How many planets are there? This question seems simple, but the answer heavily depends on how you define a “planet”. Do you say eight, nine, or thousands? The answer is both scientifically and culturally interesting, and the discussion about Pluto plays a major role in this. In this blog, we explain how many planets are in our solar system, which objects no longer qualify, and how many worlds have been discovered outside our solar system.
What is a Planet According to Science (Official Definition)
According to the International Astronomical Union (IAU), there are three conditions an object must meet to be considered a planet:
- It orbits a star (like our sun).
- It has enough mass to achieve a round shape through gravity.
- It has cleared its orbital path of other objects.
Based on this definition, our solar system has eight official planets:
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
What about Pluto?
Until 2006, Pluto was considered the ninth planet. It meets the first two conditions but not the third: Pluto shares its orbit with many other objects in the Kuiper Belt: a ring of icy objects at the edge of the solar system. Therefore, Pluto was reclassified as a dwarf planet.
Besides Pluto, there are four other objects officially recognized as dwarf planets:
- Eris
- Haumea
- Makemake
- Ceres (located in the asteroid belt)
Although dwarf planets are no longer official planets, they remain important for our understanding of the solar system’s formation.
How many Planets are there outside our Solar System?
In recent decades, we’ve been looking far beyond our own solar system. Thanks to telescopes like Kepler, TESS, and James Webb, more than 5,000 exoplanets have been discovered so far. These planets orbit other stars in our Milky Way.
Some exoplanets are similar to Earth, others are gas giants like Jupiter, and some fall into categories we don’t have here, like “super-Earths” or “hot Jupiters”.
🔗 Read more about recent discoveries in our blog about the James Webb Space Telescope
How many are there in Total?
Astronomers estimate that our Milky Way alone contains hundreds of billions of planets. Most haven’t been discovered yet, but their existence is inferred through:
Gravitational influences on other celestial bodies, transit photometry (dimming of light when passing in front of a star) and radial velocity measurements
What are Dwarf Planets and Planetoids?
Besides the eight planets and five official dwarf planets, there are thousands of smaller objects, such as planetoids (asteroids) and TNOs (Trans-Neptunian Objects).
Some of these objects are nearly round and might have gained planet status under a more lenient definition. Thus, the discussion about Pluto and the planet definition remains current, especially in educational circles.
What Can You See Yourself with a Telescope?
While you can’t observe all planets with a telescope, you can see quite a few:
- Jupiter and its moons are visible even with a small telescope.
- Saturn shows its rings from 60x magnification.
- Mars is red and recognizable, especially during opposition (opposition is when a planet is closest to Earth)
- Venus shows phases, just like the moon.
- Mercury is difficult, but sometimes visible at sunrise or sunset.
🔗 Want to know more? Check out our guide to planet observation
Pluto is too small and faint to see with amateur equipment unfortunately… so it misses out again.
Conclusion: how many Planets are there?
The question “how many planets are there actually?” has multiple correct answers, depending on your definition:
| Category | Quantity |
|---|---|
| Official planets | 8 |
| Recognized dwarf planets | 5 |
| Confirmed exoplanets | 5.000+ |
| Expected exoplanets | Hundreds of billions(!) |
It’s clear: our understanding of planets is dynamic. As we develop new technologies and look further into the universe, these numbers will continue to grow.
Want to know more about which telescope you need to see planets? Read our beginner’s guide or read here an extensive blog post about planets in our solar system including photos.
