After the invention of the telescope, astronomy changed. Astronomers could see many more objects in the night sky.
Telescopes also made it possible to study planets and moons in much greater detail.
Early astronomers knew of five planets beyond Earth: Mercury, Venus, Mars, Jupiter, and Saturn. These are the five planets visible to the naked eye.
You can read more below.
Timeline: How telescopes changed our view of the Solar System
- Before telescopes
Five planets known using the naked eye - 1655
Saturn’s rings and its moon Titan discovered - 1680
Halley observes a comet and predicts its return - 1781
Uranus discovered using a telescope - 1845
Neptune predicted using maths and then observed - 1801 → today
Asteroids discovered and the asteroid belt identified - 1930 → 2006
Pluto discovered, then reclassified as a dwarf planet
In 1655, Christiaan Huygens used a telescope he built himself to study Saturn. He discovered Saturn's rings and its largest moon, Titan.
In 1680, Edmund Halley observed a comet moving across the sky. He calculated the comet’s orbit and predicted its return. He was correct, and the object is now called Halley’s Comet.
In 1781, William Herschel discovered Uranus using a telescope he built himself. This was the first new planet found in thousands of years.
In 1801, the first asteroid, Ceres, was discovered. Soon after, Pallas was found. Astronomers now know that more than 100,000 asteroids orbit the Sun between Mars and Jupiter in a region called the asteroid belt.
In 1845, Neptune was discovered by British and French astronomers. They used mathematics to predict the position of another planet. Neptune was found at the predicted location.
From 1930 to 2006, nine planets were recognised in the Solar System. Then, in 2005, Eris and other objects were discovered. A new category called dwarf planets was created. In 2006, Pluto and Ceres were reclassified as dwarf planets.