Educator Guide: This Dwarf Planet Hosts an Odd Ring

An illustration of the dwarf planet Quaoar. — Dwarf planet Quaoar, shown in this artist's illustration, is only the third small object in the solar system with a known ring.

Illustration Credit: NASA, G. Bacon/STScI; Science Credit: NASA, M. Brown/Caltech

About this guide

In science, the exceptions offer researchers a chance to think differently about a concept they thought they understood. In this Guide, students will learn how astronomers use a concept called the Roche limit and how a ring around a dwarf planet does not follow the Roche limit rules.

This Guide Includes:

Why doesn’t this dwarf planet follow the rules about rings?

Students will answer questions about the online Science News article “The Kuiper Belt’s dwarf planet Quaoar hosts an impossible ring,” which describes a recent astronomical discovery that is completely counter to what scientists expected to see. A version of the article, “This dwarf planet hosts an odd ring,” appears in the March 11, 2023 issue of Science News.

Defining and defying Roche limits

Students will review force diagrams and gravitational force and discuss planetary ring and moon formation using the concept of the Roche limit. Learning Outcomes: Applying gravitational forces and interactions in space to understand ring and moon formation.