One of the three stars of the Goat, which belongs to the remarkable eclipsing variable stars of the Algol type. It consists of a bright white giant, 37,000 times more luminous than the Sun, and a dark companion, which is not visually observable. Both stars are in mutual orbit. Every 27 years - 9,883 days - the dark component passes in front of the giant and obscures a large part of its light, causing the star ε Aur to significantly darken in the sky - from 3.1 magnitude to 3.8 magnitude. This dimming lasts for several months - about 190 days, then the star remains at a minimum for about half a year, and in the next 190 days it grows from the minimum to the maximum. This suggests that the companion must be surrounded by a dark cloud of gas and dust. The last such eclipse occurred in 2009. Among the known eclipsing variables, it exhibits one of the longest periods.