Cepheid variable stars vary because they have reached a point in their evolution

Question

Cepheid variable stars vary because

they have reached a point in their evolution where absolute magnitude varies over a period of time .

the distance to them varies as Earth orbits the Sun.

there are clouds in interstellar space that move across them .

they have companion stars that orbit them causing changes in luminosity.

2 points   

QUESTION 2

Cepheid variables are valuable as distance markers because they are ________ and their period of brightening is directly related to their ________________

bright; absolute magnitude

bright; apparent magnitude

dim; apparent magnitude

dim; absolute magnitude

2 points   

QUESTION 3

Cepheid variable stars are main sequence stars

True

False

2 points   

QUESTION 4

Cepheid variable stars can be used to measure distance to galaxies.

True

False

2 points   

QUESTION 5

In order to determine whether or not a star is a Cepheid variable I will need to measure____________ in lab.

period of variability and apparent magnitude

absolute and apparent magnitude

distance and absolute magnitude

period of variability and apparent magnitude

they have reached a point in their evolution where absolute magnitude varies over a period of time .

the distance to them varies as Earth orbits the Sun.

there are clouds in interstellar space that move across them .

they have companion stars that orbit them causing changes in luminosity.

Explanation / Answer

they have reached a point in their evolution where absolute magnitude varies over a period of time.
Cepheid stars are variable because they pulsate in and out.

bright; apparent magnitude. Measuring their apparent luminosity allows a straightforward calculation of their distance.

False. All stars, late in their lifetime, change from being average stars for their mass ( main sequence stars ) to becoming swollen red giants . Most stars change from the swollen red giant phase to pulsating variable stars before they finally die. thus Cephie stars are yellow stars.

True. Cepheid variable stars can be used to measure larger distances such as the distances between galaxies

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