Merge pull request #3839 from dannygoldstein/sigma_T

added thomson scattering cross section to si units
astropy · Jun 11, 2015 · a5ce6bc · a5ce6bc
2 parents ef4888b + a7658ee
commit a5ce6bc
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diff --git a/CHANGES.rst b/CHANGES.rst
@@ -12,6 +12,8 @@ New Features
 
 - ``astropy.constants``
 
+  - Added the Thomson scattering cross-section. [#3839]
+
 - ``astropy.convolution``
 
 - ``astropy.coordinates``

diff --git a/astropy/constants/si.py b/astropy/constants/si.py
@@ -96,6 +96,10 @@
 mu0 = Constant('mu0', "Magnetic constant", 4.0e-7 * np.pi, 'N/A2', 0.0,
                'CODATA 2010', system='si')
 
+# Thomson scattering cross-section
+sigma_T = Constant('sigma_T', "Thomson scattering cross-section", 0.6652458734e-28, 'm2',
+                   0.0000000013e-28, 'CODATA 2010', system='si')
+
 # DISTANCE
 
 # Astronomical Unit