Ancient people could see and track the planets closest to Earth — Mercury, Venus, Mars, Jupiter and Saturn. These planets can be seen in the night sky without a telescope. Some speculated that other planets could exist as well, but there was no evidence of this until William Herschel found Uranus.
Once Herschel’s discovery of Uranus was confirmed, it opened up exciting possibilities. With the right tools and expertise in astronomy, people could discover new objects in the solar system.
As telescopes improve, we are able to find smaller objects at greater distances. As our knowledge of the solar system increases, our views about its structure also change.