| − | In June or July of 1609, five years after his initial discovery, Galileo heard about the telescope, which had been invented in [[Netherlands|Holland]]. Without knowing the technical details of the construction of the device, he was able to create one for himself. Over time he continued to upgrade it. He found mountains on the Moon, viewed the phases of [[Venus]], and discovered four satellites around [[Jupiter]] as well as locating [[sunspots]]. He published his finding in a paper titled "The stary messenger" which he dedicated to Grand Duke Cosimo II. His discoveries and publication led him to be appointed as Grand Duke court mathematician, a position he had coveted. | + | In June or July of 1609, five years after his initial discovery, Galileo heard about the telescope, which had been invented in [[Netherlands|Holland]]. Without knowing the technical details of the construction of the device, he was able to create one for himself. Over time he continued to upgrade it. He found mountains on the Moon, viewed the phases of [[Venus]], and discovered four satellites around [[Jupiter]] as well as locating [[sunspots]]. |
| | + | * Galileo first observed the moons of Jupiter on January 7, 1610 through a homemade telescope. He originally thought he saw three stars near Jupiter, strung out in a line through the planet. The next evening, these stars seemed to have moved the wrong way, which caught his attention. Galileo continued to observe the stars and Jupiter for the next week. On January 13, a fourth star appeared. After a few weeks, Galileo had observed that the four stars never left the vicinity of Jupiter and appeared to be carried along with the planet, and that they changed their position with respect to each other and Jupiter. Finally, Galileo determined that what he was observing were not stars, but planetary bodies that were in orbit around Jupiter. [http://www2.jpl.nasa.gov/galileo/ganymede/discovery.html] |