Imaginary patterns of stars are called
constellations
What are five characteristics used to classify stars?
Color, temperature, brightness, constitution, and size
What reveals a star's surface temperature?
The color of the star reveals it
If a star's color is BLUE, is it hotter or cooler?
It is hotter
If a star's color is RED, is it hotter or cooler?
It is cooler
What does the brightness of a star depend on?
Temperature and size (absolute brightness), and its distance from earth (apparent brightness)
What is ABSOLUTE brightness?
How bright a star actually is
What is APPARENT brightness?
A star's brightness as seen from Earth
What is revealed by the red color of the supergiant star called Betelgeuse?
It is a fairly cool star
Stars that are much larger than the sun are called...
Supergiants
The amount of light a star gives off is called its...
Absolute brightness or luminosity
Luminosity is the same as:
Absolute brightness
Why does Rigel shine as brightly as Betelgeuse, even though Rigel is much smaller than Betelgeuse?
Rigel is very hot and each square meter of its photosphere gives off a lot of light, causing it to shine very brightly even at its small size.
What is a light-year?
The distance that light travels in one year (about 9.5 million kilometers)
True or False: The light year is a unit of time.
False because it is a measure of distance, not time
The diagram that shows the relationship between the surface temperatures of stars and their absolute brightness is called...
The Hertzsprung-Russell Diagram (H-R Diagram for short)
The area on the Hertzsprung Russell diagram that runs from the upper left to the lower right and includes more than 90% of all stars is called the...
Main Sequence
Circle the letter of each sentence that is TRUE based on the HR diagram in your textbook.
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. The sun is a main sequence star.
C. Rigel is hotter than Betelgeuse.
D. Polaris is brighter than the sun.
True or False: Forces on Earth are different from those elsewhere in the universe.
False
What is the law of universal gravitation?
It states that every object in the universe attracts every other object
What two factors determine the strength of the force of gravity between two objects?
The masses of the objects and the distance between them.