Celestia Forums

In standard Celestia, Castor is only represented as a single star.
In fact Castor is a sextuple star system made of three binaries, bright visual stars Castor Aab and Bab and dim red flare stars YY Geminorum AB, which are much brighter in X-ray wavelengths, all orbiting each other in a complex dance.

Detailed descriptions of the system(s) are here: http://www.solstation.com/stars2/castor6.htm

Here is a first draft of the system based on the descriptions at the above site: Obsolete
You can download the updated version here: my later post on page 2 of this thread.
(I've only modeled the orbital dynamics and elements of the system -- no fancy features, such as flares you might expect to see in the YY Geminorum pair)

Not all orbital elements are well known (on that web-site) so I have calculated missing data from other known or estimated values.
(eg. SemiMajorAxis information has not been provided in all cases, so some of those are calculated from known or estimated mass-ratio's).

Please feel free to check my calcs (and the underlying assumptions) and let me know if you have any issues.


Overview of the system with the AabBab system at top right, and the Cab system (YY Geminorum) at the left:
(These orbit each other about every 10,000 years)
celURL: 20,000,000,000 x faster



Zoom in closer on the AabBab barycenter -- the Bab system is at the top, and the Aab system at the bottom:
(orbital period = 467 years)
celURL: 1,000,000,000 x faster


let's take a closer look at the Aab system to see the individual stars Aa and Ab:
(orbital period = 9.21 days)
celURL: 100,000 x faster


and likewise for the Bab system (Ba and Bb):
(orbital period = 2.93 days)
celURL: 100,000 x faster


and then zoom in on the Cab (YY Geminorum) system to see the 2 red (M) dwarf flare stars:
(orbital period = 19.536 hours !! )
celURL: 10,000 x faster

Can someone tell me is there a way to get Celestia to display the greek special characters, when the source of information is an STC file?
STC catalogs drop all special formatting when saved, so I've had to resort to using "alf".

The stars.dat version displays the greek character, but my STC version will not.

Chuft-Captain wrote:Can someone tell me is there a way to get Celestia to display the greek special characters, when the source of information is an STC file?
STC catalogs drop all special formatting when saved, so I've had to resort to using "alf".

The stars.dat version displays the greek character, but my STC version will not.

I think that all you need to do is capitalize the alf: ALF

--Chris

Thanks Chis,

I'll try that.

PS. I've also found another source of data, which appears to be more comprehensive wrt Castor: http://www.stellar-database.com/Scripts ... ame=castor

Do you have an opinion on which is the better source of information, this or the other site: http://www.solstation.com/stars2/castor6.htm

CC

chris wrote:I think that all you need to do is capitalize the alf: ALF

Works a treat! Thanks Chris

I forgot to mention...

There's a minor issue with the labelling of these multiple systems (due to the components being so close to each other).

As you zoom out, at a certain point, the star labels of a binary pair begin to overlap completely:

EDIT: In the picture above, if you look closely there's actually 6 labels displayed, 2 overlapping labels at each binary (Castor-Aa & Castor-Ab; Castor-Aa & Castor-Ab; and Castor-Aa & Castor-Ab) although you can really only see the b-version at each site because they're overlapping) :


This is probably a situation which only affects complex systems containing close binary pairs such as Castor, so it's probably a rare situation.

However, if you're a perfectionist, you might like to consider a solution which replaces star labels with the barycenter name as this begins to occur. EDIT: ie. IMO, at this level of zoom, the pairs of labels should be superseded by the label of the respective parent object

(I think this will be an issue in some of the more complex spacecraft models as well...( eg. my O'Neills). The solution in this situation may be less obvious, so a solution which is good for all situations may require some more thought.

Sorry, one more issue Chris.

I wanted to add the following line to each of the 6 Star definitions:


This seems to be ignored and instead it tries to go to the SINBAD site with an invalid HIP number (because I don't have one for these particular stars):
eg.
Cb goes to: http://simbad3.u-strasbg.fr/sim-id.pl?p ... P268434909
Ca goes to: http://simbad3.u-strasbg.fr/sim-id.pl?p ... P268434910

This gives an error page with the message: " This identifier is not correctly written..."

Is it a feature that InfoURL's on Stars always go to SINBAD? (It happens for Sol as well: http://simbad3.u-strasbg.fr/sim-id.pl?p ... Ident=HIP0 )

If so, then I need to either override this behaviour with a different site, as I tried to do with the InfoURL (that would be my preference), or I need to at the very least provide a valid HIP number as the Ident parameter in the http call to the SINBAD site.

Any advice?

The InfoURL isn't working for stars. This is one feature I already asked before (it's in the bugs tracker list). Currently, the stars InfoURL is hard coded and can't be changed, which is an inconsistency with the rest (since we can add an InfoURL to any other object).

Chris, can we have custom InfoURL for stars as well, which should overwrite the hard coded one ?

Cham wrote:The InfoURL isn't working for stars. This is one feature I already asked before (it's in the bugs tracker list). Currently, the stars InfoURL is hard coded and can't be changed, which is an inconsistency with the rest (since we can add an InfoURL to any other object).

Chris, can we have custom InfoURL for stars as well, which should overwrite the hard coded one ?

Thanks Cham. Thought that might be the case.

Cham wrote:The InfoURL isn't working for stars. This is one feature I already asked before (it's in the bugs tracker list). Currently, the stars InfoURL is hard coded and can't be changed, which is an inconsistency with the rest (since we can add an InfoURL to any other object).

Chris, can we have custom InfoURL for stars as well, which should overwrite the hard coded one ?

Yes, there's no reason other than time not to do it. If someone else wants a small coding project, all that needs to be done is to add a string (pointer, since it will usually be NULL) to the StarDetails object and then modify the parser in stardb.cpp.

