The Essential Galileo (13 page)

There was an interval of five minutes from the star on the east to Jupiter, [85] and from Jupiter to the star furthest to the west seven minutes. The two interior stars on the western side were forty seconds apart, and the star nearer to Jupiter was one minute from the planet. The inner stars were smaller than the outer ones, but they were situated all in the same straight line, along the zodiac, except that the middle of the three western stars was slightly to the south of it. However, at the sixth hour of the night, they appeared in this position:

The star on the east was very small, at a distance from Jupiter of five minutes, as before. But the three stars on the west were separated by equal distances from Jupiter and from each other; and the intervals were nearly one minute and twenty seconds each. The star nearest Jupiter appeared smaller than the other two on the same side, but they all appeared arranged exactly in the same straight line.

On 23 January at forty minutes after sunset, the configuration of the stars was nearly after this fashion:

There were three stars with Jupiter in a straight line along the zodiac, as they have always been. Two were on the east of the planet, one on the west. The star furthest to the east was seven minutes from the next one; this star was two minutes forty seconds from Jupiter; and the star on the west was three minutes twenty seconds from Jupiter. They were all of nearly the same size. But at the fifth hour the two stars that had been previously near Jupiter were no longer visible, being, I suppose, hidden behind Jupiter; and the appearance was this:

On 24 January three stars, all on the east side, were visible and almost, but not quite, in the same straight line with Jupiter, for the star in the middle was slightly to the south of it:

The star nearest to Jupiter was two minutes from it; the next was thirty seconds from that star; and the third was nine minutes further still. They were all very bright. But at the sixth hour only two stars presented themselves, in this position:

namely, in the same straight line with Jupiter exactly. [86] The distance of the nearest to it had lengthened to three minutes, and the next was eight minutes further off. Unless I am mistaken, the two stars previously observed in the middle had come together and appeared as one.

On 25 January at one hour and forty minutes, the stars were grouped thus:

There were only two stars on the east side, and they were rather large. The star furthest to the east was 5 minutes from the star in the middle, and it was six minutes from Jupiter.

On 26 January at forty minutes, the relative positions of the stars were thus:

Three stars were in view, of which two were east and the third west of Jupiter. This third star was three minutes from the planet; on the east side, the star in the middle was at a distance of five minutes and twenty seconds, and the further star was six minutes beyond. They were arranged in a straight line and were of the same size. At the fifth hour the arrangement was nearly the same, with this difference only, that the fourth star was emerging on the east side near Jupiter. It was smaller than the rest and was then at a distance of thirty seconds from Jupiter; but it was raised a little above the straight line towards the north, as the following figure shows:

On 27 January at one hour after sunset, a single star was in view, on the east side of Jupiter, in this position:

It was very small and at a distance of seven minutes from Jupiter.

On 28 and 29 January, owing to the interference of clouds, I could make no observation.

On 30 January at the first hour of the night, the stars were in view, arranged in the following way:

There was one star on the east side, at a distance of two minutes and thirty seconds from Jupiter; and there were two stars on the west, of which the one nearer to Jupiter was three minutes off the planet, and the other star one minute further. The outer stars and Jupiter were in the same straight line; but the star in the middle was a little above it to the north. The star furthest to the west was smaller than the rest.

[87] On the last day of the month, at the second hour, two stars on the east side were visible, and one on the west: