Download Study Guide #3 Answer Key

Final Exam Study Guide 3
1. What characteristics do scientists use to classify stars?
ANS: Stars are classified by their color, temperatures, sizes, and brightness.
2. What two parts and characteristics of a wave determine the amount of energy carried in?
The wave?
ANS: Amplitude: The larger the amplitude the more energy is carried by the wave.
Wavelength: The shorter the wavelength the more energy is carried by the wave.
Frequency: The higher the frequency the more energy is carried by the wave.
3. What major feature of the outer planets makes them so different than the inner ones?
ANS: The inner planets and outer planets are divided by the asteroid belt. Also inner are all solid and the outer
planets are mostly gaseous.
INNER PLANETS
Small
Earth is the largest of the Inner Planets,
with a diameter of 12,756 km (7,926
miles). Mercury is the smallest with a
diameter of 4,878 km (3,031 miles)
Have solid surfaces and thin/no
atmospheres
In theory, it would be possible to stand
on each of the Inner Planets, although
you would only survive on Earth.
OUTER PLANETS
Huge!
Jupiter, the largest planet, has a
diameter of 142,984 km (88,846 miles).
Neptune is the smallest of the Outer
Planets with a diameter of 49,532 km
(30,779 miles)
Balls of gas with no surface
Most of the Outer Planets are made of
gas. It is likely that they have a much
smaller solid or liquid centre. It would be
impossible to stand on any of the Outer
Planets.
Greater Density
Smaller Density
The size and composition of the planets
is caused by the density of the elements Despite being larger, the elements that
that make up the planets. The elements
make up the Outer Planets are less
in the Inner Planets are more closely
densely packed together causing them to
packed together, causing them to be
be quite light for their size.
smaller on solid.
Varied atmospheres
The contents of the atmospheres of the
Inner Planets varies from planet to
planet. Mercury has no atmosphere
although Sodium and Helium can be
detected above the surface. Venus'
atmosphere is mostly Carbon Dioxide
with a very small amount of Nitrogen.
Earth's atmosphere is mostly Nitrogen
with a smaller amount of Oxygen and
even smaller amounts of other gases.
Mars has a similar composition of carbon
dioxide and nitrogen as Venus although
has a much thinner atmosphere.
The atmospheres of the Outer Planets
consist mostly of Hydrogen and Helium,
with Methane also being present in the
atmospheres of Uranus and Neptune.
Other gases are present although in
much smaller quantities.
Known by the ancients
Not known by the ancients
Similar atmospheres
The existence of the Inner Planets has
been known about for thousands of
years. The earliest astronomers didn't
know that the four objects (including
Earth) were planets, but they knew they
existed.
Spin slowly
Of the Outer Planets, only Jupiter and
Saturn were observed by ancient
astronomers. The existence of Uranus
and Neptune was not known until
relatively recently. Uranus was
discovered in 1781 and Neptune in
1846.
Spin quickly
All of the Outer Planets spin quicker than
Compared to the much larger Outer
the Inner Planets. Uranus spins slowest,
Planets, the Inner Planets spin quite
taking 17 hours and 14 minutes to spin
slowly. Earth spins the quickest, taking
on its axis. Jupiter takes only 9 hours
23 hours and 56 minutes to spin on its
and 55 minutes to spin on its axis. This
axis. Venus takes 243 days to spin on its rapid rotation causes Jupiter and Saturn
axis, spinning in an opposite direction to
to appear squashed, wider across the
the other planets.
equator than from top to bottom.
Orbit the Sun slowly
The Outer Planets orbit the Sun from
Orbit the Sun quickly
millions of miles and have a much
Because they are quite close to the Sun,
greater distance to cover to complete an
the Inner Planets complete an orbit
orbit, so take much longer to do so.
quickly. Mercury takes only 88 days to
Jupiter takes almost 12 years to
orbit the Sun. Mars takes 687 days.
complete an orbit and Neptune take over
164 years.
Few Moons
Lots of Moons
All of the Outer Planets have many
Only Earth and Mars have moons orbiting
moons orbiting them. There are 63
them. One moon orbits Earth and two
moons known to orbit Jupiter, 60
small moons orbit Mars.
orbiting Saturn, 27 orbiting Uranus and
13 orbiting Neptune.
Rings
None of the Inner Planets have rings
orbiting them
All of the Outer Planets have rings
orbiting them. The rings are thin discs of
dust and rocks possibly caused by
moons being broken up or not being
completely formed while orbiting the
planet. Saturn has the most visible ring
system of any of the planets.
