But binary eclipses usually occur every few days and last only hours, a far cry from the years-long activity of Epsilon Aurigae. And what of that surprising mid-eclipse peak in brightness? Some astronomers currently theorize Epsilon Aurigae may be a binary system where the companion star brings with it a huge accretion disk of dust and gas, blocking the main star's light (the hole in the disk would account for the peak). Other models put two stars within that disk, making the whole thing a trinary system. Recent observations also suggest ongoing changes within the system, as might be consistent with a red giant evolving to a white dwarf.
This is one of the few genuine mysteries left to us in the galaxy, and it might be changing before our eyes. "[It's happening] on a time scale of decades rather than centuries or millions of years," said Robert Stencel of the University of Denver. Each eclipse happens a little differently, so we never really know what to expect. This year's observations might provide all the answers, or just leave us with new questions.
That's why the amateur astronomers are so essential. "If we have people in Canada or Finland watching this thing during the high summer," Stencel said, "they might be able to help us fill in some blanks." So observers of the northern latitudes take note: Astronomers need you to help figure out Epsilon Aurigae's mystery. With any luck, we'll have it all figured out by next time, in 2036. And if not, well, we're getting used to that.
Be sure to check a closer look at Epsilon Aurigae by Robert Zimmerman in Astronomy's October issue
, on newsstands September 1.