---
title: "Reading a stellar wind"
description: "Follow photon momentum into a wind spectrum, analyze native IUE orders and replay conditional count inference."
canonical_url: "https://sandboxphysics.com/stories/stellar-winds/"
language: "en"
page_type: "story"
alternate_languages:
  zh-CN: "https://sandboxphysics.com/zh/stories/stellar-winds/"
last_modified: "2026-11-04"
---

Stellar winds

# Reading a stellar wind

Sandbox Physics · 2026-11-03

A dark blue trough and a bright red wing trace gas around a star. Follow the photons, learn the transfer, then test the assumptions against real ultraviolet spectra.

1. L1

   ## [How starlight pushes a stellar wind](https://sandboxphysics.com/stories/stellar-winds/why-starlight-drives-winds/)

   Resonant atoms receive momentum from light. Follow blue absorption and scattered emission to see how photons interact with an expanding stellar wind.

2. L1

   ## [How much momentum can light carry?](https://sandboxphysics.com/stories/stellar-winds/photon-momentum-and-wind-energy/)

   Calculate photon recoil, wind momentum and mechanical power, keeping single scattering, repeated interactions and photon tiring distinct.

3. L2

   ## [Resonance surfaces in an accelerating wind](https://sandboxphysics.com/stories/stellar-winds/resonance-surfaces-in-an-accelerating-wind/)

   Derive the projected gradient, Sobolev optical depth and scattering source, then calculate one stellar-disk ray and its contribution to a wind spectrum.

4. L3

   ## [What can one wind line determine?](https://sandboxphysics.com/stories/stellar-winds/what-a-wind-line-can-determine/)

   Infer from saved integer photons, derive the mass-flow and ion-opacity degeneracy, and test a proper two-parameter prior with independent repetitions.

5. L3

   ## [Replaying the IUE ultraviolet spectra of P Cygni](https://sandboxphysics.com/stories/stellar-winds/replay-p-cygni-iue-spectra/)

   Decode complete native IUE orders, retain quality gaps and continuum choices, then recompute a conditional isolated-line comparison.

6. L4

   ## [Clumps, velocity gaps and mass loss](https://sandboxphysics.com/stories/stellar-winds/clumps-velocity-gaps-and-mass-loss/)

   Follow line instability into microclumping and velocity porosity, then replay the Brands 2025 tables without confusing model degeneracy with stellar trends.

[Follow the flow and change the collecting aperture](https://sandboxphysics.com/labs/stellar-wind-p-cygni/)

## Sources and calculation scope

1. [Owocki2014, Theory of Winds from Hot, Luminous Massive Stars](https://arxiv.org/html/1409.2084v1)

   Pinned v1; section2 for CAK/Sobolev steady winds and sections3.1–3.4 for line instability, clumping, porosity and velocity gaps. Linked theory source; original is not redistributed.

2. [Lamers, Cerruti-Sola & Perinotto1987, the SEI line-profile method](https://adsabs.harvard.edu/pdf/1987ApJ...314..726L)

   ApJ314,726, sectionsII–V and equations4–10/14–19. Our local escape singlet and fixed-source finite-width test retain their separate approximations; no complete SEI/non-LTE solver is claimed.

3. [IUE NEWSIPS manual, high-dispersion MXHI format](https://archive.stsci.edu/iue/manual/newsips/node155.html)

   Native17-field binary rows, padded768-element vectors, one-based STARTPIX, vacuum heliocentric wavelengths, ABS\_CAL physical units and FN noise.

4. [IUE data-analysis FAQ](https://archive.stsci.edu/iue/faq.html)

   Questions13–15: reject nonzero quality flags for quantitative use; high-dispersion cosmic rays are not automatically removed; exposure alone does not define a noise weight.

5. [NIST magnesium energy levels](https://physics.nist.gov/PhysRefData/Handbook/Tables/magnesiumtable7.htm)

   MgII level wavenumbers35760.848/35669.298per centimetre yield laboratory vacuum2796.3543/2803.5315Angstrom. Laboratory rest and stellar systemic velocity are distinct.

6. [MAST original mission data use](https://archive.stsci.edu/publishing/data-use)

   Original NASA/ESA/UK IUE public mission products; fixed names, complete bytes and SHA remain in the standalone package with mission/STScI/MAST attribution.

7. [Brands, Backs, de Koter et al.2025, X-Shooting ULLYSES XII](https://arxiv.org/html/2503.14687v1)

   Pinned v1; sections3/5.3–5.5, Figures1/4/7 and Tables7/8. Twenty-five LMC O-type targets yield24parameter sets. Their model-conditional population/fitness results are external, not P Cygni measurements.

8. [Brands2025 Zenodo15044512 v1.1.1 tables](https://zenodo.org/records/15044512)

   CC-BY4 complete optical+UV and optical-only24-row tables plus original readme. FASTWIND10.6.0 is proprietary; no model archive or engine is redistributed.

9. [Standalone stellar-wind scientific reproduction](https://sandboxphysics.com/stories/stellar-winds/materials/stellar-wind-science.zip)

   Original small data, independent transfer/photon/force/finite-width references,197producer checks and a proper synthetic Poisson exercise. Fixed truths and prior-averaged coverage remain separate.