Using SI units in astronomy

Cover......Page 1
USING SI UNITS IN ASTRONOMY......Page 2
Title......Page 4
Copyright......Page 5
Contents......Page 6
Preface......Page 10
Acknowledgements......Page 13
1.1 Using SI units in astronomy......Page 16
1.2 Layout and structure of the book......Page 17
1.3 Definitions of terms (lexicological, mathematical and statistical)......Page 18
1.3.1 Lexicological and mathematical......Page 19
1.3.2 Statistical......Page 21
1.4 A brief history of the standardization of units in general......Page 22
1.5 A brief history of the standardization of scientific units......Page 23
1.7.2 Recommendations......Page 26
2.2 The set of SI derived units......Page 27
2.3 Non-SI units currently accepted for use with SI units......Page 28
2.5 Prefixes to SI units......Page 29
2.5.3 Powers of 1000......Page 32
2.5.4 Some astronomical examples......Page 34
2.6 IAU recommendations regarding SI units......Page 35
2.6.3 Distance and mass......Page 37
2.7.2 Recommendations......Page 38
3.1.2 Dimensions of some of the SI derived units......Page 39
3.2 Dimensional equations......Page 40
3.3.2 Recommendations......Page 44
4.2.1 Converting from (° \' \"
) and (h m s) to radians......Page 45
4.3.2 Coordinate systems in astronomy......Page 51
4.3.3 Relationships between astronomical coordinate systems......Page 58
4.4.1 Distances between pairs of astronomical objects......Page 61
4.4.2 Field or plate scale determination......Page 62
4.5.1 Conversions between sexagesimal and steradian measures......Page 63
4.5.3 Further examples of angular area measurement in astronomy......Page 64
4.6.2 Recommendations......Page 68
5.3 Systems of time or time scales......Page 69
5.3.3 Time systems currently in use......Page 70
5.3.5 Leap second......Page 72
5.3.9 ISO8601 standard on dates and time......Page 73
5.5.2 Rotation period and period of revolution......Page 75
5.5.3 Proper motions......Page 76
5.5.4 Proper-motion catalogues......Page 78
5.6.1 Nucleocosmochronology......Page 81
5.6.2 Pulsars......Page 83
5.7.1 Summary......Page 85
5.7.2 Recommendations......Page 86
6.2.1 Size of the Earth......Page 87
6.2.2 Distance to the Moon......Page 89
6.2.3 Astronomical unit......Page 90
6.2.4 Solar parallax......Page 92
6.2.5 Horizontal parallax via gravitational microlensing......Page 93
6.2.6 Trigonometric parallax......Page 94
6.2.7 Parsec......Page 95
6.2.9 Some examples of astronomical distances......Page 97
6.3 Linear motion......Page 98
6.3.1 The speed of electromagnetic radiation......Page 99
6.3.3 Space motion of stars......Page 100
6.3.4 Red shifts and look-back times......Page 102
6.4 Acceleration......Page 103
6.6 Volume......Page 104
6.7.2 Recommendations......Page 106
7.1.2 The stability of the International Prototype Kilogram......Page 107
7.1.3 Possible future definitions of the kilogram......Page 108
7.2 The constant of gravitation......Page 109
7.2.1 Values of G measured in some other systems of units......Page 110
7.2.2 Standard gravitational parameter......Page 111
7.3.1 The solar mass......Page 112
7.3.2 Mass of the Earth......Page 114
7.3.3 Masses of Solar System objects......Page 115
7.3.4 Stellar masses......Page 117
7.3.5 Mass loss and gain......Page 120
7.4 Density......Page 121
7.5.1 Energy......Page 123
7.6 Moments of inertia and angular momentum......Page 124
7.7.2 Recommendations......Page 126
8.2 Radiometry and photometry......Page 128
8.2.1 Common astronomical photometric units......Page 131
8.2.2 Wavelengths to frequencies......Page 132
8.2.3 The conversion of some commonly used photometric systems from wavelength to frequency space......Page 133
8.2.4 Determination of the spectral irradiance and the monochromatic flux density of stars from a selection of published values in non-SI units......Page 139
8.2.5 Low-frequency, high-frequency and wavenumber unit conversions......Page 144
8.3 Magnitudes......Page 152
8.3.1 A proposed magnitude system based on radiometric measures......Page 153
8.4.1 Summary......Page 157
8.4.2 Recommendations......Page 159
9.1.3 Thermodynamic temperature......Page 161
9.2 Temperature scales......Page 162
9.2.1 Converting the Celsius, Fahrenheit and Rankine scales to the Kelvin temperature scale......Page 163
9.3 Some examples of the temperatures of astronomical objects......Page 164
9.4 Blackbody radiation......Page 166
9.4.2 Stefan–Boltzmann law......Page 168
9.5.1 Energy states in atoms......Page 169
9.5.2 Energy levels for the hydrogen atom......Page 171
9.5.3 The Saha–Boltzmann equation......Page 174
9.5.4 Equivalent width of a spectral line......Page 175
9.5.5 Colour temperature......Page 176
9.5.6 A lookup table to convert (B−V) colour index to effective temperature......Page 178
9.6.1 Kurucz model stellar atmospheres......Page 180
9.6.2 Conversion of Kurucz model output from cgs to SI units......Page 181
9.6.3 Mean monochromatic flux densities from Kurucz models......Page 182
9.6.4 Selection of best fitting model......Page 186
9.7.1 Summary......Page 187
9.7.2 Recommendations......Page 188
10.1.2 Definition of electricity......Page 189
10.2 SI and non-SI electrical and magnetic unit relationships......Page 190
10.2.1 A comparison between some electric and magnetic mathematical relationships in the SI and cgs Gaussian system......Page 193
10.2.2 Converting unrationalized cgs Gaussian units to SI units......Page 194
10.3 Magnetic fields in astronomy......Page 198
10.3.1 Measurement of astronomical magnetic fields......Page 201
10.3.2 Magnetic fields of Solar System objects and interplanetary space from spaceborne magnetometers......Page 205
10.3.3 Faraday rotation......Page 206
10.4.2 Measured electric fields, potentials and currents in, around, near and on astronomical bodies......Page 209
10.5.2 Recommendations......Page 210
11.2.1 Atomic and molar masses......Page 212
11.2.2 Average atomic mass......Page 213
11.2.3 Molecular mass......Page 214
11.2.4 Mass spectrometer......Page 215
11.2.5 Some further constants involving the mole......Page 216
11.3 Astrochemistry and cosmochemistry......Page 217
11.3.1 Interstellar chemistry......Page 218
11.4.1 Summary......Page 219
12.2 Classification in astronomy......Page 221
12.3 Classification of stellar objects......Page 222
12.3.1 Stellar identity......Page 223
12.3.2 Classification by brightness......Page 224
12.3.3 Spectral classification of stars......Page 225
12.3.4 Classification of star clusters......Page 227
12.3.5 Morphological classification of galaxies......Page 228
12.4.2 Definition of a dwarf planet in the Solar System......Page 230
12.5.1 Astronomical databases......Page 231
12.5.2 Virtual observatories......Page 232
12.6.2 Recommendations......Page 233
References......Page 234
Index......Page 241