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Epsilon Aurigae, the Mystery Star in Auriga the Charioteer

February evenings show off Epsilon Aurigae, the distant and mysterious star in the constellation Auriga the Charioteer. To find Epsilon Aurigae (otherwise known as Almaaz), look first for the bright beacon star Capella, the brightest in the constellation Auriga. As seen from our mid-northern latitudes, Capella shines high overhead at about 9:00 p.m. local time in early February, 8:00 p.m. mid-February, and 7:00 p.m. late February and early March. Look nearby Capella for a small yet prominent triangle of starlets called The Kids. Lighting up the apex of this triangle is our feature star, Epsilon Aurigae.
photo of Epsilon Aurigae
The photo on the right is from Computer Science Geek's photostream (some rights reserved), courtesy of fickr.com. This is a view of the western evening sky as it appears in late winter and early spring. The brilliant star Capella is a bit to the right of dead center, with the fainter star Epsilon Aurigae appearing immediately below Capella. For a sky chart showing Epsilon Aurigae and the constellation Auriga high overhead in the February evening sky, click here.
Although Capella looks much brighter than Epsilon, that's because Capella is so much closer. Capella resides about 42 light-years away, whereas Epsilon is probably over 2,000 light-years distant. If this yellow supergiant star were as close as Capella, it'd outshine Capella by some 150 times. Depending on the source of information, the diameter of Epsilon Aurigae is 1 to 2 astronomical units (Earth-sun distances) across.
In cycles of 27 years, the light from Epsilon Aurigae dims for a period of two years. Epsilon Aurigae is an eclipsing binary star, whereby the "dark" star routinely eclipses the visible star. This star last dimmed in 1982-1984. According to Professor Robert Stencel, Epsilon Aurigae is to dim again, starting in August 2009, and is to be totally eclipsed by December 21, 2009. Mid-eclipse is expected to occur in August 2010.
The dark body in this binary sytem might be a star that's enshrouded in a large disk of dust. But nobody knows for sure. Astronomers will be intently studying Epsilon Aurigae during its 2009-2011 dimming to see if they can unlock the secret of this mystery star.

copyright 2009 by Bruce McClure

Sky Chart Showing Epsilon Aurigae

Comet Lulin Sky Map for February

January 2009 Feature * March 2009 Feature