Assignments 3-7

Question 1

what was the greatest inaccuracy in Copernicus’ model of the solar system?

a) that the planets travelled in circular orbits with uniform motion
b) that the planets travelled on epicycles, the centers of which followed orbits around the sun
c) that the planets travelled in elliptical orbits
d) that the planets were allowed to travel backwards in their orbits

Answer 1

a) that the planets travelled in circular orbits with uniform motion

Question 2

What two numbers tell us the size and shape of an ellipse?

a) radius, eccentricity
b) radius, deferent
c) semi-major axis, deferent
d) semi-major axis, eccentricity

Answer 2

d) semi-major axis, eccentricity

Question 3

Given its orbital period of 76 years, what is the average distance of Comet Halley from the Sun?

a) 18 AU
b) 38 AU
c) 54 AU

Answer 3

a) 18 AU

Question 4

An object has been located orbiting the sun at a distance of 65 AU. What is the approximate orbital period of this object?

a) 8.1 years
b) 65 years
c) 524 years
d) 4225 years

Answer 4

c) 524 years

Question 5

On average, Saturn is 10 AU from the Sun. What is the approximate orbital period of Saturn?

a) 10 years
b) 32 years
c) 1000 years
d) 3200 years

Answer 5

b) 32 years

Question 6

At which lunar phase(s) are tides at their lowest?

a) both new moon and first quarter moon
b) both first quarter moon and third quarter moon
c) new moon
d) full moon

Answer 6

b) both first quarter moon and third quarter moon

Question 7

If mars rises approximately the same time as a particular star. If mars is in normal prograde motion at what time Mars will rise next night?

a) same time as the star
b) earlier than the star
c) later than the star

Answer 7

c) later than the star

Question 8

The surface temperature of the sun is about 5800K. Based on this temperature, what is the expected peak wavelength of radiation?

a) orange
b) green
c) yellow
d) red

Answer 8

b) green

Question 9

What is found in the centers of granules?

a) hot material rising to the photosphere from below
b) cool material falling from the photosphere to the regions below
c) material that is fainter and hotter than its surroundings
d) material that is brighter and cooler than its surroundings

Answer 9

a) hot material rising to the photosphere from below

Question 10

Which of the following can be determined from the spectrum of a star, without additional information?

a) radial velocity
b) core temperature
c) distance

Answer 10

a) radial velocity

Question 11

Which of the following can we use to determine the surface temperature of a star?

a) determining if the star has a companion star
b) studying its line absorption spectrum
c) measuring the stars distance
d) measuring the stars parallax

Answer 11

b) studying its line absorption spectrum

Question 12

Lowest surface Temperature?

For F8
Cet M7
Tri A0
Per O7

Answer 12

Cet M7

Question 13

Highest surface temperature?

For F8
Cet M7
Tri A0
Per O7

Answer 13

Per O7

Question 14

How do we know that giant stars are larger in diameter than the sun?

a) they are more luminous but have about the same temperature
b) they are less luminous but have about the same temperature
c) they are hotter but have the same luminosity
d) they are cooler but have the same luminosity

Answer 14

a) they are more luminous but have about the same temperature

Question 15

Sirius A and B are two stars at the same distance from the earth. In this binary system, Sirius A is much brighter but Sirius B is much hotter. From this information, what can you conclude about the two stars?

a) Sirius B must be much smaller than Sirius A
b) Sirius B must be much larger than Sirius A
c) Sirius B must be more massive than Sirius A
d) Sirius B must be much less massive than Sirius A

Answer 15

a) Sirius B must be much smaller than Sirius A

Question 16

The star named Circini is of Spectral type and luminosity class of O 8.5 V. Based on this, how does Cirini compare to the Sun?

a) Circini is cooler and larger than the Sun
b) Circini is cooler and smaller than the Sun
c) Circini is hotter and more luminous than the sun
d) Circini is hotter and larger than the Sun

Answer 16

c) Circini is hotter and more luminous than the sun

Question 17

Approximately, what basic composition are all stars born with?

d) three quarters hydrogen, one quarter helium, no more than 2 percent heavier elements

Answer 17

d) three quarters hydrogen, one quarter helium, no more than 2 percent heavier elements

Question 18

Suppose that you measure the parallax angle for a particular star to be 0.5 arcseconds. The distance to this star is

a) 0.5 light year
b) 5 light years
c) 0.5 parsec
d) 2 parsec

Answer 18

d) 2 parsec

Question 19

Which of the following characteristics of stars has the greatest range in values?

a) luminosity
b) radius
c) surface temperature
d) mass

Answer 19

a) luminosity

Question 20

A star of spectral type O lives approximately how long on the main sequence?

a) 1,000 years
b) 100 million years
c) 10 million years
d) 10,000 years

Answer 20

c) 10 million years

Question 21

What physical property of a star does the spectral type measure?

a) luminosity
b) density
c) mass
d) temperature

Answer 21

d) temperature

Question 22

Two red stars have surface temperature of 3000K, but Star’s A luminosity is about 5% of the Sun’s and Star’s B’s luminosity is about 32,000 times the luminosity of the sun. How much bigger is star B than star A?

