Galileo's observation of sunspots. Illustration of sunspots as observed by Italian astronomer Galileo Galilei (1564-1642) on 9 June 1612. Galileo was one of the first people to observe sunspots, recording his observations over several months in 1612. He used his telescope, one of the best available at the time, to observe them indirectly and at sunset and sunrise. He published his observations in 'Istoria e Dimostrazioni Intorno Alle Macchie Solari e Loro Accidenti' (1613, History and Demonstrations Concerning Sunspots and their Properties). Sunspots are areas of magnetic activity that are cooler than the rest of the Sun's surface.