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Introduction:

We seem to know a lot about Epsilon Aurigae, however, some of the new data has changed what we thought we knew. The following poses question about the star system. Some of the answer are known with great confidence while others with less or little confidence. With the 2009-2011 eclipse hopefully we will have new data to help add new pieces to the puzzle and help solve the mystery.

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Star System:

How do we know how far the star system is from us?
How do we know the system's period?
How do we know the distance between the components?
How do we know how fast the components are moving around the center of mass?
How do we know the direction the components are rotating?
What causes the out-of-eclipse variations?
What causes the mid-eclipse brightening?
What causes the hydrogen alpha line horns?
What causes the very large sodium D absorption lines?

Main Star:

How do we know the star is an F star?
How do we know its mass?
How do we know its diameter?

 

Eclipsing Body:

How do we know there is a second component?
How do we know its mass?
How do we know its diameter?
How do we know its thickness?
How do we know how fast the eclipsing body is rotating?
How do we know the direction the body is rotating?
How do we know the diameter of the central transparency?