Ast Final Flashcards
I) Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ
mass they are formed with
A starS luminosity is the
total amount of energy that the star radiates each second.
3) If the distance between us and a star is doubled, with everything else remaining the same, its luminosity
remains the same, but its apparent brightness is decreased by a factor of four.
You mesure the parallax angle for a star to be O.I arcseconds. The distance to this star is
10 parsecs.
You mesure the parallax angle for a star to be 0.5 arcseconds. The distance to this star is
2 parsecs.
The spectral sequence sorts stars according to
surtace temperar.
The stellar spectral sequence, in order of decreasing temperature, iS
OBAFGKM.
8) Which of the following statements about spectral types of stars is true?
All of the above are true.
Which of the following terms is given to a pair of stars that appear to change position in the sky, indicating
that they are orbiting one another?
visual binary
Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
surtace temperature on the horizontal axis and luminosity on the vertical axis
11) On a Hertzsprung-Russell diagram, where would you find stars that are cool and dim?
lower right
On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous?
upper right
13) On a Hertzsprung-Russell diagram, where would you find stars that have the largest radii?
Upper right
14) On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass
C) upper left
On a Hertzsprung-Russell diagram, where would you find red giant stars?
A) upper right
On a Hertzsprung-Russell diagram, where would you find white dwarts?
lower left
On the main sequence, stars obtain their energy
by converting hydrogen to helium.
Which of the following luminosity classes refers to stars on the main sequence?
V
Which of the following comparisons between low-mass stars and high-mass main-sequence stars 1s true?
Low-mass stars are cooler and less luminous than high-mass stars
A main-sequence star’s luminosity can directly inform us of
the rate at which it converts hydrogen to helium
On an H-R diagram, stellar radii
increase diagonally from the lower left to the upper right
How is the lifetime of a star related to its mass?
More massive stars live much shorter lives than less massive stars
Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?
spectral type M2, luminosity class I
What is the common trait of all main-sequence stars?
They generate energy through hydrogen fusion in their core.
Which star is the hottest star?
O
Which main-sequence star will have the shortest lifetime?
O
Which main-sequence star has the lowest mass?
M
An O-star has a hotter surface temperature than the Sun. Therefore, compared to the Sun,
its emission peaks in the blue part of the spectrum.
What is the approximate chemical composition (by mass) with which all stars are born?
Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
The total amount of power (in watts, for example) that a star radiates into space is called its
Lumosinity
According to the inverse square law of light, how will the apparent brightness of an object change if its
distance to us triples?
Its apparent brightness will decrease by a factor of 9.
Assuming that we can mesure the apparent brightness of a star, what does the inverse square law for light
allow us to do?
calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity
If Star A is closer to us than Star B, then Star A’s parallax angle is
larger than that of Star B
Star A has an apparent magnitude of3, and Star B has an apparent magnitude of S. Which star is brighter in our sky
Star A
Our Sun is a star of spectral type
G
36) Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring periodic Doppler shifts
spectroscopic binary
What can we infer, at least roughly, from a star’s luminosity class?
its size (radius)
What is a white dwarf?
the remains of a star that ran out of fuel for nuclear fusion
All stars are born with the same basic composition, yet stars can look quite different from one another.
Which two factors primarily determine the characteristics of a star?
its mass and its stage of life
Sirius is a star with spectral type A and Rigel is a star with spectral type B. What can we conclude?
Rigel has a higher surface temperature than Sirius.
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group represents starts that are cool and dim
D
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group
represents stars of the largest radit?
E
Mi
H
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entre main sequence while (C) and (d) represent only small parts of the main sequence. Which group start with largest radii
E
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group
represents stars that are extremely bright and emit most of their radiation as ultraviolet light?
C
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group
represents stars with the longest main-sequence lifetimes?
D
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents
the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group
represents stars fusing hvdrogen in their cores
A