What is a standard candle?
A)an object for which we are likely to know the true luminosity
B)an object for which we can easily measure the apparent brightness
C)a class of objects in astronomy that all have exactly the same luminosity
D)any star for which we know the exact apparent brightness
E)a long,tapered candle that lights easily

Question

Quizplus · Accepted Answer

A standard candle is an object for which we are likely to know the true luminosity. This allows us to use the difference between the observed brightness and the known luminosity to determine the distance to the object. Examples of standard candles include Type Ia supernovae and certain types of variable stars.

Answer: B
 A standard candle is also an object for which we can easily measure the apparent brightness. By comparing the apparent brightness of the object to its known luminosity, we can determine the distance to the object. However, it is more common to use standard candles based on known luminosity rather than easily measurable apparent brightness.

Answer: C
 While some classes of objects in astronomy may have similar or even identical luminosities, they are not considered standard candles unless we can reliably use their luminosity to measure distances. Examples of classes of objects with similar luminosities include main sequence stars of similar mass and age, although these are not commonly used as standard candles.

Answer: D and E
 Neither D nor E accurately describe a standard candle. While we can use the calculated true luminosity or easily measured apparent brightness of an object to determine its distance, this does not make it a standard candle. And, a long, tapered candle is not relevant to astronomy or the concept of standard candles.

What Is a Standard Candle