Unit 4 Unit Review Answers
1. a) universe
e) nuclear fusion
2. a) False (There is evidence of stars with planets in orbit around them)
c) False (A light-year is a unit of distance)
e) False (The longest baseline possible is the diameter of Earth’s orbit
around the Sun)
g) False (Auroras are caused by high-energy particles from the Sun
striking Earth’s atmosphere)
h) False (~95% of the stars are smaller than the Sun)
j) False (Stars that become red super-giants have a mass that is at
least 10 times that of the Sun)
m) False (Probes have been sent only to bodies in the solar system)
3. a) A star constellation is a group of stars visible from Earth. In space,
the stars of a constellation may be very far apart; they just look
close from our point of view. A star cluster is a group of stars too few
in number to be called a galaxy.
b) Earth’s rotation is the spinning on its axis, which takes one day.
Earth’s revolution is its motion in a path around the Sun, which takes
c) An asteroid is a small rocky object in orbit around the Sun in the
asteroid belt, which is between Mars and Jupiter. A comet, which is
a chunk of frozen matter, also orbits the Sun, but the orbit is very
d) A galaxy is a huge collection of stars and gases that travel together
in the Universe. A star cluster is a group of stars much smaller than a
e) Interplanetary distances are distances between planets, which are
relatively small distances. Intergalactic distances are distances
f) A solar flare is a burst of high-speed particles from the Sun’s
chromosphere; it lasts for only a few minutes. A solar prominence is
a huge sheet of glowing gases forced out from the Sun’s
chromosphere; it can last days or weeks.
g) Apparent magnitude is the brightness of a star as observed from
Earth. Absolute magnitude is the true brightness of a star as it would
be observed from the same distance from all other stars.
h) A neutron star is a very dense star core; it is created when a high
mass star reaches its final stages. A black hole is an extremely
dense star core; it is created when a star of very high-mass reaches
its final stages and collapses; its gravitational field is so strong that
nothing escapes from it.
i) Both vehicles need oxygen and fuel to operate. An aircraft can
operate in the atmosphere. A spacecraft can travel above the
atmosphere because it carries its own oxygen supply.
j) A vacuum has no particles. The atmosphere contains gas and
water vapour particles. It extends to about 150 km above Earth’s
k) Satellites are objects that travel in orbits around other objects. A
natural satellite occurs in nature, such as the Moon orbiting Earth.
An artificial satellite is human-made, such as a communications
l) A space shuttle is a vehicle that takes astronauts and cargo into low
Earth orbit for relatively short periods of time (often between 7 and
10 days). It is used to deploy and retrieve satellites and carry
astronauts to and from the space station. A space station is a long-
lasting vehicle in which astronauts can live and work for several
months at a time. It is used mainly for scientific experimentation.
Both vehicles travel above Earth’s atmosphere.
13. The gas giants have the biggest number of moons. This likely
occurred because the gas giants have a large mass, so their force
of gravity is strong enough to have attracted other bodies.
16. Two stars of equal luminosity can have different apparent
magnitudes if they are different distances from Earth.
17. The temperature of a star can be judged by the colour of the star.
Thus, red stars are the coolest, followed by orange, yellow, white
and the hottest is a blue star.
18. Only the most massive stars, those whose mass is 10 or more times
that of the Sun, tend to become supernovas. After that stage, the
core collapses into a neutron star or black hole, and the outer layers
26. The bluish star has a higher temperature than the yellowish star.
27. As the height of the orbit increases, the speed of the satellite