Multiple space craft visitors
All Outer Planets visited by one
space craft
No rings
Due to being close to Earth, there have
been several missions to the other Inner
Planets, especially to Mars and Venus.
Mercury has been visited by two
spacecrafts.
There have been multiple visits to
Jupiter and Saturn, but Uranus and
Neptune have only been visited once.
This was by Voyager 2 (which also
visited Jupiter and Saturn).
4. What inner planet has the least mass?
ANS: Jupiter is by far the most massive planet; Saturn trails it. Uranus, Neptune, Earth, Venus,
Mars, and Pluto are orders of magnitude less massive. Therefore, Mars is planet with the least
mass. It would have been
Pluto but it is no longer considered a planet. However, on your EOC, if asked the answer would be
Pluto.
Similarities between Venus and Earth
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Diameter (and therefore total volume also) (Venus has diameter 95% of Earth's)
Average Density
Total Mass (Venus is 81% of Earth's mass)
Differences between Venus and Earth

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

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Surface temperature on Venus is about 750K
Venus's atmosphere is mainly Carbon Dioxide, which is a very small constituent of Earth's atmosphere
Venus has no surface water
The atmospheric pressure on Venus is about 90 times that of the Earth.
Venus is permanently covered by thick cloud
Rotation of Venus = 243 Earth days
Sense of Rotation - Venus rotates in a retrograde motion in comparison with most other bodies of the Solar
System, and definitely opposite that of the Earth <LI
No Moon
The differences between the inner planets are the size, atmosphere, composition, and crust activity.
5. Describe the Milky Way galaxy.
The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a
barred spiral galaxy that is part of the Local Group of galaxies. It is one of billions of galaxies in the observable
universe.
The Milky Way galaxy, as viewed from Earth, itself situated on a spur off one of the spiral arms of the galaxy
(see Sun's location and neighborhood), appears as a hazy band of white light in the night sky arching across the
entire celestial sphere and originating from stars and other material that lie within the galactic plane. The plane
of the Milky Way is inclined by about 60° to the ecliptic (the plane of the Earth's orbit), with the North Galactic
Pole situated at right ascension 12h 49m, declination +27.4° (B1950) near beta Comae Berenices. The South
Galactic Pole is near alpha Sculptoris.
The center of the galaxy is in the direction of Sagittarius, and the Milky Way then "passes" (going westward)
through Scorpius, Ara, Norma, Triangulum Australe, Circinus, Centaurus, Musca, Crux, Carina, Vela, Puppis,
Canis Major, Monoceros, Orion & Gemini, Taurus, Auriga, Perseus, Andromeda, Cassiopeia, Cepheus &
Lacerta, Cygnus, Vulpecula, Sagitta, Aquila, Ophiuchus, Scutum, and back to Sagittarius.
The Milky Way looks brightest in the direction of the constellation of Sagittarius, toward the galactic center.
Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the
constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic
relative to the galactic plane. The fact that the Milky Way divides the night sky into two roughly equal
hemispheres indicates that our Solar System lies close to the galactic plane. The Milky Way has a relatively low
surface brightness, making it difficult to see from any urban or suburban location suffering from light pollution.
The stellar disk of the Milky Way galaxy is approximately 100,000 light-years (9.5×1017 km) in diameter, and is
believed to be, on average, about 1,000 ly (9.5×1015 km) thick.[7] It is estimated to contain at least 200 billion
stars[8] and possibly up to 400 billion stars,[9] the exact figure depending on the number of very low-mass stars,
which is highly uncertain. Extending beyond the stellar disk is a much thicker disk of gas. Recent observations
indicate that the gaseous disk of the Milky Way has a thickness of around 12,000 ly (1.1×1017 km)—twice the
previously accepted value.[10] As a guide to the relative physical scale of the Milky Way, if it were reduced to
100 m in diameter, the Solar System, including the Oort Cloud, would be no more than 1 mm in width.
The Galactic Halo extends outward, but is limited in size by the orbits of two Milky Way satellites, the Large
and the Small Magellanic Clouds, whose perigalacticon is at ~180,000 ly (1.7×1018 km).[11] At this distance or
beyond, the orbits of most halo objects would be disrupted by the Magellanic Clouds, and the objects would
likely be ejected from the vicinity of the Milky Way.
