Quote:
Originally Posted by ngcles
Hi Trevor & Dennis,
Dennis, the one you refer to (and have imaged) is mentioned in Hartung as the "companion" to Zeta Orionis (Alnitak) with the close seperation of 2.5". In my First Edition it is Object No 188 within the list, though Hartung does not cite any designation from a recognised catalogue for it. It is also recorded in my circa 1973 Nortons and has no designation there either. Is there one? Is there anybody out there with a latest edition Hartung that may contain additional info on a catalogue?
The one Trevor has imaged is the "companion" GSC4771:1207 -- which is also Σ774 (Struve 774) which is sep by 57.6" in PA 10 essentially unchanged in 100 years according to a cursory search (have I mentioned before how much I hate the SIMBAD interface).
A quick look at Dennis's image confirms it is indeed GSC4771:1207 (Σ774 B) with apparently the correct PA, magnitude and sep.
In the blurb Dennis posted, the "companion" there is refered to as being 3" distant (ie just like Hartung & Nortons) and is therefore quite likely gravitationally bound to Alnitak -- as noted. The one Trevor imaged is almost certainly not a gravitationally bound companion -- at a distance of 800-odd ly even assuming they are at the same distance, 58 arc-seconds equates to ... way too far away -- several light-years I'd think (couldn't be bothered to do the maths this time of night -- someone else can do it) !
So I reckon you are both right -- in the sense that both are recognised "companions" to Zeta Orionis. The one imaged by Trevor is not the one in the blurb -- but it is in a recognised catalogue. The one imaged by Dennis does not appear to be in a catalogue, but is likely physically bound to Alnitak.
Best,
Les D
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Thanks for your investigation and report Les, so many stars, so much data; I was almost ready to throw my Mewlon out when I saw how easily Trevor had split Alnitak.
In the current Hartung (2nd Ed Marlin & Frew) I think this is listed as Object 215 (P310), a “brilliant white pair” and I think that this description refers to Trevor’s image rather than the closer companion in my image.
Cheers
Dennis