What did Galileo Galilei observe with a telescope in 1610?

In 1610, Galileo Galilei made several groundbreaking astronomical observations using his improved telescope, which fundamentally challenged the prevailing Aristotelian view of the universe.12

His key discoveries in 1610 included:

• The Moons of Jupiter: In January 1610, he discovered four satellites revolving around Jupiter, which provided evidence that celestial bodies could orbit something other than Earth.12
• The Stars: He observed that the telescope revealed a vast number of stars invisible to the naked eye.1
• The Phases of Venus: He discovered that Venus exhibits phases similar to those of the Moon, indicating that it orbits the Sun.12

Additionally, while his observations of the Moon's rough, mountainous surface and the appearance of Saturn occurred around this same period, these findings collectively helped dismantle the belief in a perfect, unchanging heaven and supported the heliocentric system proposed by Nicolaus Copernicus.12