From the page: “Epsilon Aurigae Star System
The epsilon Aurigae system is among the most interesting eclipsing star systems. It has puzzled astronomers for nearly 200 years. It is a bright star (3rd magnitude) located about 3 degrees southwest of Capella and eclipses once every 27.1 years. It is at the vertex of a triangular group of stars known as “The Kids”. Zeta Aurigae, another interesting long-period eclipsing binary, makes up one of the other two stars.
What makes this star system so intriguing is not just its long period but the length of its eclipse, what happens during the eclipse and what happens out-of-eclipse. The eclipse lasts nearly two years which with the 27.1 year period means the eclipsing body must be gigantic. There have been no satisfactory explanations for this. To make matters even more interesting, there seems to be a mid-eclipse brightening. How can this be? One explanation, according to James Kemp, is that the eclipsing body is a giant cloud of gas enclosing two small stars in orbit around each other. These stars sweep out an area in the middle. It would be a bit like a giant donut. This donut must be tilted such that as it eclipses the primary star, the system’s total light decreases and the “donut-hole” allows some of the primary star’s light to sneak through at mid-eclipse.”