Exam 2 Flashcards
What information can astronomers learn from the spectrum of a star?
They can determine the element, the temperature, and density of the star
What makes the spectrum of each chemical element (and molecule) unique?
- Every element is built differently
- every element has a unique structure of electron orbital levels
- For each element there is a maximum number of energy levels
What are the two main types of optical (visible light) telescopes? What do they use to collect
light?
REFRACTING TELESCOPES: uses lenses to collect and focus light (limit to how big it can be made)
REFLECTING TELESCOPES: uses mirrors to collect and focus light (modern telescopes; newton invented)
How do telescopes improve our view of the universe?
LIGHT GATHERING: gathers more light and makes faint objects appear brighter (telescope that’s twice as big gathers x4 more light)
RESOLUTION: ability to see fine details in smaller objects (bigger telescopes have higher resolution)
What are the advantages to putting astronomical observatories on mountain tops? What
conditions would make for the best observing sites?
Better views on mountains
Location, no light pollution, dark skies (essential), weather (clean and dry air), atmosphere and seeing (smearing of image of earth turbulence) are big factors for best observing sites
What are the advantages to putting telescopes in space? What are the disadvantages?
- no bad weather or seeing
- Can observe 24/7
- No light pollution (sky is darker)
- can see all types of light
What is the difference between brightness and luminosity? When you see a star in the night sky,
do your eyes see its brightness or its luminosity
LUMINOSITY: The amount of energy radiated by a star each second
BRIGHTNESS: The amount of energy radiated by a star that is received by an observer at a distance
in the night sky you would see the brightness (how it appears from earth)
What is apparent magnitude? How does the magnitude scale work
APPARENT MAGNITUDE: How bright an object appears to an observer on earth
- scaled from 1 to 6 magnitude (how visible it is to observer)
- smaller numbers = brightest (1:bright ,, 6:faint)

Why did Hipparchus make the scale so that smaller numbers are brighter
The closer the star is to us the brighter it’s magnitude will be
A 2nd magnitude star is how much brighter than a 3rd magnitude star? A star that has an
apparent magnitude that is five magnitudes lower than another one is how many times
brighter?
2.5 = 1 magnitude to the next magnitude
100 = a star that is lower/higher by 5 magnitudes
What are the factors that determine the apparent magnitude of a star?
- Distance and luminosity
- blue stars are more luminous than red

What factors determine the luminosity of a star?
Brightness and distance
If we know the luminosity and temperature of a star, what other property can be determined?
What is the relationship between the three factors?
Size?
How does the Sun’s size compare to that of other stars?
It is an average size star
- there are stars that are 100 times larger or smaller
What is a binary star?
Two or more stars that orbit around a common center of mass
- Formed together as a group; gravitationally bound together
