Number of Planets: Answering this question may seem straightforward, but it carries some complexity...

In the late 1980s and early 1990s, astronomers began to uncover a new frontier in our Solar System. They discovered large objects lurking beyond Neptune, known as Trans-Neptunian Objects (TNOs). These icy bodies, including Eris, a large object discovered in 2005, populate the Kuiper Belt, a region on the edge of our Solar System.

The Solar System, as we once knew it, consisted of nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. However, Pluto's status as a planet has been a topic of debate since 2006, when it was reclassified as a 'dwarf planet' because it did not meet the third criterion for planethood. According to the International Astronomy Union, a planet must orbit the Sun, be rounded off by gravity, and have enough gravity of its own to clear its orbital path of debris.

The reclassification of Pluto opened up a new discussion about what constitutes a planet. In response, the International Astronomy Union decided in 2006 that a new, stricter definition of the word 'planet' was required. Under this new definition, Eris, with its size comparable to Pluto but with 27% more mass, was also reclassified as a 'dwarf planet'.

Meanwhile, our understanding of the universe has expanded beyond our Solar System. In 1992, astronomers positively identified the first exoplanet, a planet orbiting a star outside our own Solar System. As of 2025, the exact number of confirmed exoplanets in the universe is not precisely known, but astronomers have discovered thousands within our galaxy, and estimates suggest billions of habitable exoplanets in the Milky Way alone. The total number of exoplanets in the entire universe remains undetermined, but it is believed to be vast, with bloomin' gazillions of them.

This discovery has strengthened the argument that Pluto should not be considered a planet in the traditional sense. Many astronomers now believe that wherever you see a star, you'll find at least one planet, if not an entire planetary system akin to our own. And while Earth may still be the happiest of the 8 planets in our Solar System, according to a poll of astronauts and cosmonauts, the potential for life beyond our own planet is more exciting than ever.

Number of Planets: Answering this question may seem straightforward, but it carries some complexity...