Quiz 4 Flashcards
Approximately what basic composition are all stars born with
Three quarters hydrogen, one quarter helium, no more than 2 percent heavier elements
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ
Mass they are formed with
What are the standard units for luminosity
Watts
A stars luminosity is the
Total amount of light that the Star radiates each second
What are the standard units for apparent brightness
Watts per square meter
If the distance between us and a Star is doubled, with everything else remaining constant the luminosity will…
Remain the same but the apparent brightness is decreased by a factor of four
Why do astronomers often measure the visible light apparent brightness instead of the total apparent brightness of a Star
In order to measure the total apparent brightness of a Star you must measure its brightness in all wavelengths and this is difficult to do. The only wavelengths you can measure from the surface of earth are visible and radio wavelengths
Suppose you measure the parallax angle for a particular star to be 0.1 arc seconds the distance to this Star is
10 parsecs
The most distant stars we can measure stellar parallax for are approximately
100 parsecs away
Which of the following statements about the apparent and absolute magnitude is true
A star with apparent magnitude 1 is brighter than other with apparent magnitude 2
A stars absolute magnitude is the apparent magnitude it would have it it were at a distance of 10 parsecs from earth
The absolute magnitude of a Star is another measure of its luminosity
The magnitude system that we see now is based on a system used by the ancient Greeks over 2,000 years ago that classified staff by how bright they appear
The spectral sequence sorts stars according to
Surface temperature
Th spectral sequence in order of decreasing temp is
OBAFGKM
Oh but a fart good kill me
Why is the spectral sequence of stars not alphabetical
The original alphabetical labeling did not correspond to surface temperatures and thus had to be reordered
Which of the following statements about spectral types of stars is true
The spectral type of a Star CJ’s be used to determine it’s surface temp
The spectral tote of a Star can be used to determine its color
A star with spectral type a is cooler than a star with spectral type b
A star with spectral type F2 is hotter than a star with type F3
Suppose you see two main sequence stars of the same spectral type. 1 Star is dinner in apparent brightness than Star 2 by a factor of 100 what can you conclude
Star 1 is 10 times more distant than Star 2
Which of the following terms is given to a pair of stars that appear to change positions in the sky indicating that they are orbiting one another?
Visual binary
Which of the following terms is given to a pair of stars that can we can determine are orbiting each other only by measuring their periodic Doppler shifts
Spectroscopic binary
On a HR diagram where would we find stars that are cool and dim
Lower right
On a HR diagram where would we find stars that are cool but luminous
Upper right
On a HR diagram wheee would we find stars that have the largest radii
Upper right
On a HR diagram where would we find white dwarfs
Lower left
On a HR diagram where would we find red giant stars
Upper right
You observe a Star in the disk of a Milky Way and you want to plot the star on an HR diagram you will need to determine all of the following
Apparent brightness
Spectral type
Distance to the Star
On the main sequence stars obtain their energy
By converting hydrogen into helium
