ASTR 1102 FINAL EXAM 2025 ( QUESTIONS WITH
100% CORRECT VERIFIED ANSWERS)
|GUARANTEED PASS| GRADED A+
Parsecs are used to measure:
A) Distance
B) Time
C) Speed - ANSWER A
Star A is seen at a parallax angle of 0.2 arcsec while Star B at an angle of 1.2 arcsec. Which star
is further away and by how much/less?
A) Star A is 6 times further away
B) Star B is 6 times away
C) Star A is 10 times further away
D) They are both at the same distance - ANSWER A
Mars is approximately twice as far from the Sun as Venus. How much dimmer does the Sun
appear from Mars?
A) Half as bright
B) One third as bright
C) One quarter as bright
D) One sixteenth as bright - ANSWER C
Two stars have the same temperature and luminosity, but one is 10 light years from the Earth,
and the other is 1000 light years away. The more distant star appears to be
A) 10x fainter
B) 100x fainter
,C) 10,000x fainter
D) 100,000,000x fainter
E) The same brightness - ANSWER C
α Fic has the same mass as the Sun, but is about 100x more luminous. If the Sun has a total
lifetime around 10 billion years, how long would you expect α Fic to live, to the nearest power
of ten?
Hint: For stars of the same mass, the life-time ranges as one over the star's luminosity (i.e. the
more luminous stars live shorter lives).
A) 100 billion years
B) 1 billion years
C) 10 billion years
D) 100 million years
E) 1000 billion years - ANSWER D
The apparent brightness of a star is 3 x 10^-10 W m-2 and it's parallax 0.05 arcsec. Estimate the
star's lifetime as compared to that of the sun. Round up your final answer.
Hint: Convert parsecs to meters (Google it) before using inverse-square law.
The luminosity of the Sun is 3.846 x 10^26 W.
A) Star will live 4 times longer than the sun
B) Star will have about a quarter of the sun's lifetime
C) Star will live about the same time as the sun
D) Star will have about half of the sun's lifetime - ANSWER B
,Star A has a magnitude of 2 while Star B a magnitude of 6. How much brighter is Star A from
Star B?
A) Star A is (2.5)x(2.5)x(2.5)x(2.5)x(2.5)x(2.5) brighter
B) Star A is 2.5 times brighter
C) Star A is 4 times brighter
D) Star A is (2.5)x(2.5)x(2.5)x(2.5) times brighter - ANSWER D
Parallax allows us to measure a star's distance and a ground-based telescope allows us to
measure it's apparent magnitude. Do we have enough information to calculate the star's
luminosity?
A) Yes
B) No
C) Maybe - not enough information is provided - ANSWER C
You are given a star's distance modulus and the information that there is a lot of dust along the
line of sight. Is the distance you estimate using the distance modulus formula:
A) Underestimated?
B) Overestimated?
C) Unaffected? - ANSWER B
A star has an apparent magnitude of +4.3 but it lays behind clouds of interstellar dust. What
would be the apparent magnitude of the star if there was no dust along the line of sight?
A) +4.3
B) Higher than +4.3
C) Lower than +4.3
D) Meh...another one bites the dust! - ANSWER C
, Star A and Star B have the same temperature.
Star A is a lot more luminous than Star B.
A) Star A is much larger than star B
B) Star A is much smaller than star B
C) Star A is closer than star B
D) Star A is further away than star B - ANSWER A
Star 1 has temperature 10,000 degrees and radius 5 Rsun.
Star 2 has temperature 5,000 degrees and radius 10 Rsun.
What is the ratio of their luminosities (L1/L2)?
A) 1
B) 2
C) 4
D) 16 - ANSWER C
Is our Sun typical?
A) Yes, in the middle of the HR diagram
B) No, it's brighter than most stars - ANSWER A
Which of the following stellar quantities is harder to measure?
A) Temperature
B) Distance
C) Mass
100% CORRECT VERIFIED ANSWERS)
|GUARANTEED PASS| GRADED A+
Parsecs are used to measure:
A) Distance
B) Time
C) Speed - ANSWER A
Star A is seen at a parallax angle of 0.2 arcsec while Star B at an angle of 1.2 arcsec. Which star
is further away and by how much/less?
A) Star A is 6 times further away
B) Star B is 6 times away
C) Star A is 10 times further away
D) They are both at the same distance - ANSWER A
Mars is approximately twice as far from the Sun as Venus. How much dimmer does the Sun
appear from Mars?
A) Half as bright
B) One third as bright
C) One quarter as bright
D) One sixteenth as bright - ANSWER C
Two stars have the same temperature and luminosity, but one is 10 light years from the Earth,
and the other is 1000 light years away. The more distant star appears to be
A) 10x fainter
B) 100x fainter
,C) 10,000x fainter
D) 100,000,000x fainter
E) The same brightness - ANSWER C
α Fic has the same mass as the Sun, but is about 100x more luminous. If the Sun has a total
lifetime around 10 billion years, how long would you expect α Fic to live, to the nearest power
of ten?
Hint: For stars of the same mass, the life-time ranges as one over the star's luminosity (i.e. the
more luminous stars live shorter lives).
A) 100 billion years
B) 1 billion years
C) 10 billion years
D) 100 million years
E) 1000 billion years - ANSWER D
The apparent brightness of a star is 3 x 10^-10 W m-2 and it's parallax 0.05 arcsec. Estimate the
star's lifetime as compared to that of the sun. Round up your final answer.
Hint: Convert parsecs to meters (Google it) before using inverse-square law.
The luminosity of the Sun is 3.846 x 10^26 W.
A) Star will live 4 times longer than the sun
B) Star will have about a quarter of the sun's lifetime
C) Star will live about the same time as the sun
D) Star will have about half of the sun's lifetime - ANSWER B
,Star A has a magnitude of 2 while Star B a magnitude of 6. How much brighter is Star A from
Star B?
A) Star A is (2.5)x(2.5)x(2.5)x(2.5)x(2.5)x(2.5) brighter
B) Star A is 2.5 times brighter
C) Star A is 4 times brighter
D) Star A is (2.5)x(2.5)x(2.5)x(2.5) times brighter - ANSWER D
Parallax allows us to measure a star's distance and a ground-based telescope allows us to
measure it's apparent magnitude. Do we have enough information to calculate the star's
luminosity?
A) Yes
B) No
C) Maybe - not enough information is provided - ANSWER C
You are given a star's distance modulus and the information that there is a lot of dust along the
line of sight. Is the distance you estimate using the distance modulus formula:
A) Underestimated?
B) Overestimated?
C) Unaffected? - ANSWER B
A star has an apparent magnitude of +4.3 but it lays behind clouds of interstellar dust. What
would be the apparent magnitude of the star if there was no dust along the line of sight?
A) +4.3
B) Higher than +4.3
C) Lower than +4.3
D) Meh...another one bites the dust! - ANSWER C
, Star A and Star B have the same temperature.
Star A is a lot more luminous than Star B.
A) Star A is much larger than star B
B) Star A is much smaller than star B
C) Star A is closer than star B
D) Star A is further away than star B - ANSWER A
Star 1 has temperature 10,000 degrees and radius 5 Rsun.
Star 2 has temperature 5,000 degrees and radius 10 Rsun.
What is the ratio of their luminosities (L1/L2)?
A) 1
B) 2
C) 4
D) 16 - ANSWER C
Is our Sun typical?
A) Yes, in the middle of the HR diagram
B) No, it's brighter than most stars - ANSWER A
Which of the following stellar quantities is harder to measure?
A) Temperature
B) Distance
C) Mass
