The Essential Galileo (12 page)

They were, that is to say, in the same straight line to a hair. The nearest to Jupiter was very small and distant from the planet three minutes; the distance of the second from this one was one minute; and of the third from the second four minutes and thirty seconds. But after another hour the two middle stars were still nearer, for they were only thirty seconds, or less, apart.

[83] On 16 January at the first hour of the night, I saw three stars arranged in this order:

Jupiter was between two of them that were at a distance of forty seconds from the planet on either side, and the third was west of Jupiter at a distance of eight minutes. The stars near to Jupiter appeared brighter than the star further off, but not larger.

On 17 January at thirty minutes after sunset, the configuration was of this kind:

There was only one star to the east, at a distance of three minutes from Jupiter; to the west likewise there was only one star, distant eleven minutes from Jupiter. The star on the east appeared twice as large as the star to the west; and there were no more than these two. But four hours later, that is, at almost the fifth hour, a third star began to emerge on the east side, which I think before its appearance had been joined with the former of the two other stars. The position was this:

The middle star was very near indeed to the star on the east, namely only twenty seconds from it; and it was a little towards the south of the straight line drawn through the two outermost stars and Jupiter.

On 18 January at twenty minutes after sunset, the appearance was such as this:

The star to the east was larger than the western one, and it was at a distance from Jupiter of eight minutes, the western one being at a distance of ten minutes.

On 19 January at the second hour of the night, the relative position of the stars was such as this:

That is, there were three stars exactly in a straight line with Jupiter, one to the east at a distance of six minutes from Jupiter. Between Jupiter and the first star to the west, there was an interval of five minutes. This star was four minutes off the other one more to the west. At that time I was doubtful whether or not there was a star between the star to the east and Jupiter, but so very close to Jupiter as almost to touch the planet. But at the fifth hour I saw this star distinctly, [84] by that time occupying exactly the middle position between Jupiter and the eastern star, so that the configuration was thus:

Moreover, the star that had just come into view was very small. But at the sixth hour it was nearly as large as the rest.

On 20 January at one hour and fifteen minutes, the arrangement was like this:

There were three stars, so small as scarcely to be visible. Their distances from Jupiter, and from one another, were not more than one minute. I was doubtful whether on the western side there were two stars or three. At about the sixth hour, they were grouped in this way:

The eastern star was twice as far away from Jupiter as before, that is two minutes. On the western side, the star in the middle was distant from Jupiter forty seconds, and from the star still further to the west twenty seconds. Finally, at the seventh hour, three stars were seen on the western side:

The star nearest to Jupiter was distant from the planet twenty seconds. Between this one and the star furthest to the west there was an interval of forty seconds. But between these another star was in view slightly southward of them, and not more than ten seconds off the most westerly star.

On 21 January at thirty minutes, there were three stars on the east side; they and Jupiter were at equal distances apart:

The intervals were estimated to be fifty seconds each. There was also one star on the west, distant four minutes from Jupiter. The star on the east side nearest to Jupiter was the smallest of all.

On January 22 at the second hour, the arrangement of the stars was this: