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 Sorry, Joe. Didn't mean to imply that you were wrong. It was obvious that
you were quoting someone but due to the way it was worded it occurred to me that someone might conclude that the pair is separated by 380 LY and that leads to an orbital period of 75,000 years.
I always enjoy your posts.
Kim
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy- bounces@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Sunday, May 17, 2009 10:44 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Albireo: a double star?
Hi, I only quoted the APOD caption -- not sure where they got the info! Thanks, Joe
--- On Sun, 5/17/09, Kim <kimharch@cut.net> wrote:
From: Kim <kimharch@cut.net> Subject: Re: [Utah-astronomy] Albireo: a double star? To: "'Utah Astronomy'" <utah-astronomy@mailman.xmission.com> Date: Sunday, May 17, 2009, 8:20 AM
Burnham's is indeed out of date., at least in this instance. I believe that Albireo's true binary nature was only confirmed in the past 20 years or so. As Joe posted in reply, the yellow primary is a spectroscopic binary, although I didn't know that before. I believe that the information that Joe provided is a bit misleading: Albireo is about 380 light years distant from Earth - that isn't the distance between the two components. Joe, did you find the separation given anywhere (in other than angular distance)?
Kim
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah- astronomy- bounces@mailman.xmission.com] On Behalf Of M Wilson Sent: Sunday, May 17, 2009 12:15 AM To: Utah astronomy blog Subject: [Utah-astronomy] Albireo: a double star?
I found this a few years ago in the 1978 edition of Burnham's (Burnbaum's) Celestial Handbook Vol. II, page 754, third paragraph:
"Albireo is believed to be a physical pair, although no evidence of ortibal motion has been detected since the first observations of F.G.W. Struve in 1832."
Most of us, including myself, have been telling the public for years that the two were gravitationally bound. Looks like the proof is lacking or is Burnham's is out-of-date?
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