The star Algol in the constellation Perseus has these unusual characteristics. Every 68.75 hours its brightness dims suddenly from apparent magnitude 2.3 to apparent magnitude 3.5 and remains there for a few hours before returning just as suddenly to 2.3. In addition, halfway through this 68.75-hour period, the apparent magnitude becomes slightly dimmer than 2.3 for a few hours and then returns to 2.3. From this information alone it is possible to classify Algol as a(n)
A) optical double.
B) eclipsing binary.
C) totally eclipsing binary.
D) partially eclipsing binary.

Question

Quizplus · Accepted Answer

Algol's periodic dimming and brightening is characteristic of an eclipsing binary system, where one star passes in front of the other from our viewpoint, causing the observed brightness to decrease. The brief period of dimming halfway through the cycle suggests the secondary eclipse when the dimmer star is eclipsed by the brighter one.

The Star Algol in the Constellation Perseus Has These Unusual