Spectrometer Gathers More Data On Sun

An ultraviolet spectrometer constructed at the Harvard College Observatory has given Harvard astronomers over 4,000 pictures of the sun, revealing new information about its distribution of elements and temperature.

The pictures are the first ever taken of the sun in ultraviolet light from a satellite.

The spectrometer is aboard Orbiting Solar Observatory IV, launched Oct. 18. The instrument's power supply was turned on Oct. 24; it has been taking about 150 pictures a day since.

The instrument builds up a picture by scanning the sun, back and forth and bottom to top, recording the intensity of ultraviolet radiation of a particular wavelength.

The kind of ions present at various levels of the sun's atmosphere depend on the temperature there. Each kind of ion, a chemical elements stripped of one or more electrons, emits a different wavelength of ultraviolet light.

First True Observatory

Leo Goldberg '34, Higgins Professor of Astronomy, who heads the group which constructed the spectrometer, called the instrument "the first true observatory" last night. "Rather than just an experiment which tells the same thing over and over, the program can be changed if we wish," he said.

"The spectrometer performs a variety of tasks and is responsible to commands by radio from the ground," he added.

The Harvard group decides what kind of pictures will be taken daily. Their decision is sent to the Goddard Space Flight Center in Greenbelt, Md., and relayed to the Observatory in Cambridge.

First Complete View

The spectrometer takes pictures in 50 wavelengths of ultraviolet light, each invisible from the earth's surface.

This is the first time astronomers have been able to study the upper atmosphere of the sun over the whole face of the solar disc rather than just at the edge of the disc during an eclipse.