Satellite Reports Data About Stars
After 11 months in orbit, a satellite telescope designed here has mapped 7 per cent of the sky and is still sending back new information on ultra-violet light from distant stars. Analysis of data already received from the satellite has yielded several results.
Robert J. Davis '51, associate of the Harvard College Observatory and director and designer of the orbiting telescope called Project Celescope, said he has reached two important conclusions from the data analyzed so far. He discovered that "Diffuse nebulae-large interstellar hydrogen gas clouds in which stars are formed-are brighter than we can easily explain."
He also observed that "blue giants-massive, hot stars-are fainter in the ultraviolet than the rest of the main sequence stars" (Main sequence stars are middle-aged stars such as the sun). This second result can be explained by the structure of the blue giants. Davis said, but the reason for the brightness of
hydrogen gas clouds is still unknown.
So far the telescope cameras have sent back nearly 5000 ultraviolet pictures, primarily photographing the stars lying in the plane of the Milky Way. A satellite was necessary to obtain these pictures because the earth's atmosphere blocks most types of ultra-violet light and makes ground observations in ultra-violet wave-lengths impossible.
The satellite's cameras have photographed star clusters, especially the Orion and Pleides star associations. Ultra-violet pictures were taken of the moon, but they showed nothing surprising, Davis said.
"Failures in the satellite are occurring as predicted, 'Davis said. "Of the four telescope cameras, three are still operating and two are producing reliable data," he added. Before Project Celescope was launched from Cape Kennedy, scientists gave it a 70 per cent chance of lasting one year. The current condition of the cameras indicates that the telescope will operate for at least part of a second year.
Project Celescope is somewhat limited because it "can only operate over a ground station," Davis said.
The satellite makes fifteen to twenty ground station contacts each day, Davis added, and it sends as many as 18 pictures in a single transmission. The five stations now used by Project Celescope are located in North Carolina, Madagascar, Chile, Ecuador, and Australia.
"About 30 per cent of the data analysis task has been completed," Davis said, but the complete analysis will take several years.