Stromgren Edge is a hymn to photoionization—the way hot, young OB stars carve glowing cavities in space. Their ultraviolet light strips electrons from hydrogen, making vast H II regions that shine while ions and electrons continuously recombine. At the boundary, where the photon budget runs out, the ionization front turns razor-thin; dust and neutral gas throw long shadows, birthing pillars and trunks.

[INTRO — whispered, pulse drone]
Strömgren, Strömgren… edge of the light…
Case B, case B… count every night…

[CHORUS]
U.V. from O.B., carving a sea,
Hydrogen’s singing at ten to the four K.
Edges where GAMMA falls, bright H two walls,
Recombine, cool, and the rims all blaze.

[CHORUS — repeat, softer]
UV from OB, carving a sea,
Hydrogen’s singing at ten to the four K.
Edges where GAMMA falls, bright H TWO walls,
Recombine, cool, and the rims all blaze.

[VERSE 1 — “OB STAR” voice]
I am the Lyman-continuum flood,
photons at thirteen point six and above.
Sigma (H one) high, I cut through the haze,
till neutral builds up and I’m turned away.

[VERSE 2 — “CLOUD” voice]
I am the column, dust in my veins,
N_H rising, I swallow the flames.
(TAU (mu) climbs; e-to-the-power-of-negative-Tau shuts the door,)
GAMMA as a function radius drops and I’m neutral once more.

[REFRAIN — chant, minimalist]
Gamma times n-H-zero… equals…
alpha-B n-e n-p.
(Gamma n-H-zero) = (alpha-B n-e n-p).

[VERSE 3]
n_e, n_p, in balance they lie,
H-alpha, Oxygen Three the lines testify.
U = Phi over N lightspeed, how hard is the field?
Push on the skin till the front has to yield.

[PRE-CHORUS]
Dust sets the color, grain cross-section small,
FUV’s a sculptor in Lyman–Werner halls.
PDR’s the halfway house of night and day—
C⁺ humming warm while H₂ slips away.

[CHORUS]
UV from OB, carving a sea,
Hydrogen’s singing at ten to the four K.
Edges where GAMMA falls, bright H two walls,
Recombine, cool, and the rims all blaze.

[VERSE 4 — “GEOMETRY” voice]
R_S to the third, from Q₀ you’re born,
(three over four pi alpha Beta N squared.
Inside: ionized, isothermal morn;
Outside: thin shell where the photons are torn.

[BRIDGE — whispered call & response]
Saha whispers “LTE?” — not here, not now.
(Too thin, too cold, too few collisions to allow.)
Baker and Menzel say “Case B, be kind,”
Skip to the ladder and leave ground state behind.

[VERSE 5]
OB associations, young and blue,
Sigma Orionis paints the curtain I.C. 434 through.
Pillars stand stubborn where columns run deep,
Elephant trunks where the shadows keep.

[REFRAIN — layered round]
Gamma n-H-zero… alpha-B n-e n-p…
Photo in, recomb out, steady state on repeat…
Gamma n-H-zero… alpha-B n-e n-p…

[CHORUS — wide, airy]
UV from OB, carving a sea,
Hydrogen’s singing at ten to the four K.
Edges where Γ falls, bright H II walls,
Recombine, cool, and the rims all blaze.

[OUTRO — thinning to a whisper]
When the star burns out, fronts drift and fade,
Electrons find protons in the dark we’ve made.
Cycle turns over in the long-wave night—
Neutral, then kindled, then shadow, then light.