Beaconess: Laser Guide Star
Cosmology & the Sky arc, page 161 of 193. Back to The Pixelated Physics Universe
Who they are
Beaconess has one line, and says it often: “No star? make one at 90 km.”
Beaconess is a character of the Cosmology & the Sky arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
Laser guide stars excite mesospheric sodium at 589 nm at about 90 km altitude.
$$ \begin{gathered} E = \frac{hc}{\lambda} \\ \lambda_{\text{Na D}_2} \approx 589\ \text{nm} \;\Rightarrow\; E \approx 2.1\ \text{eV} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $E$ | photon energy | J |
| $h$ | Planck constant | J·s |
| $c$ | speed of light | m/s |
| $\lambda$ | wavelength | m |
Sources
- R. Foy & A. Labeyrie, A&A 152, L29 (1985)
- W. Happer et al., JOSA A 11, 263 (1994)
Crossovers
Beaconess meets Harmonel (Green Laser Frequency Doubling). Harmonel doubles infrared light to green in a nonlinear crystal. Beaconess needs sodium's yellow 589 nm light, and making it efficiently also uses nonlinear optics.
Beaconess meets Waistwyn (Gaussian Beam Rayleigh Range). Beaconess launches a laser beam to make an artificial guide star at about 90 km. Waistwyn's Gaussian-beam rules decide how big that beam spot is when it gets there.
Wear the lore
- Beaconess, the Laser-Star Maker Mug
- Related infographic poster: The Sodium Doublet – Plate 045 Physics Poster
Concept keywords: Laser Guide Star, Beaconess, Cosmology & the Sky, physics lore, Pixelated Physics