Jan Oort.
See <a href="//commons.wikimedia.org/wiki/File:JanOort.jpg" title="File:JanOort.jpg">File:JanOort.jpg</a> for original file. <a href="//commons.wikimedia.org/wiki/User:SenseiAC" title="User:SenseiAC">SenseiAC</a> for cropping the original file into this file.
Derived from <a href="//commons.wikimedia.org/wiki/File:JanOort.jpg" title="File:JanOort.jpg">File:JanOort.jpg</a>.