• Forestine – Lyman-alpha Forest physics T-shirt
  • Forestine – Lyman-alpha Forest physics T-shirt
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ForestineLyman-alpha Forest

Forestine – Lyman-alpha Forest Physics T-Shirt

$29.99 USD
$29.99 USD
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Color
White · Black
Size
S–5XL
Made
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How do you map gas you cannot see? Forestine’s quasar beam crosses the universe through hydrogen clouds. Each cloud absorbs at the Lyman-alpha wavelength, shifted by its own redshift, so the spectrum fills with a dense forest of absorption lines. Astronomers use the forest to trace the cosmic web of intergalactic gas. Pixel-art unisex tee; equation, symbols and sources in the physics panel below.

Color
Size

Size guideS–5XL · inches

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

Measurements in inches, ±1.5 in tolerance.

ShippingFree US

Free US shipping · $10 flat shipping outside the US. Printed to order for you.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Light from a distant quasar crosses billions of light years of thin intergalactic hydrogen on its way to us. Every cloud it passes absorbs at the Lyman-alpha line.

Because each cloud sits at a different distance, each has a different redshift, so the one line appears again and again at different wavelengths. The spectrum fills with a forest of absorption lines, first identified by Roger Lynds in 1971.

Forestine's arrow is the quasar's light. Every cloud leaves a line.

Equations

\[\lambda_{\text{obs}} = (1+z)\,\lambda_{\text{Ly}\alpha},\qquad \lambda_{\text{Ly}\alpha} \approx 121.567\ \text{nm}\]
SymbolMeaningUnit
\(\lambda_{\text{obs}}\) observed wavelength of an absorption line \(\mathrm{m}\)
\(z\) redshift of the hydrogen cloud that absorbs \(\mathrm{–}\)
\(\lambda_{\text{Ly}\alpha}\) rest wavelength of hydrogen's Lyman-alpha transition (n = 2 to 1) \(\mathrm{m}\)

Sources

  1. Rauch (1998) The Lyman Alpha Forest in the Spectra of Quasistellar Objects, Annu. Rev. Astron. Astrophys. 36, 267
  2. Lynds (1971) The Absorption-Line Spectrum of 4C 05.34, ApJ 164, L73
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Field notes

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