THE SOUTHWORTH PLANETARIUM
207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N                   70.2667° W
Founded January 1970
                "Another one airborne."




*THE DAILY ASTRONOMER*
*Monday, July 25, 2016*
*Galileo's Ego *


----------------------------------------------------------------------------------------
CHRISTMAS IN JULY!
On Monday, July 25, 2016 we're opening a secret space-time conduit from
this gloriously hot summer into the festive winter season.   Today only,
you can see our annual holiday show "Season of Light."  Narrated by NPR's
Noah Adams, this show examines the historical and astronomical aspects of
the holiday season.  What is the origin of Santa Claus, the solstice
festivals, Hannukkah, New Year's Eve and the other traditions.

Showings at 11:00 a.m. and 1:00 p.m. today.
Admission    $5.50 - adults;  $5.00 - children, seniors
For more information, call 207-780-4249 or consult our web-site
www.usm.maine.edu/planet

Note: After today, the next public showing of "Season of Light" is
scheduled for November 26
----------------------------------------------------------------------------------------


Well, we won't empty Pandora's Jar before the school year ends on August
2.   Honestly, we didn't expect to do so.   We're receiving more questions
that we're answering, presently.  We'll step up our pace a bit  but,
happily, we'll never catch up.      Today, we address a question that is
more historical than astronomical.


*"The Galilean Moons were named for Galileo, who discovered them.  Did he
name them after himself?  If so, what an ego!"*            -Anonymous,
Portland

Greetings!
Well, some scientific historians have claimed that Galileo did think well
of himself.  After all, he *was *Galileo Galilei.     However, he wasn't so
self-serving as to have named Jupiter's four largest moons after
himself.    That happened well after their discovery.   Now, we'll review
some history.    Galileo was said to have discovered Jupiter's four largest
satellites in 1609 or early 1610, soon after he made modifications to the
telescope.*   These moons are, in order going away from Jupiter, Io,
Europa, Ganymede and Callisto.


*A copy of  a page from Galileo's "Sidereus Nuncius,' ("The Starry
Messenger") 1610.  Here we see Jupiter depicted as a large circle with
smaller "stars" at either side of that represent the "Galilean Moons,"
Io, Europa, Ganymede and Callisto.   Each image shows Jupiter on different
nights.   We see how the configuration of these moons varies over time,
thereby indicating orbital motion around Jupiter.  *
*Image:  History of Science Collections, University of Oklahoma Libraries*


He first recorded the discovery of these moons in his book "Sidereus
Nuncius," (The Starry Messenger.)  He named these Jovan satellites "Cosmica
Sidera," after his patron Cosimo II de' Medici, the Duke of Tuscany.
Galileo had served as Medici's tutor when the latter was a child and in
adulthood Medici was one of Galileo's most loyal patrons and supporters.
Naming the moons for his patron was a grand gesture of gratitude or,
perhaps, a calculated means of assuring that the patronage would
continue.   Some claim that the Duke, himself, suggested the name and the
politically astute Galileo readily agreed.


​*The "Galilean Moons"  (L-R)  Io, Europa, Ganymede and Callisto.  Although
Galileo is credited with their discovery, he did not assign them these
mythological names.   Image: Pearson Education, Inc.*

Interestingly -well, it's interesting to us- the actual names of the
individual moons, -Io, Europa, Ganymede and Callisto- were coined by German
Astronomer Simon Marius (1573-1624).   Marius claimed to have discovered
the same moons five weeks prior to Galileo's first observation of them.
However, as Marius did not publish his results, Galileo received the credit
for their discovery.     At Johannes Kepler's suggestion. Marius did name
the moons after some of Zeus' lovers.  Galileo refused to confer these
mythological names onto the moons, opting instead to assign them the Roman
numerals I, II, III, and IV, a convention that some astronomical charts
still use today.



*Galileo Galilei did not invent the telescope.    German-Dutch lens maker
Hans Lippershey (1570-1619) is credited with having invented the telescope,
but even this claim is uncertain.  While in Venice, Galileo learned of this
new invention, then called the "Dutch Perspective Glass," capable of
enlarging distant objects to allow for closer scrutiny.   He returned to
Padua and constructed his own device with certain modifications.  He
devoted a year to perfecting the telescope and enhancing its
capabilities.  He eventually built a telescope capable of magnifying an
image