It would be interesting to know for sure as Albeio is a frequent and favorite star staple and we get a lot of questions about it. My astronomy software lists it as a binary and to Erick's point most of what I was able to find lists it as a true binary system as well although the distance was more often reported as 380 ly vs. 400 ly. Not a significant distance unless you were heading there soon. Robert Taylor -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of erikhansen@TheBlueZone.net Sent: Sunday, May 17, 2009 1:23 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Albireo: a double star?
My 2 cents. I compiled a list of 25 famous double stars some years back, as I recall Deep Sky and Sky&Telescope were my primary sources. I may have gotten some info from Burnham. For Alberio I have it listed as 400 LY from earth and a separation of 34.3 Astronomical Units. I have only Zeta Hercules (12 AU) and Alula Australis (20 AU) as closer, although I don't have AU separation for 7 on the list, I assume that means they are further apart than AU's can be applied. IE: They are only optical doubles. Those are Delta Herc, Sigma Cor Bor, Almach, Porrima, Alpha Sag, Al Rischa, and Delta Lyra. That indicates to me that they are a gravitational pair. Does anyone know the AU threshold for gravitational double stars? For instance I have Epsilon Persei at 2000 AU's. BTW: Rob our our fellow SLAS'ers behaving themselves in Hawaii? Erik