So basically even if a system is identified as being, say, a 5-star system, these are just quick-and-dirty assumptions someone's made by glancing at the catalog info and I shouldn't worry about them? That would make life easier. LOL Thank you for going over the info; I'll see what to do about it next time I work on this.
Not quite.
Long ago, astronomers noted the presence of companions to Alcyone.
The question becomes are these companions close in reality, or merely close visually? (An optical illusion of sorts.)
Now...keeping the above in mind...
There are different types of binary systems.
There are systems where the stars orbit so close together they cannot be visually separated. In some of these systems the stars are about the same size and luminosity; in others one star is say...a hundred or a thousand times more luminous than the companion. These are typically called 'occulting' or 'spectroscopic' binaries; astronomers know they are there because the total light output fluxuates when one passes in front of the other. *The A and B components of Alcyone fall into this catagory.*
There are many binary systems where the stars orbit each other (or one around the other) at distances that work out to actual separations of a few astronomical units to a few dozen or even a few hundred astronomical units. Rule of thumb here: Pluto in our solar system is about 40 au off and takes better than a couple centuries to make one orbit. Hence, orbital periods of decades or centuries are the norm here. Worth noting, most multiple systems - including the specroscopic/occulting ones - have high degrees of orbital eccentricity, often better than 30%. (apart from Pluto, I don't believe any object in our solar system has an eccentricity greater than 2 or 3 percent).
Then you have 'common proper motion' stars. These are stars separted by at least a few hundred au (frequently thousands of au, and sometimes a light year or more) that happen to be moving in the same direction at the same speed. Even the closer ones don't really orbit, instead they...'fish tale', a sort of pendulumn type motion. This is the catagory the A and B components of Alcyone appear to fall into (and probably some of the others. The ones that don't are optical.).
I based my conclusion (couldn't find anything definitive in the literature) on the relatively constant 'Position Angle' and 'Angular Separation', along with the dates (years) those measures were taken.
For 'Position Angle', envision a circle drawn around one of the stars, marked off in degrees. Hence 360 degrees.
The 'Angular Separation' gives the distance between the stars, in seconds of an arc. (take the circle, divide it into 24 equal 'hours', divide each hour into 60 equal 'minutes', and divide each minute into 60 equal 'seconds'. For parallax work this goes down to ten thousandths of a second, but 'seconds' is good enough for most double star work).
Combined, these two elements form a coordinate system. With the dates (years) you can see what happens over time.
If, over a period of at least decades, the PA and AS remain fairly constant, then that argues for the systems sharing common proper motion, depending on the degree of angular separation. If the PA and AS diverge radically over time, that indicates an optical (false) system, UNLESS the angular separation is very small AND the divergence could be fitted into some sort of orbital scheme. Note that professional astronomers sometimes disagree on this; I have seen orbits calculated for systems by one set of astronomers declared optical by others.
Also worth keeping in mind: many if not most binaries we see from earth are seen almost 'edge on' or 'tilted' from our POV. Hence, the observations would show tiny shifts in the PA on one side of the star with differences in the AS (say a PA of 10 to 30) followed by a repeat on the other side of the star (PA 190 to 220).
Any thoughts about Polaris and Rigel?
I suppose I could take a look sometime.
My objective is to have an "Orion's Arm"-like encyclopedia with Celestia add-ons for my own writing, if you're familiar with them.So basically even if a system is identified as being, say, a 5-star system, these are just quick-and-dirty assumptions someone's made by glancing at the catalog info and I shouldn't worry about them? That would make life easier. LOL Thank you for going over the info; I'll see what to do about it next time I work on this.
Any thoughts about Polaris and Rigel?
My objective is to have an "Orion's Arm"-like encyclopedia with Celestia add-ons for my own writing, if you're familiar with them.
My past project became a Celestia add-on, though likely a minor one.
I was attempting an updated repeat of Tarter and Turnbull's 'Habcat II') - the expanded SETI target list. What they attempted was a sort of rough count of main sequence (dwarf) stars of F5 down to around M1 using the Tycho catalogue as a base, stars *NOT* found in the Hip. They claimed something like a couple hundred thousand possibles ranging out to a few hundred parsecs.
I used the ASCC (essentially an update of Tycho) and a spectroscpic - photometric distance system of my own devising to compute distances to around 33,000 FGK stars with a margin of error hovering around 20%. (I tended to think of it as being accurate to within 20% about 70 - 80% of the time). Along the way, I tracked down a great deal of info on the double stars within that set.
For what its worth, even the HIP, the best extant distance catalog (and the base for Celestia) has a lot of parallax issues. If my hazy memory serves, something on the order of half the stars in the Hip have parallaxes off by more than 20%, meaning you can't put a great deal of faith in those particular determinations.
About six months ago, I ran a series of callibrations to update my system, making it purely photometric (not dependant on knowing the spectral type in advance). The tests were promising, but I'll have to run more checks before proceding with an update. This is something I intend to spend a few weeks on this winter.