--Chris

I was just thinking about the labeling issue above...

One approach that might work is: while traversing the structure consider the angle subtended onscreen by siblings when determining which labels should be displayed, (preecedence given to higher levels, child labels only displayed if the separation is great enough. (I'm assuming the structure is already traversed somewhere in the code, so it's just a matter of finding the right place to do this test)

eg. The structure of this group of stars is:



so:
Castor would be the label displayed by default.
If the separation of any of the children of Castor is large enough, then display the children's labels instead of the parent ... continue down each branch of the tree stopping when separation of any of the siblings is too small.

EDIT: This strategy may not be suitable for spacecraft models, where in most cases I suspect you would not want the placeholders to be labeled at all. However, there will exceptions to this rule as well)

Chuft, your images server make the page slow to load...

Cheers Fenerit,

Sitesled seems to be down at the moment (All these free servers seem to have periodic problems). I'll try to move the images to another server and/or convert them to thumbs.

CC

Chuft, the addon looks good and I've tried to download the stc but I'm having difficulty the server times out.

Sitesled seems to be back in action, so you should be good to go now Derek.
Give it another try.

CC

Using the 2 million star database, another star is present, TYC 1282-3359-0, which I assume to be equivalent to Castor B. If one uses that database, seven stars are present, with this seventh star not orbiting anything.

There's a quick fix to that.
Change the designation of the dimmer star by giving it a HIP number corresponding to the TYC of the star.

TYC aaaa-bbbbb-c becomes cbbbbbaaaa

Examples
TYC 2825-3358-0-> HIP 033582825.
TYC 197-37-1-> HIP 1000370197.

Thus, in this case, TYC 1282-3359-0 -> HIP 033591282
If done correctly, this will override the TYC star.

Another thing, the stars shouldn't have lower case designations. "Castor Ab" is used to represent a planet orbiting Castor A. Castor AB (capitalized) represents a stellar companion.

Also Castor BB doesn't seem right. It's an M2V star, but the Vmag given indicates a luminosity of 1.93 x Solar.

It's a very great add-on, by the way, thank-you so much for making it! I have a lot of interest in multiple star systems.

Thanks Hungry,
I'm glad you like the addon.

I have a slightly different approach to the Tycho star:
What's needed is to stop it shining as a star and also prevent it's label from popping up anywhere near the Castor Barycenter's location.
So let's make it a Barycenter instead of a star, and put it somewhere "out of the way". (In my interstellar dumping ground ):

What I recommend is that anyone using this addon in conjunction with the 1million, 2million star databases should put the above piece of code in the STC (or in a separate STC in the Castor folder.

Hungry4info wrote:Another thing, the stars shouldn't have lower case designations. "Castor Ab" is used to represent a planet orbiting Castor A. Castor AB (capitalized) represents a stellar companion.

You should read this: http://redalyc.uaemex.mx/redalyc/pdf/571/57102124.pdf

Hungry4info wrote:Also Castor BB doesn't seem right. It's an M2V star, but the Vmag given indicates a luminosity of 1.93 x Solar.

I've used arbitary Appmag values for now, (it's still a draft addon ). Once I've discovered the appropriate appmags for each star the luminosity values should be more accurate.
A lot of other aspects of the addon are assigned approximate or arbitrary values (eg. SMA, Inclination, AscendingNode, ArgOfPericenter, MeanAnomaly).
Some of these are simply not known because of the difficulty of measuring them. (Even getting an accurate measurement of distance is not easy).
As yet, I haven't specified Epoch's, which really should be done for the longer period orbits if it's known.

Thanks for the feedback.
CC

Chuft-Captain wrote:Thanks Hungry,
I'm glad you like the addon.

I have a slightly different approach to the Tycho star:
What's needed is to stop it shining as a star and also prevent it's label from popping up anywhere near the Castor Barycenter's location.
So let's make it a Barycenter instead of a star, and put it somewhere "out of the way". (In my interstellar dumping ground ):

Code: Select all

 Barycenter 0033591282 "Disabled"
 {
 RA         0
 Dec          0
 Distance     100000
 }


What I recommend is that anyone using this addon in conjunction with the 1million, 2million star databases should put the above piece of code in the STC (or in a separate STC in the Castor folder.

Hungry4info wrote:Another thing, the stars shouldn't have lower case designations. "Castor Ab" is used to represent a planet orbiting Castor A. Castor AB (capitalized) represents a stellar companion.

You should read this: http://redalyc.uaemex.mx/redalyc/pdf/571/57102124.pdf

Hungry4info wrote:Also Castor BB doesn't seem right. It's an M2V star, but the Vmag given indicates a luminosity of 1.93 x Solar.

I've used arbitary Appmag values for now, (it's still a draft addon ). Once I've discovered the appropriate appmags for each star the luminosity values should be more accurate.
A lot of other aspects of the addon are assigned approximate or arbitrary values (eg. SMA, Inclination, AscendingNode, ArgOfPericenter, MeanAnomaly).
Some of these are simply not known because of the difficulty of measuring them. (Even getting an accurate measurement of distance is not easy).
As yet, I haven't specified Epoch's, which really should be done for the longer period orbits if it's known.

Thanks for the feedback.
CC

Didn't think about making a barycenter.

Reiko wrote:Didn't think about making a barycenter.

That's just to make it invisible. There's probably other ways to achieve this, that's just the method that seemed most obvious to me. A bit of a hack, but better than having doubled up stars.

Chuft-Captain wrote:

Reiko wrote:Didn't think about making a barycenter.

That's just to make it invisible. There's probably other ways to achieve this, that's just the method that seemed most obvious to me. A bit of a hack, but better than having doubled up stars.

I just made another star with the same name and put it 16,000 ly away. It didn't make a double or anything.