"Spectroscopic examination. That collector field of ours gathers energy just like a burning glass. You've seen a burning glass, haven't you?"
He stared at Stutsman, directing the question at him. Stutsman shuffled awkwardly, unhappily.
"Well,” Craven went on, “I used that for a telescope. Gathered the light from the suns and analyzed it. Of course it didn't act like a real telescope, produce an image or anything like that, but it was ideal for spectroscopic work."
They waited for him to explain. Finally, he continued:
"All of the stars I examined were just type G stars, nothing else but there was a difference in one of them. First, the spectroscope showed lines of reflected light passing through oxygen and hydrogen, water vapor and carbon dioxide. Pure planetary phenomena, never found on a star itself. Also it showed that a certain per cent of the light was polarized. Now remember that I examined it for a long time and I found out something else from the length of observation which convinces me. The light varied with a periodic irregularity. The chronometers aren't working exactly right out here, so I can't give you any explanation in terms of hours. But I find a number of regularly recurring changes in light intensity and character… and that proves the presence of a number of planetary bodies circling the star. That's the only way one could explain the fluctuations for the G-type star is a steady type. It doesn't vary greatly and has no light fluctuations to speak of. Not like the Cephids and Mira types."
"And that proves it's our Sun?” asked Chambers.
Craven nodded. “Fairly definitely, I'd say."
"How far away is it?” Stutsman wanted to know.
Craven snorted. “You would ask something like that."
"But,” declared Stutsman, “there are ways of measuring how far a star is away from any point, measuring both the distance and the size of the star."