From The Galileo Project website’s page on Galileo’s drawings of sunspots:
In 1612 during the summer months, Galileo made a series of sunspot observations which were published in Istoria e Dimostrazioni Intorno Alle Macchie Solari e Loro Accidenti Rome (History and Demonstrations Concerning Sunspots and their Properties, published 1613). Because these observations were made at appoximately the same time of day, the motion of the spots across the Sun can easily be seen.
Our Solar System and the Pluto Problem
From lecture 3 in professor Charles Bailyn’s ASTR 160: Frontiers and Controversies in Astrophysics:
Bailyn first reminds us of the scientific method and that astronomy is an observational science. He then talks about classification and the six categories of objects in the Solar System:
Sun (a star). Inner, sometimes called terrestial or rocky, planets. Asteroids. Outer, also known as Jovian, planets. Trans-Neptunian, or Kuiper Belt, objects. _Comets in the outer region, or Oort cloud.