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