astro.py 文件源码

def arcsec2pc(d=15.,a=1.):
    """
Given the input angular size and distance to the object, computes
the corresponding linear size in pc. 

:param d: distance in Mpc
:param a: angular size in arcsec
:returns: linear size in pc
    """

    # convert arcsec to radians
    a=a*4.848e-6    
    # convert distance to pc instead of Mpc
    d=d*1e6

    return d*numpy.tan(a)