Recent measurements by the Very Long Baseline Array (VLBA) have revealed that the Milky Way is much
larger than previously thought. The size of our home galaxy is now considered to be roughly similar to that of
our largest local neighbour, the Andromeda galaxy. By using the VLBA to measure the apparent shift of farflung star-forming regions when the Earth is on opposite sides of the Sun, the researchers were able to measure
the distance to those regions using fewer assumptions than prior efforts. The newer and more accurate estimate
of the galaxy's rotational speed (and in turn the amount of dark matter contained by the galaxy) puts the figure
at about 254 km/s, significantly higher than the widely accepted value of 220 km/s.[12] This in turn implies that
the Milky Way has a total mass equivalent to around 3 trillion suns, about 50% more massive than previously
thought.[13]
Age
It is extremely difficult to define the age at which the Milky Way formed, but the age of the oldest star in the
Galaxy yet discovered, HE 1523-0901, is estimated to be about 13.2 billion years, nearly as old as the Universe
itself.[1]
This estimate is based on research by a team of astronomers in 2004 using the UV-Visual Echelle Spectrograph
of the Very Large Telescope to measure, for the first time, the beryllium content of two stars in globular cluster
NGC 6397.[14][citation needed] From this research, the elapsed time between the rise of the first generation of stars in
the entire Galaxy and the first generation of stars in the cluster was deduced to be 200 million to 300 million
years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they
estimated the age of the oldest stars in the Milky Way at 13.6 ± 0.8 billion years. Based upon this emerging
science, the Galactic thin disk is estimated to have been formed between 6.5 and 10.1 billion years ago.
Composition and structure
The Galaxy consists of a bar-shaped core region surrounded by a disk of gas, dust and stars forming four
distinct arm structures spiralling outward in a logarithmic spiral shape (see Spiral arms). The mass distribution
within the Galaxy closely resembles the Sbc Hubble classification, which is a spiral galaxy with relatively
loosely-wound arms.[16] Astronomers first began to suspect that the Milky Way is a barred spiral galaxy in the
1990s[17] rather than an ordinary spiral galaxy. Their suspicions were confirmed by the Spitzer Space Telescope
observations in 2005[18] which showed the Galaxy's central bar to be larger than previously suspected. The
Milky Way's mass is thought to be about 5.8 × 1011 solar masses (M☉)[19][20][21] comprising 200 to 400 billion
stars. Its integrated absolute visual magnitude has been estimated to be −20.9. Most of the mass of the Galaxy is
thought to be dark matter, forming a dark matter halo of an estimated 600–3000 billion M☉ which is spread out
relatively uniformly.[21]
Galactic center
The galactic disc, which bulges outward at the galactic center, has a diameter of between 70,000 and 100,000
light-years.[22] The distance from the Sun to the galactic center is now estimated at 26,000 ± 1400 light-years,
while older estimates could put the Sun as far as 35,000 light-years from the central bulge.
The galactic center harbors a compact object of very large mass as determined by the motion of material around
the center.[23] The intense radio source named Sagittarius A*, thought to mark the center of the Milky Way, is
newly confirmed to be a supermassive black hole. For a photo see Chandra X-ray Observatory; Jan. 6, 2003
Most galaxies are believed to have a supermassive black hole at their center.[24]
The Galaxy's bar is thought to be about 27,000 light-years long, running through its center at a 44 ± 10 degree
angle to the line between the Sun and the center of the Galaxy. It is composed primarily of red stars, believed to
be ancient (see red dwarf, red giant). The bar is surrounded by a ring called the "5-kpc ring" that contains a
large fraction of the molecular hydrogen present in the Galaxy, as well as most of the Milky Way's star
formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of our own galaxy.[25]
Spiral arms
Each spiral arm describes a logarithmic spiral (as do the arms of all spiral galaxies) with a pitch of
approximately 12 degrees. There are believed to be four major spiral arms which all start near the Galaxy's
center. These are named as follows, according to the image at right:
The galactic disk is surrounded by a spheroid halo of old stars and globular clusters, of which 90% lie within
100,000 light-years,[28] suggesting a stellar halo diameter of 200,000 light-years. However, a few globular
clusters have been found farther, such as PAL 4 and AM1 at more than 200,000 light-years away from the
galactic center. While the disk contains gas and dust which obscure the view in some wavelengths, the spheroid
component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent
areas of high density), but not in the halo. Open clusters also occur primarily in the disk.
