View Full Version : The Medicean planets

2003-Dec-27, 08:31 PM
The Medicean planets

After conducting star counts in the Great Nebulae of Orion and in Praesepe (The Beehive Cluster in Cancer - The Crab), Galileo then noticed that the planet of Jupiter was now easily visible.

On the night of January 7, 1610, Galileo wrote the following concerning his observation of the giant planet, "I perceived that besides the planet there were three starlets, small indeed, but very bright. Though I believe them to be among the host of fixed stars, they aroused my curiosity somewhat by appearing to lie in an exact straight line parallel to the ecliptic, and by their being more splendid than others of their size."

Galileo's detailed sketch showed that one 'starlet' had appeared just west of Jupiter while two other 'starlets' appeared to the east.

The next night, Galileo noticed that these 'starlets' were no longer where they should be! Now, these three small, bright objects were all on the western side of Jupiter! And, to him, it looked like Jupiter was moving easterly in relation to the background of fixed stars.

At first, the bearded and graying astronomer thought the computations made by other astronomers were wrong because Jupiter was in retrograde motion and appeared to be traveling west among the stars. This aroused his curiosity and Galileo eagerly waited for the next night.

When the next evening arrived, the weather was not favorable for observing Jupiter and Galileo was forced to wait for another clear night.

On the night of January 10th, Galileo turned his small telescope upon the planet Jupiter and received another surprise! The 'starlets' that Galileo had observed had moved again! This time, only two 'starlets' were visible and they were both on the eastern side of the planet! As for the third 'starlet,' Galileo theorized that this particular 'starlet' was now hiding behind Jupiter.

Puzzled and perplexed, Galileo was now certain, that Jupiter was not the cause of these motions, but that these three stars must be. His curiosity quickly turned into amazement!

When night fell on January 11th, Mother Nature once again tricked Galileo! Peering through his telescope, Galileo saw that while there were still two 'starlets' on the eastern side of Jupiter one of those 'starlets', (which had been the closest to Jupiter) is now three times further away! Plus, the farthest 'starlet' is now double the size as it was the night before!

The cold wind chilled Galileo as he again wrapped his cloak around his aging body. And, Galileo softly muttered under his breath, "How could this be? Yesterday, both 'starlets' were of the same size."

After much thought, Galileo concluded, that without a doubt these three 'stars' wandered around Jupiter in the same manner as Mercury and Venus does around the sun.

Right after sunset, on January 12th, Galileo saw only two bright 'starlets' each one flanking Jupiter, but the 'starlet' on the eastern side appeared slightly larger. And, because Galileo now realized that these 'starlets' quickly changed their positions, he decided to keep checking their positions every hour.

Two hours passed by. Then Galileo observed, that a third 'starlet' was beginning to appear on the eastern side or limb of Jupiter. And, this little 'starlet' not only appeared to be touching the giant planet, but was also rather small in size.

Still amazed, but with curiosity burning brightly, Galileo observed a fourth 'starlet' on the evening of January 12th! But this time three 'starlets' were on the western limb of Jupiter while a fourth was on the eastern limb! Galileo also noticed that the group formed a straight line except that the middle and western most 'starlet' was slightly towards the north. In addition, the eastern 'starlet' was two minutes of arc away from Jupiter while the other three 'starlets' were separated by one arc minute from each another.

It seems that once again the weather or something worse decided to give him a break because his notes do not start back up until the twenty-sixth of February. Looking threw what notes I can find; I have yet to find any entries for that time frame. I think it would be rather odd for someone to find so excited a discovery to just throw it on the back burner

He went on to write “But now we have not just one planet rotating around about another while both run through a great orbit around the sun; our own eyes show us four stars which wander around Jupiter as does the moon around the Earth, while all together trace out a grand revolution about the Sun in the space of twelve years “

Finally, as was the custom in those days, Galileo named his group of 'starlets' the Medicean planets in honor of the wealthy and well-known Medici family residing in Italy. Today, we now know this little group of four moons (Io, Europa, Callisto, and Ganymede) as the Galilean satellites, which were named in honor of Galileo.

2003-Dec-27, 08:55 PM
:lol: :lol: :lol: :lol: :lol: Here's more :lol: :lol: :lol: :lol:
http://web.clas.ufl.edu/users/rhatch/pages...p-b-planet6.htm (http://web.clas.ufl.edu/users/rhatch/pages/03-Sci-Rev/SCI-REV-Home/resource-ref-read/chief-systems/boulliau-prob/06rp-b-planet6.htm)

2003-Dec-27, 11:38 PM
The Medici family resided in Florence. Italy as we know it did not exist until modern times.

2004-Jan-01, 05:33 AM
I remember when I was in, I think it was second grade, I found this book in the school library about Galileo and Jupiter's moons, and for the whole year I would check it out, renew it, return it, check it out again. Mostly I just looked at the pictures and read the captions, but I did read some of the text. I loved that book, and Galileo was a big influence and inspiration for me. So I remember reading about all that stuff you mentioned, even though it was quite a few years ago. I should try to find that book again. I think it was called "The Moons of Jupiter."