Hello world! Welcome to the documentation for orbitize, a Python package for fitting orbits of directly imaged planets.

orbitize packages two back-end algorithms into a consistent API. It’s written to be fast, extensible, and easy-to-use. The tutorials below will walk you through the code and introduce some technical stuff, but we suggest learning about the Orbits for the Impatient (OFTI) algorithm and MCMC algorithms (we use this one) before diving in. Our contributor guidelines document will point you to more useful resources.

orbitize is designed to meet the needs of the exoplanet imaging community, and we encourage community involvement. If you find a bug, want to request a feature, etc. please create an issue on GitHub.

orbitize is patterned after and inspired by radvel.


If you use orbitize in your work, please cite our forthcoming paper and the following DOI:


If you use the OFTI algorithm, please also cite Blunt et al (2017).


orbitize is under active development, and we’ve still got a lot to do! To get involved, check out our contributor guidelines, look over our issues list, and/or reach out to Sarah. We’d love to have you on our team!

Some major planned updates:
  • fit orbits of multiple objects in one system

  • fit Gaia astrometry & RVs

  • marginalize over instrumental uncertainties


1.4.0 (2019-7-15)

  • API change to lay the groundwork for dynamical mass calculation.

  • JeffreysPrior -> LogUniformPrior

  • New tutorials.

  • Added some informative error messages for input tables.

  • Bugfixes.

1.3.1 (2019-6-19)

  • Bugfix for RA/Dec inputs to the OFTI sampler (Issue #108).

1.3.0 (2019-6-4)

  • Add ability to customize date of tau definition.

  • Sampler now saves choice of tau reference with results.

  • Default tau value is now Jan 1, 2020.

  • Small bugfixes.

1.2.0 (2019-3-21)

  • Remove unnecessary astropy date warnings.

  • Add custom likelihood function.

  • Add progress bar for ptemcee sampler.

  • Add customizable color axis for orbit plots.

  • Small bugfixes.

1.1.0 (2019-1-6)

  • Add sep/PA panels to orbit plot.

  • GaussianPrior now operates on only positive numbers by default.

1.0.2 (2018-12-4)

  • Expand input reading functionality.

  • Bugfixes for MCMC.

1.0.1 (2018-11-20)

  • Bugfix for building on CentOS machines.

1.0.0 (2018-10-30)

  • Initial release.