Recent discoveries have added dimension to the knowledge of the Milky Way's structure. With the discovery
that the disc of the Andromeda Galaxy (M31) extends much further than previously thought,[29] the possibility
of the disk of our own Galaxy extending further is apparent, and this is supported by evidence of the newly
discovered Outer Arm extension of the Cygnus Arm.[30] With the discovery of the Sagittarius Dwarf Elliptical
Galaxy came the discovery of a ribbon of galactic debris as the polar orbit of Sagittarius and its interaction with
the Milky Way tears it apart. Similarly, with the discovery of the Canis Major Dwarf Galaxy, it was found that a
ring of galactic debris from its interaction with the Milky Way encircles the galactic disk.
The Halo
The Halo consists of the oldest stars known, including about 146 Globular Clusters, believed to have been
formed during the early formation of the Galaxy with ages of 10-15 billion years from their H-R Diagrams. The
halo is also filled with a very diffuse, hot, highly-ionized gas. The very hot gas in the halo produces a gammaray halo.
Neither the full extent nor the mass of the halo is well known. Investigations of the gaseous halos of other spiral
galaxies show that the gas in the halo extends much further than previously thought, out to hundreds of
thousands of light years. Studies of the rotation of the Milky Way show that the halo dominates the mass of the
galaxy, but the material is not visible, now called dark matter.
The Disk
The disk of the Galaxy is a flattened, rotating system which contains the Sun and other intermediate-to-young
stars. The sun sits about 2/3 of the way from the center to the edge of the disk (about 25,000l.y. by the most
modern estimates). The sun revolves around the center of the galaxy about once every 250 million years. The
disk also the galaxy about contains atomic (HI) and molecular (H2) gas and dust.
6. Which of the following events takes the longest time to occur?
a. Earth orbits the Sun once : (365 and a quarter days (365.25). The extra quarter is the reason that we
end up with a leap year once every 4 years, where there are 366 days in the year.)
b. The Moon orbits the Earth twice: (On average it takes 27.322 days for the Moon to complete one
orbit around Earth.) X 2
c. Earth rotates on its axis 5 times: (The Earth is rotating around an axis (called its rotational axis).The
Earth's axis is tipped over about 23.5° from vertical.Earth's rotational axis points in the same direction
relative to the stars, so that the North Pole points towards the star Polaris. Think of the Earth as a
spinning top, tipped over to one side. Over very long time periods (thousands of years) the direction of
Earth's axis slowly changes due to precession.
More specifically, our rotation period (the time elapsed for one rotation) with respect to the stars is
called a sidereal day. A sidereal day is 24 sidereal hours, or 23 hours and 56 minutes on a normal clock.
Our clock time is based on the earth's rotation with respect to the sun from solar noon to solar noon. This
is a solar day, and it is divided into 24 hours. Because Earth travels about 1 / 365 of the way around the
sun during one day, there is a small difference between solar time and sidereal time.)
ANS: Earth Orbits the Sun Once
7. Describe the spacing of particles in solids, liquids and gases.
Gas
liquid
Solid
gas
liquid
solid
assumes the shape and volume
of its container
particles can move past one
another
assumes the shape of the part
of the container which it
occupies
particles can move/slide past
one another
retains a fixed volume and
shape
rigid - particles locked into
place
compressible
lots of free space between
particles
not easily compressible
little free space between
particles
not easily compressible
little free space between
particles
flows easily
particles can move past one
another
flows easily
particles can move/slide past
one another
does not flow easily
rigid - particles cannot
move/slide past one another
8. What causes day and night on Earth?
ANS: Day and night is the result of the rotation of the Earth on its own axis. The axis of the Earth is an imaginary line that
passes through the North and the South poles. The Earth takes approximately twenty-four hours to complete one rotation.
The Sun is the source of light.
At the time of the rotation, it is day on the side of Earth that faces the Sun; while it is night on the other side of Earth not
facing the Sun. The position of the Sun is fixed and it does not change.
The Sun rises in the east because the Earth is moving towards the east. Later, in the mid noon the Sun is in the south
because Earth is moving towards the south and gradually towards the west and the Sun sets.
The length of the day is measured from the time the Sun rises to the time the Sun sets. Another interesting fact about Earth
is that because Earth tilts on its axis, it is day in the southern hemisphere and night in the northern hemisphere and vice
versa.
The axis of the Earth is always tilted at an angle of 23.5 degrees. The rotation of the Earth on its own axis not only results
in day and night but also creates the four seasons (summer, winter, autumn and spring). The summers and winters are
the result of the tilt of the axis of the Earth.
The length of the day and night varies in each season. For instance, the daylight is longer in summer and the night is
shorter. In winter, the nights are longer and the days are short. It is the length of the day and night that determine the
temperature of the seasons and not the revolution of the Earth.