IR Compendium: Background: Units
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Wavelengths in infrared astronomy are commonly expressed in microns = micrometers = µm. (this can also be abbreviated "um" in contexts where µ is not available.)
| 5000 Angstroms = 500 nm = 0.5 µm | Visible light |
| ~0.9 µm to 5 µm | Near-infrared |
| 5 µm to ~30 µm | Mid-infrared |
| 30 µm to ~350 µm | Far-infrared |
Brightnesses or flux densities are most likely to be given in Janskys (Jy) or mJy (milli-Jy) or µJy (micro Jy).
1 Jansky = 1 Jy = 10^(-26) Watts/m^2/Hz
Jy can be converted to magnitudes. (Magnitudes are rarely used in the mid- or far-infrared.)
Surface brightness is usually given in MJy/sr (Mega-Janskys per sterradian, =10^6 Jy/sr), or microJy/arcsec^2 (micro-Janskys per square arcsecond).
For more information, see:
