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In 1610 [[Galileo]] used the newly invented [[telescope]] to observe [[Jupiter]] and discovered four smaller bodies revolving around it.  

In 1610 [[Galileo]] used the newly invented [[telescope]] to observe [[Jupiter]] and discovered four smaller bodies revolving around it.  

Ron Baalke wrote:

[[NASA]] scientist Ron Baalke wrote

* 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]

{{cquote| 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]}}

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.

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.