Should Pluto be a planet again?
Science Friday Podcast Recap
Published:
Duration: 19 min
Guests: Dr. Amanda Bosch, Dr. Alan Stern
Summary
The episode revisits the debate over Pluto's planetary status, highlighting differing views among scientists and the public. Key insights include the scientific basis for classifying planets and the implications of Pluto's status in the broader context of astronomy.
What Happened
Pluto's planetary status has been a source of contention since the International Astronomical Union (IAU) redefined what constitutes a planet in 2006, leading to Pluto's reclassification as a dwarf planet. This decision was largely based on the criterion that a planet must have cleared its orbit, something Pluto does not do due to its resonance with Neptune.
Jared Isaacman, NASA Administrator, has reignited the debate by suggesting that Pluto should be reinstated as a planet, a sentiment previously echoed by former NASA Administrator Jim Bridenstine. Both Dr. Amanda Bosch and Dr. Alan Stern argue that most planetary scientists consider Pluto a planet, despite the IAU's decision.
Dr. Alan Stern criticizes the IAU's vote, stating that scientific consensus should not be reached through voting but rather through individual expert analysis and consensus. He argues that the current definition excludes many celestial bodies, which is contrary to how other scientific classifications, like elements on the periodic table, are handled.
Dr. Amanda Bosch emphasizes the significance of Pluto's discovery at the Lowell Observatory and its cultural and scientific importance. She notes that Pluto was declared Arizona's state planet in 2024, underscoring its special place in public sentiment.
The New Horizons mission to Pluto revealed it to be an active and complex world, with features like mountain ranges and glaciers, challenging previous perceptions of distant celestial bodies. This mission reignited public interest in Pluto and raised questions about the criteria used to define planets.
Dr. Stern argues that dwarf planets should be considered planets, similar to how dwarf stars are still considered stars. The variety of planets, both in our solar system and beyond, suggests that a broader definition could be more scientifically robust.
Recent discoveries of thousands of exoplanets around other stars have shown that our solar system is not the only configuration. These discoveries suggest that planets are more common than stars and that a wide range of planetary types exist, many of which don't fit neatly into our current definitions.
Both guests highlight the need to focus not on what makes a planet a planet, but on the diverse characteristics that define different types of planets. This includes factors like atmospheres, satellites, and potential for life, which are becoming increasingly important in planetary science.
Key Insights
- The IAU's definition of a planet, which excludes Pluto, was decided by a vote in 2006 and is controversial among many planetary scientists. This decision was based on the criterion that a planet must clear its orbit, a condition Pluto does not meet due to its orbital resonance with Neptune.
- The New Horizons mission in 2015 revealed Pluto to be a geologically active world with features such as mountain ranges, glaciers, and an atmosphere. These findings have challenged previous assumptions about distant celestial bodies.
- Exoplanet discoveries have shown that planets are more common than stars, with a variety of types and configurations not seen in our solar system. These include Hot Jupiters and super-Earths, expanding our understanding of what planets can be.
- Dr. Alan Stern argues that the term dwarf planet should not exclude such bodies from being considered planets, similar to how dwarf stars are still classified as stars. This perspective is shared by many planetary scientists who advocate for a broader definition of planets.