Would you believe there are 40 planets are in our Solar System? If you ask the IAU - the International Astronomical Union - there are only 8, but that might not be the best possible answer. If we take a more physics-based definition of what makes a planet a planet, we might have at least 40 planets in our Solar System, and maybe many more! Learn about these forgotten planetary bodies and what makes them so amazing - with some help from New Horizons principal investigator Alan Stern. Let's explore!

Chapters:
0:00 Intro
0:20 What is a planet?
2:46 The planetary bodies
3:44 The big asteroids
4:42 The icy dwarfs
6:37 The 7 big moons
8:15 The other round moons
9:24 Conclusions

Media Credits:

Sagittarius A*: EHT Collaboration, CC BY 4.0
Kuiper Belt: by European Southern Observatory, CC BY 2.0
21 Lutetia: ESA / MPS / OSIRIS Team / Kevin Gill, CC BY 2.0
10 Hygiea: ESO/P. Vernazza et al./MISTRAL algorithm (ONERA/CNRS)
Rhea Silvia Sclupture: Sailko, CC BY 3.0
Makemake: Hubble ESA, CC BY 2.0
Haumea Ring: Kevin Gill, CC BY 2.0
Planet Nine: Kevin Gill/Elizabeth Gill, CC BY 2.0
Jupiter and moons: Jan Sandberg

End theme: "Jupiter" from Gustav Holst's "The Planets", performed by the United States Air Force Band (Public Domain)