Far Probe did it for us.'
Pitt could feel himself igniting, a distant core of warmth arising within him. He said, 'Do you mean that the Far Probe took a picture of that section of the sky containing this Neighbor Star and that the Far Probe was far enough out in space to see around the cloud and detect the Neighbor Star at full brightness?'
'Exactly. We had an eighth-magnitude star where no eighth-magnitude star ought to be, and the spectrum was that of a red dwarf. You can't see red dwarf stars far away, so it had to be pretty close.'
'Yes, but why closer than Alpha Centauri?'
'Naturally, I studied the same area of the sky as seen from Rotor and the eighth-magnitude star wasn't there. However, fairly near it was a nineteenth-magnitude star that wasn't present in the photograph taken by the Far Probe. I assumed that the nineteenth-magnitude star was the eighth-magnitude star, obscured, and the fact that they weren't exactly in the same place had to be the result of parallactic displacement.'
'Yes, I understand about that. A nearby object appears to be in different places against the distant background as one views it from different spots.'
'That's right, but the stars are so distant that even if the Far Probe went out a big fraction of a light-year that change in position wouldn't produce a noticeable shift in distant stars, but it would in nearby stars. And for this Neighbor Star, it produced a huge shift; I mean, comparatively. I checked the sky for different positions of the Far Probe on its journey outward. There were three photographs taken during those intervals when it was in normal space, and the Neighbor Star was progressively brighter as the Probe viewed it farther and farther toward the edge of the cloud. From the parallactic displacement, the Neighbor Star turns out to be at a distance of just over two light-years. It's at half the distance of Alpha Centauri.'
Pitt looked at her thoughtfully and, in the long silence that followed, she grew restless and uncertain.
'Secretary Pitt,' she said, 'do you want to see the data now?'
'No,' he said. 'I'm satisfied with what you've told me. Now I must ask you some questions. It seems to me, if I understand you correctly, that the chance that someone would concentrate on a nineteenth-magnitude star, and try to get its parallax and determine its distance, is negligible.'
'Just about zero.'
'Is there any other way of noticing that an obscure star must be very near to us?'
'It may have a large proper motion - for a star. I mean that if you watch it steadily, its own motion would change its place in the sky in a more or less straight line.'
'Would that be noticed in this case?'
'It might be, but not all stars have a large proper motion, even if they are close to us. They are moving in three dimensions and we see the proper motion only in a two-dimensional projection. I can explain-'
'No, I'm continuing to take your word for it. Has this star got a large proper motion?'
'That would take some time to determine. I do have a few older pictures of that part of the sky and I could detect an appreciable proper motion, That would need more work.'
'But do you think it has the kind of proper motion that would force itself on astronomers, if they just happened by accident to note the star?'
'No, I don't.'
'Then is it possible that we on Rotor are the only ones who know about this Neighbor Star, since we're the only ones who've sent out a Far Probe? This is your field, Dr Insigna. Do you agree that we're the only ones who've sent out a Far Probe?'
'The Far Probe isn't entirely a secret project, Mr Secretary. We've accepted experiments from the other Settlements and discussed that part of it with everyone, even Earth, which isn't too interested in astronomy these days.'
'Yes, they leave it to the Settlements, which is sensible. But have any other Settlements sent out a Far Probe that they have kept secret?'
'I doubt that very much, sir. They would need hyper-assistance for that, and we have kept the technique of hyper-assistance entirely secret. If they had hyper-assistance, we'd know. They'd have to perform experiments in space that would give the fact away.'
'According to the Open Science Agreement, all data obtained by the Far Probe is to be published generally. Does that mean that you have already informed-'
Insigna interrupted indignantly. 'Of course not.