Conversion of Absolute Magnitude to Diameter

The following table lists the diameters of minor planets corresponding to the given values of the absolute magnitude, H. The diameter is to be read as kilometers when H is in the left-hand column, meters when in the middle column or millimeters when in the right-hand column. E.g., for a rocky body, H = 8.0 corresponds to a probable diameter range of 65 to 150 km , whereas H = 23.0 corresponds to a probable diameter range of 65 to 150 m. For icy bodies, the corresponding probable diameter ranges are 45 to 150 km and 45 to 150 m.

Conversion of H to a diameter for a specific object requires knowledge of the object's albedo. This quantity is not known for most objects, so the diameters listed here are given as ranges: the smallest value corresponding to an albedo of 0.5 (intended for icy objects), the middle value corresponding to an albedo of 0.25 and the larger to an albedo of 0.05. Most main-belt minor planet will have albedos in the range 0.05 to 0.25. If a specific object has an albedo < 0.05, the diameter will be larger than the upper limit listed here.


       Table: Probable diameter ranges for various
              H values and albedo values.

            H             Albedo            H     H
                   0.50    0.25    0.05
           -2.0    4700 -  6700 - 14900    13.0  28.0
           -1.5    3700 -  5300 - 11800    13.5  28.5
           -1.0    3000 -  4200 -  9400    14.0  29.0
           -0.5    2400 -  3300 -  7500    14.5  29.5
            0.0    1900 -  2600 -  5900    15.0  30.0
            0.5    1500 -  2100 -  4700    15.5  30.5
            1.0    1200 -  1700 -  3700    16.0  31.0
            1.5     940 -  1300 -  3000    16.5  31.5
            2.0     750 -  1050 -  2400    17.0  32.0
            2.5     590 -   840 -  1900    17.5  32.5
            3.0     470 -   670 -  1500    18.0  33.0
            3.5     370 -   530 -  1200    18.5  33.5
            4.0     300 -   420 -   940    19.0  34.0
            4.5     240 -   330 -   740    19.5  34.5
            5.0     190 -   260 -   590    20.0  35.0
            5.5     150 -   210 -   470    20.5  35.5
            6.0     120 -   170 -   370    21.0  36.0
            6.5      95 -   130 -   300    21.5  36.5
            7.0      75 -   110 -   240    22.0  37.0
            7.5      60 -    85 -   190    22.5  37.5
            8.0      45 -    65 -   150    23.0  38.0
            8.5      40 -    50 -   120    23.5  38.5
            9.0      30 -    40 -    95    24.0  39.0
            9.5      25 -    35 -    75    24.5  39.5
           10.0      19 -    25 -    60    25.0  40.0
           10.5      15 -    20 -    50    25.5  40.5
           11.0      12 -    17 -    37    26.0  41.0
           11.5       9 -    13 -    30    26.5  41.5
           12.0       7 -    11 -    24    27.0  42.0
           12.5       6 -     8 -    19    27.5  42.5
           13.0       5 -     7 -    15    28.0  43.0
           13.5       4 -     5 -    12    28.5  43.5
           14.0       3 -     4 -     9    29.0  44.0
           14.5       2 -     3 -     7    29.5  44.5
           15.0       2 -     3 -     6    30.0  45.0
           15.5       1 -     2 -     5    30.5  45.5
           16.0       1 -     2 -     4    31.0  46.0
           16.5       1 -     1 -     3    31.5  46.5
           17.0       1 -     1 -     2    32.0  47.0
           17.5       1 -     1 -     2    32.5  47.5