Requests for a few systems

[Mneme]

I am working on a fictional atlas. Certain multiple star systems that I need to reference are beyond my skillz because I would like them to use semi-accurate orbital data. Would anyone with the skillz and knowledge of the relevant data sources be willing to build approximations of these systems?

Alcyone - 5
Alshain - 2
Antares - 2
Mira - 2
Polaris - 3
Rigel - 4

Also, if I have classes or orbital estimates wrong here could those be pointed out? http://f.tarazedi.com/viewtopic.php?f=18&t=187

Thank you in advance.

[ThinkerX]

For double star orbits, your best bet would be the 'Double Star Library' (should turn up on google).

If those systems have published orbits, that is where they will be.

Worth noting: At least some systems are optical (not true doubles)

[PlutonianEmpire]

For double star orbits, your best bet would be the 'Double Star Library' (should turn up on google).

If those systems have published orbits, that is where they will be.

Worth noting: At least some systems are optical (not true doubles)

Googling it produces multiple separate websites with the same name, as far as I can tell. How do we know which one is the one you're referring to?

[ThinkerX]

Sixth Catalog of Orbits of Visual Binaries (real catchy title). Basically all the double star orbits published. I made frequent use of it in my own project a few years ago, along with the WDS.

If memory serves, there are images of the orbits available as well.

http://www.usno.navy.mil/USNO/astrometr ... d/wds/orb6

From the same site, the 'Washington Double Star Catalog', the single most comprehensive published listing of double stars and relevant measures out there. Gives earliest and latest position angles and separations for almost every measured double star. Word of warning: This is a large catalog, updated frequently. I made frequent use of this catalog as well for my own project.

http://www.usno.navy.mil/USNO/astrometr ... d/wds/orb6

In both cases, I linked to the explanatory page prior to the catalog itself. I very strongly suggest reading these descriptions first, as these are technical catalogs.

Also, it would be a very good idea to dig up the Bayer/Flamesteed designations for the brighter systems, and DM catalogue numbers for the remainder. The 'orbit' catalog gives a variety of designations for each double, but this is not the case with the WDS (usually just the discoverers ID and the DM, and sometimes not even the DM).

Dated versions of both catalogs are available at Vizier, and I believe there is a visual plot option.

[Mneme]

I'm not making a whole lot of sense out of this; I was able to BS several of these but Alcyone is beyond me and I need that one. :\

[ThinkerX]

Ok...I went and did some digging in the depths of the WDS, Vizier, Simbad, and elsewhere.

First, the basics:

Alcyone = 25 Tau = HD 23630 = DM +23.00541 = WDS J03475+2406

The Hip parallax works out to a distance of 123.6 parsecs or 403 light years. Margin of error is within 10%, meaning this number is probably trustworthy.

Yale Bright Star says both the A and the B components are occulting or spectroscopic binaries, but I could not find any mentions as to duration. Probably on the order of days to weeks though.

All the measures in the WDS give very large angular separations for these stars (not the spectroscopic components). AB is given at about 117" with the position angle remaining constant. At the indicated distance from the Hip, that works out to a true separation of 0.23 *LIGHTYEARS*, or about 23% of a lightyear, far, far too much to be a binary, unless you allow for an orbital period measured in hundreds of thousands of years (very doubtful). The constant position angle does argue for common proper motion, though not an orbit. The separations for the other components are even worse; I'd go so far as to say those are mostly optical.

What this leaves you with is the A and B components taken separately, spectroscopic binaries which nobody has bothered to compute orbits for. There are a *LOT* of systems like this.

You can look up the numbers yourself. Go to 'Vizier' (should turn up on a google search).

In the lower search box, enter 'HD 23630'.

Most of the way down the page (might take a bit to load), you'll find 'Double Stars in Astrometric Catologs' by Wycoff. That gives the history of measures over a hundred plus years. (Wycoff is not the highest quality, but for this, its good enough).

Out of curiosity, what are you attempting to accomplish?

[Mneme]

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.

[ThinkerX]

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.

[ThinkerX]

Uhgg...

Polaris = Alpha Ursa Minor = HD 8890

Distance works out to around 132 parsecs or 430 light years.

I found a listing for Polaris proper as being a specroscopic binary with a an orbital period 6.8 years.

Additionally, there is an 'unresolved blue companion with an orbital period calculated at either 30.5 years or 27.6 years, and an eccentricity of around 0.6

AB are listed as physical, showing common proper motion, though the distance between them works out to around 2400 astronomical units.

********************************************************************
Rigel = Beta Orion = HD 34085

Distance from parallax works out to about 880 lightyears.

Rigel proper is a spectroscopic binary with a period of 9.86 days.

Rigel BC is physical with A, separation working out to around 2700 au. Probably common proper motion rather than an actual orbit.

Rigel BC is a very tight binary in its own right. Separation on the order of 27-28 astronomical units.

[ThinkerX]

Why did you choose these giant or supergiant stars ?
They are cooler and bigger than a little nice dwarf like sun.

I was wondering the same thing.

My interests are focused on dwarf stars from about F5V to M1V.

[ThinkerX]

Yep. Identifying stars that might host earthlike worlds was my goal.

There a few years ago, I made the same kind of research.
I limited myself to dwarf F7V class to K3V.
Before F7 is a bit too hot for life and beyond K3, there is too much lethal radiations for "life".
I kept it as single star or very far from their stars compagnions (more 200 AU).
And yet in this list you can find stars unstable or eruptive...

I went with Turnbull and Tarter. Their criteria started at F5 on the hot side, though this also had to do with the stars lifetime. It also ran right down into the M's. As to 'lethal radiations'...I don't think thats an issue except for flare stars and other variables. At least Turnbull and Tarter didn't believe so.

As to planets in binary systems, even tight ones...they predicted those, and Kepler found a couple.

But yes, there are many things that can knock a star meeting the other criteria right off the list: too young to have formed terrestial planets, too old and evolving into a subgiant, variable, radio star, certain types of binaries.

I started with the HYG catalog (a combination of the Hip and Gliese, pretty much). I ran some statistical checks on it, and noticed a *lot* of nearby stars were 'missing' from these lists, and not only that, some of these missing stars were probably a lot like the sun. So, to cut a long story short, I went searching for them.

[Mneme]

Thank you for your help, folks. I did what I could with Alcyone but I'm not satisfied with it. Rigel and Polaris were just guide stars so I removed them from consideration.

The mentality behind certain star choices is that there aren't a lot of habitable planets anyway and any civilization that is engaged in interstellar travel would have little problem with inhabiting an inhospitable system. There are also additional, purely fictional systems with habitable planets. I still have to make a lot of textures though.

If anyone is curious, an alpha of the atlas is found here:

http://f.tarazedi.com/viewtopic.php?f=18&t=207

The Tarazedi Atlas Downloader program is placed in the Celestia folder and run to retrieve the files from my repository. The downloader will overwrite asterisms.dat, start.cel, demo.cel, and splash.png and includes the 1 million stars.dat. The repository around 100 MB so far and is updated somewhat regularly hence the downloader rather than a zip file. The program I used to make the EXE is called Advanced Free BAT to EXE Converter. Be aware that the downloader shows up in AVG as a false positive (this is not an issue I expect to spend any energy on; c'est la vie).