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Table 4
Additional allowed units.
| Quantity | Unit | Meaning | Notes | |
|
|
||||
| plane angle | deg | degree of arc | π / 180 rad | |
| arcmin | minute of arc | 1 / 60 deg | ||
| arcsec | second of arc | 1 / 3600 deg | ||
| mas | milli-second of arc | 1 / 3 600 000 deg | ||
| time | min | minute | 60 s | |
| h | hour | 60 min = 3600 s | ||
| d | day | 86 400 s | ||
| † | a | year (Julian) | 31 557 600 s (365.25 d), peta a (Pa) forbidden | |
| † | yr | year (Julian) | a is IAU-style | |
| energy* | † | eV | electron volt | 1.6021765 × 10-19 J |
| ‡ | erg | erg | 10-7 J | |
| Ry | rydberg |  eV |
||
| mass* | solMass | solar mass | 1.9891 × 1030 kg | |
| u | unified atomic mass unit | 1.6605387 × 10-27 kg | ||
| luminosity | solLum | solar luminosity | 3.8268 × 1026 W | |
| length | ‡ | Angstrom | angstrom | 10-10 m |
| solRad | solar radius | 6.9599 × 108 m | ||
| AU | astronomical unit | 1.49598 × 1011 m | ||
| lyr | light year | 9.460730 × 1015 m | ||
| † | pc | parsec | 3.0857 × 1016 m | |
| events | count | count | ||
| ct | count | |||
| photon | photon | |||
| ph | photon | |||
| flux density | † | Jy | jansky | 10-26 W m-2 Hz-1 |
| † | mag | (stellar) magnitude | ||
| † | R | rayleigh | 1010 / (4π) photons m-2 s-1 sr-1 | |
| magnetic field | †‡ | G | gauss | 10-4 T |
| area | pixel | (image/detector) pixel | ||
| pix | (image/detector) pixel | |||
| †‡ | barn | barn | 10-28 m2 | |
| Miscellaneous units | ||||
| D | debye |  C.m |
||
| Sun | relative to Sun | e.g., abundances | ||
| chan | (detector) channel | |||
| bin | numerous applications | (including the 1-d analogue of pixel) | ||
| voxel | 3-d analogue of pixel | |||
| † | bit | binary information unit | ||
| † | byte | (computer) byte | 8 bit | |
| adu | Analog-to-digital converter | |||
| beam | beam area of observation | as in Jy/beam | ||
Notes.
(‡)
Deprecated in IAU Style Manual (McNally 1988) but still in use.
(*)
Conversion factors from CODATA Internationally recommended values of the fundamental physical constants 2002 (http://physics.nist.gov/cuu/Constants/).
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