ALGOL FROM EARTH

From the Earth, Algol appears as the brightest eclipsing variable. Its period of variation, as stated before, is 2.867315 days. At this period, there is an eclipse in which Algol’s visual magnitude changes from 2.12m to 3.40m and remains about the same for 10 hours. At this point, Beta Persei B moves in front Beta Persei A. There is also a period when the B component is behind the A; the visual magnitude slightly drops, but can only be registered photometrically.

The angle of inclination of the plane of the orbit of the AB system as viewed from Earth appears to be 97.69°, but is increasing with 0.1° per century. The C component’s orbit is inclined with 83.98°.