ChromaStar
Author: Ian Short
Description: Model stellar atmosphere and spectrum and planetary habitable zone
Keywords: stellar atmosphere, stellar spectrum, spectral line, stellar parameters, stellar physics, stellar astronomy, astronomy teaching, astronomy education, stellar spectroscopy, stellar photometry, spectral classification, planetary habitable zone, life zone, extra-solar planets, exo-planets, greenhouse effect, albedo, climate science, environmental science, HTML graphics, HTML plotting, JavaScript graphics, JavaScript plotting, Saint Mary's University, Saint Mary's Astronomy and Physics Department, Institute for Computational Astrophysics, ICA

## ChromaStar (formerly "GrayStar")

##### Reliably responsive in Chrome, Opera, and sometimes Edge browsers under Windows

OpenStar pedagogical star and planet modeling in JavaScript. Visualization in HTML5. Hover for tips. Ctrl +/- to zoom

### Input:

#### Show/Hide stellar

Stellar parameters

Effective temperature, Teff (3400 - 50000) K) | Log10 surface gravity, log(g) (0.0 - 5.5 cm s-2 = dynes g-1) | Stellar mass (0.1 - 20.0 MSun) | Metal content (log10 0.001 - 10.0 x solar)
κFudge log10 mass extinction (-2.0 - 2.0 log cm2 g-1) | [He/Fe] (-1 - 1) | [C/O] (-2 - 2) | [α/Fe] (-0.5 - 0.5)

#### Show/Hide habitable zone

Habitable Planet Zone parameters

Surf pressure (0.6 - 22000 kPa) | Greenhouse effect, ΔT (-200 - +600 K) | Albedo (0.0 - 0.95)
Organic solvent
Water | Methane | Ammonia | Carbon dioxide

#### Show/Hide spectral line

2-level atom: Spectral line parameters

Line center wavelength, λ0 (350 - 1000 nm)
Line strength:
A12 Number density (2.0 - 11.0) | Log10 Oscillator strength, log f , (-6.0 - +1.0) | Ionization stage | Stage I ground ionization E, χI (eV ) (4.0 - 25.0) | Stage II ground ionization E, χII( eV ) (5.0 - 55.0) | Stage III ground ionization E, χIII( eV ) (5.0 - 55.0) | Stage IV ground ionization E, χIV( eV ) (5.0 - 55.0) | Excitation E, χl ( eV ) (0 - χI)
Stage I ground statistical wght, g1 (unitless) (1 - 100) | Stage II ground statistical wght, g2 (unitless) (1 - 100) | Stage III ground statistical wght, g3 (unitless) (1 - 100) | Stage IV ground statistical wght, g4 (unitless) (1 - 100) | Lower E-level statistical wght, gL (unitless) (1 - 100)
Line width:
Microturbulence, ξ T , (0.0 - 4.0 km s-1) | Particle mass (1 - 60 amu) | Log10 Broadening enhancement, γExtra (0.0 - 1.0) | vMacro (0 - 8 km s-1) | vRot (0 - 20 km s-1) | iRot (0 - 90 o)

#### Show/Hide samples

Sample pre-sets

Sample standard stars
User parameters | Sun | Vega | Regulus | Arcturus | Procyon | Planet hosts | 51 Pegasi | 61 Cygni A | Proxima Centauri | Fomalhaut
Sample worlds
User parameters | Earth | Venus | Mars | Titan
Sample Fraunhofer and classification spectral lines
User parameters | Na I D1 | Na I D2 | Mg I b1 | Ca II K | Ca II H | Ca I 4227 | Fe I 4045 | Fe I 4271 | He I 4471 | He I 4387

#### Show/Hide performance/realism

Modeling realism vs performance

ONLY update spectral line | No. HSE-EOS-Opac iters | No. Pe-IonEquil-MolecEquil iters | TiO bands (C3Δ-X3Δ, c1Φ-a1Δ, A3Φ-X3Δ)

### Output:

Narrow band Gaussian filter λ (270 - 2550 nm) σ (0.01 - 10 nm)
Plots: Atmosphere
Chem Eq (if Atmos plots ON) Radiation field 2-level atom: spectral line
Detailed print-out (below graphs): None Atmospheric structure Flux spectral energy distribution (SED) Specific intensity distribution High resolution spectral line profile Limb darkening coeffs Chem Eq (See Plot section menu)