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24 Cards in this Set

  • Front
  • Back
A cluster of stars, gases, and dust held together by gravity is called a(n)______.
galaxy
What is the universe?
All of space and everything in it.
Most of the universe is _________.
empty space
Why don't scientists measure distances to stare in Kilometers?
Distances to stars are so large that the Kilometer is not a very practical unit.
What is a light-year?
The distance that light travels in one year, or about 9.5 million million Kilometers.
True or false?
THe light-year is a unit of time.
false
What is parallax?
The apparent change in position of an object when you look at it from different positions.
Which one of these is what astronomers use parallax to measure the distance to.
a)distant stars
b)the Sun
c)the planets
d)nearby stars
d)nearby stars
To measure parallax shift,astronomers look at the same star twice, when Earth is on different sides of the ____.
Sun
What are the three main characteristics used to describe stars?
a.size
b. temperature
c.brightness
Stars that are much larger than the Sun are called ______.
giant stars or supergiant stars
WHich kinds of stars are smaller than the sun?
a. neutron star
b. giant star
c. supergiant star
d. white dwarf star
a. neutron star
d. white dwarf star
What reveals a star's temperature?
Its color
What is revealed by the red color of the supergiant star called Betelgeuse?
a. it is an extremely hot star
b. it is in a constellation
c. it is far away
d. it is a cool star
d. it is a cool star
THe amount of light a star gives off is called its _________.
brightness
WHy does Rigel shine as brightly as Betelgeuse, even though Rigel is much smaller than Betelgeuse?
Rigel is very hot, so it gives off a lot of light.
How bright a star looks from Earth depends on what two factors?
a. How far the star is from Earth
b. How bright the star actually is
What are the 2 measurements of brightness and their definitions?
a. Apparent magnitude- a star's brightness as seen from Earth
b. Absolute magnitude- the brightness a star would have if it were a standard distance from Earth
True or false? THe closer a star is to Earth, the brighter it is.
false
What two things must an astronomer find out in order to calculate a star's absolute magnitude?
a. the star's apparent magnitude
b. the star's distance from Earth
THe diagram that shows the relationship between the surface temperature and the brightness of stars is called the _________.
Hertzsprung- Russel Diagram
WHat is measured on the x- and y- axes of the H-R Diagram?
x-axis- surface temperature (C)
y-axis- brightness
An area on the H-R Diagram that runs from the upper left to the lower right and includes more than 90 percent of stars is called the ___________.
main sequence
Which of these is true based on the H-R diagram?
a. THe sun is a main- sequence star
b. white dwarfs are brighter than supergiants
c. Rigel is hotter than Betelgeuse
d.Polaris is brighter than the Sun
a, c, d