a) They are the same size.
b) Star B’s radius is about 640,000 times larger than Star A’s radius
c) Star B’s radius is about 800 times larger than Star A’s radius
d) Star B’s radius is about 16 times larger than Star A’s radius

Answer 22

c) Star B’s radius is about 800 times larger than Star A’s radius

Question 23

Star A is a main sequence star of spectral type F2 and star B is a white dwarf of spectral type B4. Which statement below is correct?

a) star A appears brighter than star B
b) star B appears brighter than star A
c) Star A is hotter than star B
d) Star B is hotter than star A

Answer 23

d) Star B is hotter than star A

Question 24

Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral type K2. Which statement below is correct?

a) star A appears brighter than star B
b) star B appears brighter than star A
c) Star A is hotter than star B
d) Star B is hotter than star A

Answer 24

c) Star A is hotter than star B

Question 25

Compared to the size of the Sun, in what range of sizes are nearly all stars found? a) 0.01 to 100 solar radii b) 0.5 to 50 solar radii c) 0.5 to 2 solar radii d) 0.1 to 1.0 solar radii

Answer 25

a) 0.01 to 100 solar radii

Question 26

The Hertzsprung-Russell Diagram plots ______ against the spectral type or temperature. a) brightness or apparent magnitude b) luminosity or absolute magnitude c) size or density d) distance

Answer 26

b) luminosity or absolute magnitude

Question 27

How might the most common occurring stars be described, based on our stellar neighbourhood? a) K giants b) M main sequence c) G main sequence d) white dwarfs

Answer 27

b) M main sequence

Question 28

In general, the narrower the spectral line of a star: a) the bigger the star is b) the hotter the star is c) the denser the star is d) the smaller the star is

Answer 28

a) the bigger the star is

Question 29

Upon what data do measurements of sizes of eclipsing binaries depend? a) their orbital periods b) their masses and luminosities c) their temperatures and speeds d) their Doppler shifts and durations of stages of their eclipses

Answer 29

d) their Doppler shifts and durations of stages of their eclipses

Question 30

Which type of binary can have their sizes measured directly by photometry? a) visual b) eclipsing c) virtual d) spectroscopic

Answer 30

b) eclipsing

Question 31

In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be: a) 240 years b) 90 years c) 60 years d) 120 years

Answer 31

a) 240 years

Question 32

In spectroscopic binary system, the star showing the larger blueshift is: a) cooler and receding the fastest b) less massive of the pair and receding slower c) more massive and approaching us d) less massive and approaching us at this moment

Answer 32

d) less massive and approaching us at this moment

Question 33

In a spectroscopic binary, if a pair shows a combined set of lines tonight, but a maximum split two nights later, its orbital period must be: a) four days b) eight days c) one day d) two days

Answer 33

b) eight days

Question 34

In eclipsing binaries, in contrast to spectroscopic binaries, we can also determine a star's: a) temperature b) speed c) color d) radius

Answer 34

d) radius

Question 35

Eclipsing binaries are less common than spectroscopic binaries because: a) their orbital planes must be nearly edge on from our perspective b) both stars must have the same diameter c) their orbital planes must be nearly face on from our perspective d) both stars must have the same mass

Answer 35

a) their orbital planes must be nearly edge on from our perspective

Question 36

What is the single most important characteristic in determining the course of a star's evolution? a) density b) absolute magnitude c) mass d) distance

Answer 36

c) mass

Question 37

What is the typical main sequence lifetime of a G-type star? a) 100 million years b) 10 billion years c) 1 billion years d) 10 million years

Answer 37

b) 10 billion years

Question 38

A star's motion towards or away from us is detected by the ____ of spectral lines. a) proper motion of the spectral lines b) Lines spectroscopy c) Doppler Shift d) Ecliptic spectroscopy

Answer 38

c) Doppler Shift

Question 39

The _____ magnitude of a star depends directly upon its luminosity and distance a) Absolute b) Visual c) Bolometric d) Apparent

Answer 39

d) Apparent

Question 40

If two stars are the same size and one is twice the temperature of the other, how much more luminous is the hotter one? a) 8 times b) 16 times c) 100 d) 25

Answer 40

b) 16 times

Question 41

For a star of 10 solar masses, its main sequence life span will be: a) about the same as the Sun's b) ten times longer than our Sun's c) only a tenth of the Sun's d) only 1/1000th of the Sun

Answer 41

d) only 1/1000th of the Sun

Question 42

All classes of binary stars yield the basic information on stellar ____. a) spectral type b) period c) Masses d) Radii

Answer 42

c) Masses

Question 43

In an eclipsing binary, the longer the stages of the eclipse take, the ____ the star. a) larger b) the faster c) Hotter d) Massive

Answer 43

a) larger

Question 44

What role does helium play in spectral classification? a) Radiates on the 1420 MHz line b) It absorbs the energy of the spectral lines c) it is ionized in the hottest O class stars d) It converts into nitrogen

Answer 44

c) it is ionized in the hottest O class stars

Question 45

Astronomers estimate that new starts from in our galaxy at the rate of about a) 20-50 per year b) 1 per year c) a few (2-3) per year d) 10 per year

Answer 45

c) a few (2-3) per year