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Modelling motions of binary star system #4095

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henrysky
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I have added support to model motions of binary star system as seen on the sky and their 6D astrometry (RA, DEC, PMRA, PMDEC, PLX, RV).

So far I have only manually added Alpha Centauri A/B, Sirius A/B and 61 Cygni A/B. In order to model a binary system we need:

  • $e$ - Eccentricity
  • $a$ - Semi-major axis
  • $\Omega$ - Longitude of the ascending node
  • $\omega$ - Argument of periapsis
  • $i$ - Inclination
  • $P$ - Period
  • $T$ - Periastron epoch
  • Barycenter RA/DEC, PMRA/PMDEC, PLX, RV
  • Barycenter data epoch
  • HIP or Gaia ID of primary and secondary stars
  • Primary and secondary star masses

At least for Alpha Centauri A/B and Sirius A/B, the motion on the sky as well as radial velocity matched really well to past observations (https://iopscience.iop.org/article/10.3847/1538-3881/abfaff/pdf, https://arxiv.org/pdf/1703.10625).

If there are other binary systems you want to model, I can try to find all the required orbital parameters and add them manually before we figure it out a way to model a large amount of binary stars if possible.

Fixes #353

Screenshots (if appropriate):

An example of Sirius A/B with parallax disabled to avoid confusion:

Untitled.mov

Type of change

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • This change requires a documentation update
  • Housekeeping

How Has This Been Tested?

Test Configuration:

  • Operating system: MacOS 15.2
  • Graphics Card: Apple M3

Checklist:

  • My code follows the code style of this project.
  • I have performed a self-review of my own code
  • I have commented my code, particularly in hard-to-understand areas
  • I have made corresponding changes to the documentation (header file)
  • I have updated the respective chapter in the Stellarium User Guide
  • My changes generate no new warnings
  • I have added tests that prove my fix is effective or that my feature works
  • New and existing unit tests pass locally with my changes
  • Any dependent changes have been merged and published in downstream modules

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Great PR! Please pay attention to the following items before merging:

Files matching src/**/*.cpp:

  • Are possibly unused includes removed?

This is an automatically generated QA checklist based on modified files.

@gzotti
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gzotti commented Jan 23, 2025

Great stuff! But probably #4076 should be 100% fixed before adding this.

γ Vir is another nice double. For a catalog, this looks promising: http://www.astro.gsu.edu/wds/orb6.html

@alex-w
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alex-w commented Jan 23, 2025

Great stuff! But probably #4076 should be 100% fixed before adding this.

γ Vir is another nice double. For a catalog, this looks promising: http://www.astro.gsu.edu/wds/orb6.html

Damn, I don't have access to WDS catalog anymore O_o

Yes, adding full support WDS catalog is possible now and probably it should be adding via 2 files - one file for known orbital elements of binaries (multiple systems) and one file for cross identification and informational data (likewise a currect HIP subset of WDS).

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Binary Star : Mean Proper Motions and True Motions
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