A Method of Categorizing Double Stars

[daedalus1]

I wrote this journal article for the Journal of Double Star Observers, but I have no idea whether they will publish it or not. I sent it a few days ago, and have not heard whether is was received, let alone correctly submitted.

In any event, it is written and submitted, so I can probably provide a copy here for our club.

Thanks,

Tony

[Pete]

Wow! Couldn't agree more with your approach Tony. But can't imagine viewing with an exit pupil of only 0.33mm. That's not just small, it's so tiny that I didn't realize the eye could process it.

[daedalus1]

Yeah, Pete, an exit pupil of 0.33mm is pretty small.

My resolution magnification (remember, this is for point sources only) has an exit pupil of 0.2mm. Floaters are bigger than that! But enough information gets to my brain for evaluation of the target star most of the time. I operate almost always at 200x (0.75 mm ep) for initial study and evaluation, and 450x (0.33 mm ep) for measurement. No problems at all there with evaluation.

The problem, when increasing power/decreasing field of view is finding and centering the target. I must increase in steps and use wide field centering techniques to actually find the target at such high magnifications. After the initial evaluation, I'll use a 25mm cross hair eyepiece with a 3x barlow and center the star, then switch to 450x. With a little practice and pre-focusing data, I was able to overcome any difficulty.

[mark.m]

Tony:
Fascinating!

Your selection criteria sorts stars into three "candidate" categories. Is there a way to promote a star from "candidate" status to "confirmed"? (For example, if a pair has been observed through half a complete orbit, it should be possible to promote it to "confirmed", right? Is there a way to promote a star using your separation and motion parameters?)

- Mark

[daedalus1]

Good morning, Mark,

To answer that, one must first define a "binary star system" aka binary or double star. "Astronomy Today", Chaisson and McMillan, 2005 defines "binary star systems, which consists of two stars in orbit about a common center of mass, held together by their mutual center of attraction." MacEvoy adds to that by further stipulating that the system must last for the life of the stars.

So, how do you figure that out?

To answer whether a star system is a true binary as opposed to a "candidate" at the very least it must have a calculated orbit. You have to calculate an orbit based on historical data, that is, position angle and separation, then determine if it is likely that that orbit will last for the life of the stars. Even then, the calculated orbits have a hierarchy of accuracy, or "grades": 1 being most accurate and 9 being least. Relative proper motion and escape velocity are also included in the final determination, but not everyone agrees with that. I guess it really depends on who you talk to.

To answer whether my method can be used to promote a star from candidate to confirmed, the answer is no. My method has nothing to do with orbital determination, other than to note that there is or is not an orbit noted in the Washington Double Star catalog. My method takes advantage of pre-existing data and compiles it for the amateur or educator who wants to further study a star system. My system may keep them from wasting their time on an optical double, or one that may not meet their research goals.

There are no catalogs of double stars that give any indication of physicality other than the "Stelle Doppie" website, which uses only relative proper motion to indicate physicality. But that is not nearly definitive. The WDS lists many stars that have orbits, but many more that could have orbits. That is what I want to show.