Review                                                          Hubble Law

 

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

1)  Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately

A) 100 million.

B) 100 billion.

C) 1 billion.

D) 1 trillion.

E) 10 billion.

 

 

2)  Why are Cepheid variables important?

A) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements.

B) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future.

C) Cepheids are a type of young galaxy that helps us understand how galaxies form.

D) Cepheid variables are stars that vary in brightness because they harbor a black hole.

 

 

3)  What is a standard candle?

A) an object for which we can easily measure the apparent brightness

B) a long, tapered candle that lights easily

C) an object for which we are likely to know the true luminosity

D) a class of objects in astronomy that all have exactly the same luminosity

E) any star for which we know the exact apparent brightness

 

 

4)  How did Edwin Hubble measure the distance to the Andromeda Galaxy?

A) He applied the period-luminosity relation to Cepheid variables.

B) He used white dwarf supernovae.

C) He deduced it from its redshift.

D) He used main-sequence fitting.

E) He measured its parallax.

 

 

5)  What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe?

A) velocity and temperature

B) velocity and distance

C) luminosity and distance

D) luminosity and temperature

E) age and distance

 

 

6)  What is Hubble's law?

A) The faster a spiral galaxy's rotation speed, the less luminous it is.

B) The recession velocity of a galaxy is directly proportional to its distance from us.

C) The recession velocity of a galaxy is inversely proportional to its distance from us.

D) The faster a spiral galaxy's rotation speed, the more luminous it is.

E) The longer the time period between peaks in brightness, the greater the luminosity of the Cepheid variable star.

 

 

7)  Which of the following is a consequence of Hubble's Law?

A) more distant galaxies appear younger

B) the Big Bang

C) the closer a galaxy is to us, the faster it moves away from us

D) the more distant a galaxy is from us, the faster it moves away from us

E) all galaxies are moving away from us equally fast

 

 

 

 

 

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

1)  B

 

 

2)  A

 

 

3)  C

 

 

4)  A

 

 

5)  B

 

 

6)  B

 

 

7)  D