Tuesday, January 7, 2014

Galileo spies 3 new stars near Jupiter

Looking through his newly improved spyglass, Galileo observes 3 new stars previously unseen near Jupiter. Here is his observation from January 7, 1610:

"Accordingly, on the seventh day of January of the present year 1610, at the first hour of the night, when I inspected the celestial constellations through a spyglass, Jupiter presented himself. And since I had prepared for myself a superlative instrument, I saw (which earlier had not happened because of the weakness of the other instruments) that three little stars were positioned near him, small but yet very bright. Although I believed them to be among the number of fixed stars, they nevertheless intrigued me because they appeared to be arranged exactly along a straight line and parallel to the ecliptic, and to be brighter than others of equal size. And their disposition among themselves and with respect to Jupiter was as follows:"
Observation by Galileo
January 7, 1610
Below is a simulation of what Jupiter looked like on the night of Jan 7, 1610 using Sky & Telescope's "Jupiter Moons" app.
Courtesy of Sky & Telescope

Of course we now know those little stars are in fact 3 of Jupiter's 4 major moons. Below is a photo I took last December of Jupiter in a somewhat similar configuration.

Jupiter Observation by Me
December 11, 2013