Radiation
laws � apply to astronomical sources
Wien�s law :
�������� lpeak = 0.289 / T(K) cm�
lpeak � color: hotter � bluer (shorter l)
���������������������� cooler � redder (longer l)
�Greater total energy (summed over
all wavelengths) radiated by hotter objects�������������
����������������������������� �
Stefan�s Law :
energy radiated/unit area
of B-B surface/unit time � (temp)4
���������������������� F = sT4
� Flux� = 5.67x 10-8T4�watt/m2/K4
�Stefan�s constant = s
For T = 6000 K, lpeak=4800�
radiation appears
yellow
For T = 3000 K, lpeak=9700�
�near infrared
If T x2, Fx24� 16xpower