19) Planet Earth is the largest of the _____________ planets. The atmosphere which surrounds our planet serves both to _______________________ and ______________________ as well as provide oxygen
for us to breathe.
20) The Earth’s atmosphere is composed of 77% _____________, 21% _____________, and traces of
other gases (including argon, water vapor, carbon dioxide and ozone).
21) The trapping of heat near the surface of a planet by molecules (such as CO2) in the atmosphere is
known as the _______________ effect. This effect is very significant on the planet _____________, and
is becoming more so on the Earth as we burn more fossil fuels to produce energy.
22) The Earth’s interior is probed by seismic waves which pass through our planet after they are produced in _____________. The general features of the Earth’s interior include the _____________, the
_____________, and the _____________. The outer _____________ is liquid, while the inner
_____________ is solid.
23) The Earth behaves like a magnet, with a magnetic field which is generated in the
____________________. It is because of the Earth’s magnetic field that a compass points North (to magnetic North, that is).
24) The surface of the Earth changes slowly over time, due to the process known as
____________________. The surface of the Earth appears to be made of ∼10 large _____________
which float on the mantle. As these _____________ collide, separate, or pass by each other, we experience
____________________,
____________________,
___________________,
and
____________________.