Caption: "This is an image of a draft written by Galileo (1564--1642) in 1609 August to Leonardo Donato (1536--1612, reigned 1606--1612), Doge of Venice." (Slightly edited.)

It was astonishing just to find 4 new astro bodies. No permanent new ones had ever been found in recorded history: comets and new stars (now identified as novae and supernovae) had come and gone.

Credit/Permission: Galileo Galilei (1564--1642) 1609 (uploaded to Wikimedia Commons by User:Ergzay, 2013) / Public domain.
Image link: Wikimedia Commons.
Local file: local link: galilean_moons_galileo_alternate.html.
File: Galileo file: galilean_moons_galileo_alternate.html.