Presence of 6707 A. Radiation in the Twilight Sky

Abstract

SINCE August 5, 1958, a patrol spectrograph at Hallett Station in Antarctica has frequently shown the presence of a strong emission line in the region of 6705 A. from the twilight sky. Following a report of this, a grating spectrograph at Invercargill, New Zealand, was exposed on September 5, 1958, to the radiation coming from the twilight sky between the horizon and 20° altitude, on a bearing of 175° (true). A feeble line at 6707 ± 2 A. was detected on this occasion, and on several subsequent occasions. The use of a minus ultra-violet filter confirmed that the line was in the first-order spectrum. Exposures at varying states of twilight showed that the line was enhanced in twilight at about the same time as the well-known sodium D-line enhancement. Hallett station has also observed this twilight enhancement, both morning and evening, from the date of the first detection.