National Science Teaching Association

Archive: NSTA Science Update: What is a Planet? How Scientists Classify Pluto and Other Worlds in our Solar System and Beyond, March 18, 2020

Web Seminar Archive Digital resources are stored online in your NSTA Library.

GPDWhat is a planet? Scientists who study our solar system and others think about planets in different ways. Some focus on the ways that different kinds of solar system bodies (planets, moons, asteroids, and comets) travel in their orbits, and thus define a planet based essentially on where it is. Since 2006, there has been significant professional and public debate about this concept of "planet" because such a definition was adopted as "official" by the International Astronomical Union, resulting in the famous demotion of Pluto from planet to dwarf planet status. However, many other scientists actively working in the field define a planet based not on where it happens to be, but instead on what it is like, intrinsically.

This seminar focuses on the widely-used idea of a "Geophysical Planet Definition", and how it implies that our solar system houses not just eight planets, but perhaps, truly, hundreds.

Presenters: Alan Stern, Jim Bell, Kirby Runyon, Philip Metzger

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To view the presentation slides from the web seminar and related resources, visit the resource collection. Continue discussing this topic in the community forums.

Below are comments from individuals who attended the seminar:

  • "Excellent presenters, they played off of each other well. I loved learning about the new zone, and better understanding of what makes a planet."
  • "What I found most interesting was when they mention how Astronomers have discovered thousands of exoplanets around stars."
  • "The presenters were so passionate, well-organized and knowledgeable."
  • "I found the idea of teaching science as an evolving discipline with concepts as opposed to teaching it by rote memorization to be very intriguing."
  • "This was an amazing webinar. We need to get this information out to classrooms. This is something I did not know and I am sure that there are MANY many more teachers that do not know this either."

A certificate of attendance was deposited into participants' My Profile page in the NSTA Learning Center for completing the evaluation form at the end of the program.

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