Harold "Doc" Ewen and Edward Purcell with Harvard Antenna, 1956

Seventy years ago, on 25 March 1951, Harold "Doc" Ewen, working with his Harvard thesis advisor Edward Purcell, made the first observation of HI, neutral interstellar hydrogen, predicted but never before detected. Ewen, as his thesis project, used a horn antenna jutting out of the window of the Lyman Lab at Harvard.

In this photo, taken at the dedication of the Harvard 60 foot antenna in 1956, Ewen (left) and Purcell (right) stand under the 60 foot antenna and beside the horn antenna used for the HI detection, which now sits outside the Jansky Lab at the Green Bank Observatory.

For Ewen's account of the detection, see https://www.nrao.edu/archives/static/Ewen/ewen_HI.shtml.

Records of the NRAO

Still Image

ewen_HI_slide33.jpg

1956

H.I. (Doc) Ewen

Photographs Series

Non-NRAO Instrument Unit