Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
Compared to the sun most nearby stars are... |
...Less luminous and smaller |
|
|
Compared to a star with mass equal to the mass of the sun, a main sequence star of 10 solar masses is... |
...hotter and more luminous. |
|
|
What is plotted on an H-R diagram? |
Luminosity versus surface temperature |
|
|
Compared to a main sequence star of type O, a main sequence star of type K is... |
...Cooler and less massive |
|
|
True or False:
Star A appears brighter than Star B as seen from Earth. Therefore, Star A must be closer to Earth than Star B. |
False |
|
|
From a distance of 1 parsec, the angular size of Earth's orbit would be... |
2 arc seconds |
|
|
Stars of spectral class M do not show strong lines of hydrogen in their spectra because... |
...Their surfaces are so cool that most hydrogen is in the ground state. |
|
|
Stars with cool surfaces can be very luminous if they are what? |
Large |
|
|
The mass of a star may be determined.. |
...only if it is in a binary system. |
|
|
True or False: |
False |
|
|
What type of star is the sun? |
G |
|
|
About what fraction of stars are on the main sequence? |
More than 90% |
|
|
If the sun had a hotter surface would it be redder or bluer or the same color? |
Bluer. |
|
|
Who invented the magnitude scale and classified stars by brightness? |
Hipparchus |
|
|
About what fraction of stars are in binary systems? |
1/2 |
|
|
Which star has a white dwarf companion? |
Sirius |
|
|
Stars of which spectral type have the coolest surface? |
M |
|
|
Stars of which spectral type have the hottest surface? |
O |
|
|
Which characteristics need to be measured in order to determine the luminosity of a star? |
Apparent brightness and distance |
|
|
Once the luminosity of a star is known what has to be measured in order to find the star's radius? |
Color (to find the surface temperature) |
|
|
List the spectral types in order from the type having the strongest hydrogen lines to the type having the weakest hydrogen lines. |
A, B, F, G, K, M, O |
|
|
List the spectral types in order from hottest surface temperatures to coolest surface temperatures. |
O, B, A, F, G, K, M |
|
|
Match the binary system to a feature of that system.
1. Visual binary 2. spectroscopic binary 3. eclipsing binary
____One detects the system by seeing periodic doppler shifts in its light-absorption lines shift back and forth as stars move. |
Spectroscopic binary |
|
|
Match the binary system to a feature of that system.
1. visual 2. spectroscopic 3. eclipsing
____In this kind of binary, by studying the way the light varies during each orbit, it is possible to estimate not only the star's masses, but also their radii. |
Eclipsing binary |
|
|
Most of the 100 stars that appear brightest in the night sky are... |
More luminous and larger than the sun. |
|
|
What do you need to measure in order to find the distance to a star by what is called spectroscopic parallax? |
The star's apparent brightness and spectral type |
|
|
Describe how one measures how fast stars are moving in a transverse direction. Suppose the distance to the star has already been measured. |
One uses a telescope to actually watch the change in the position of the star relative to more distant stars. |
|
|
Compared to a star with equal mass to the mass of the sun, a main sequence star of .5 solar masses would be |
Cooler and less luminous. |
|
|
If the sun had a cooler surface it would be |
Redder |
|
|
Compared to the main sequence star of type G, a main sequence star of type B is |
Hotter and more massive |
|
|
Compared to stars with cooler surfaces, stars with hot surfaces emit light with |
Shorter average wavelength |
|
|
What are the two physical characteristics of stars that are related by an H-R diagram |
Brightness and surface temperature |
