BPASS-in-Browser
Visualise stellar evolution in your browser.
bib is an accessible, configurable interface to the released BPASS stellar-population models. Explore a spectrum, photometry and the other population tables in the browser, or fetch the same numbers through the API.
Loaded releases include BPASS v2.2.1 and the v2.3 α-enhanced grid. The data are licensed CC BY-NC 4.0.
What is BPASS?
The Binary Population and Spectral Synthesis code, by J. J. Eldridge (University of Auckland) and E. R. Stanway (University of Warwick), predicts what populations of stars look like as they age — their spectra, colours, ionizing output, supernova rates and chemical yields. Its defining feature is that it follows binary stellar evolution in detail: most massive stars have a companion close enough to interact, and those interactions reshape a population's light in ways single-star models miss. See the tutorial for a gentle introduction, or go straight to the official v2.2 user manual.
In this interface
- Tutorial
- What an SSP is, what the IMF and metallicity labels mean, and how binaries change the light.
- SSP Explorer
- Spectrum, star counts, supernova rates and ionizing output of one simple stellar population, from 1 Myr to 100 Gyr. A second population can be pinned for comparison. Photometry gives AB magnitudes in the bundled filters, or in a transmission curve you upload.
- Fetch data
- Download an SED, photometry, or the other population tables for a chosen IMF, metallicity and age.
- Data and API
- What is loaded on this server, and the same numbers as JSON from
/api/v1(interactive docs).
Scripted or large-scale analysis
For work across the full BPASS grids — population synthesis, colour–magnitude diagrams,
event rates — use
hoki
(Stevance, Eldridge & Stanway 2020),
the BPASS manuals and the release papers.
Install hoki with pip install hoki and cite it with those papers.
Acknowledging BPASS
BPASS is developed and released on a best-effort basis by a small team. If anything you produce with this tool ends up in a paper, talk or classroom, please include the official acknowledgement and cite the release papers:
This work made use of v2.2.1 of the Binary Population and Spectral Synthesis (BPASS) models as described in Eldridge, Stanway et al. (2017) and Stanway & Eldridge (2018).
This work made use of v2.3 of the Binary Population and Spectral Synthesis (BPASS) models as described in Byrne et al. (2022) and Stanway & Eldridge (2018).
Papers to cite
- Eldridge, Stanway et al. (2017), Binary Population and Spectral Synthesis Version 2.0, PASA, 34, e058 — ADS · DOI
- Stanway & Eldridge (2018), Re-evaluating old stellar populations, MNRAS, 479, 75 — ADS · DOI
- Byrne et al. (2022), Dependence of stellar population spectra on α-element enhancement (v2.3), MNRAS, 512, 5329 — ADS · DOI
Licence
BPASS data products are released by the BPASS team under CC BY-NC 4.0 (attribution, non-commercial). This site does not redistribute the release files. bib itself is open source under the MIT licence . Bundled filter curves come from the Spanish Virtual Observatory Filter Profile Service — cite Rodrigo, Solano & Bayo (2012) and Rodrigo & Solano (2020) if the filter set matters to the work.
Built with
FastAPI, SQLAlchemy and PostgreSQL on the back end; Plotly.js, htmx and Alpine.js on the front end; numpy and astropy for the science core, with dust laws via the dust_extinction package. First built with frontier generative-AI models and human verification in late 2026. Please report bugs — especially wrong numbers — as you would for any research tool.
We count page views and country so we can tell if the tool is used. Privacy.