Epsilon Aurigae, also known as Almaaz, is a super-giant F0 star in the constellation Auriga. This star is truly massive, being 100 to 200 times the diameter of the sun and 50,000 time more luminous. What is slightly unusual about this star is that every 27 years it’s light dims for a period of about 2 years and it’s considered that this is caused by the star being occulted by a companion object. The current cycle began back in August and once a week I’ve been taking a picture of it along with two adjacent bright stars as comparisons.
The results for 2009 are summarised in this graph:
My choice of comparison stars is not ideal as they themselves may be slightly variable so for future observations I’m including the star which is more usually used (lamda Aurigae) in my images. Global-Rent-A-Scope also upgraded the camera on this telescope at the end of December so I’m currently waiting for some updated calibration frames.
The graph is showing a nearly linear decrease in magnitude which is due to reach it’s minimum very soon. The nature of the companion object is currently under investigation and the present theory is that it is a large dust disk. Hopefully, the results from the study of this occultation will solve this mystery.