To an astronomer,what is a "standard candle"?
A) A standard light source that can be placed in a telescope,to which the brightnesses of stars and other objects can be compared
B) Any type of object whose absolute magnitude is known
C) Any galaxy whose redshift has been measured accurately
D) An accurately defined brightness scale for stars and galaxies,such as the magnitude scale

Question

Quizplus · Accepted Answer

A "standard candle" is any astronomical object of known luminosity (absolute magnitude), which can be used to determine distances to other similar objects using their apparent brightness (apparent magnitude). This is based on the inverse square law of radiation, which states that the apparent brightness of an object decreases with the square of the distance from the observer. By comparing the apparent and absolute magnitudes of standard candles, astronomers can calculate how far away other objects are. Examples of standard candles include Cepheid variables, supernovae, and certain types of stars and galaxies. Choice A is incorrect because a standard candle is not a specific light source that can be placed in a telescope, but rather a concept used for distance determination. Choice C is incorrect because redshift is a measure of an object's velocity relative to the observer, not its luminosity. Choice D is incorrect because the magnitude scale is a relative measure of brightness, not an accurately defined scale for standard candles.

To an Astronomer,what Is a "Standard Candle