Hey everyone! Today, we’re diving into the fascinating world of planets, especially focusing on Pluto and how we classify planets in our solar system. Let’s start with a bit of history. Back in 2015, NASA’s New Horizons mission flew by Pluto, a dwarf planet located near the Kuiper Belt, which is an asteroid field surrounding our solar system. Scientists thought they had Pluto all figured out, but the images and data from this mission surprised everyone!
In 2006, the International Astronomical Union (IAU) changed the definition of what makes a planet. According to them, a planet must orbit the sun, be massive enough to be round, and have cleared its orbit of other objects. This definition excludes asteroids, comets, and moons from being planets and is why Pluto is now called a dwarf planet. So, our solar system officially has eight planets and five dwarf planets: Ceres, Pluto, Eris, Makemake, and Haumea. But did you know that there are actually 13 planets if you count the dwarf ones?
Recently, a new paper suggested changing how we classify planets. It proposed that planets should be round bodies that have never undergone fusion and have less mass than a star. If this definition is accepted, Pluto would be considered a planet again, along with Ceres, Eris, Makemake, Haumea, and 97 other objects. This would mean our solar system could have 110 planets!
Scientists care about this debate for several reasons. The current definition says planets must orbit the sun, which means that even though we’ve discovered over 1,000 exoplanets (planets orbiting other stars), there are only eight “real” planets in the universe. Some scientists find this definition too limiting.
Both definitions agree that being round is important because it excludes asteroids from being planets. However, this also means that our Moon, which is round, could be considered a planet under the new definition. The same goes for the round moons of Jupiter and Saturn!
This debate highlights the differences between planetary geoscientists, who want to explore planets physically, and astronomers, who focus on classifying and observing them. One of the main voices in this debate is Alan Stern, who disagrees with the 2006 IAU reclassification. The debate was reignited by the amazing data from Pluto and discoveries about moons like Europa, Enceladus, Titan, Io, and Ganymede.
Pluto, once thought to be a simple icy rock, is now known to have complex geological processes, possible subsurface oceans, nitrogen glaciers, a thin atmosphere, and unique interactions with the sun. These discoveries make Pluto much more interesting than we once thought.
Should Pluto be reclassified as a planet because it’s more interesting than we thought? What do you think? This debate is ongoing, and it’s exciting to see how our understanding of the universe continues to evolve.
By the way, we’ve made some changes to our show and channel. We’re now officially Seeker, focusing on science, innovation, technology, and the universe. We’ll bring you more in-depth documentaries, experiments, VR content, interviews, and science updates. Check out Seeker.com and our Facebook page for more exciting content. Share your thoughts in the comments, and if you’re curious about Pluto, watch Ian O’Neill’s video—he’s an astrophysicist and knows his stuff!
Using clay or other craft materials, create a model of the solar system, including both planets and dwarf planets. Pay special attention to the size and order of each celestial body. This will help you visualize the differences between planets and dwarf planets, and understand why Pluto is classified as a dwarf planet.
Divide into two groups and hold a debate on whether Pluto should be classified as a planet or a dwarf planet. Use evidence from the article and additional research to support your arguments. This activity will help you understand the different perspectives in the planetary classification debate.
Choose an exoplanet that has been discovered and research its characteristics. Present your findings to the class, explaining how it compares to the planets in our solar system. This will help you understand the broader context of planetary classification beyond our solar system.
Watch a documentary or video about Pluto’s geological features, such as its nitrogen glaciers and possible subsurface oceans. Write a short report on what makes Pluto unique and why these features are significant in the debate about its classification.
Work in small groups to design your own system for classifying planets. Consider factors like size, orbit, and composition. Present your system to the class and explain why you chose those criteria. This will encourage critical thinking about how scientific classifications are made.
Sure! Here’s a sanitized version of the transcript:
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Hey everyone, I know things look a bit different, but we’ll explain all that at the end, I promise. Way back in 2015, when the world made sense, NASA’s New Horizons mission flew by the dwarf planet Pluto, way out near the Kuiper Belt—an asteroid field that encircles our solar system. At the time, scientists felt they had this planet figured out. Then these images and the accompanying data from Pluto completely surprised them.
Since 2006, when the International Astronomical Union updated their classification of the word “planet,” there’s been a huge debate in the public and in the scientific community about the fate of dwarf planets. The IAU says a planet has to be a sun-orbiting body that is massive enough to be round and has cleared its orbit—meaning nothing gets in the way as it goes around the sun. This definition keeps asteroids, comets, and moons from being classified as planets, but it excludes some smaller bodies (which is why Pluto is now called a dwarf planet). So now, our solar system has eight planets and five dwarf planets: Ceres, Pluto, Eris, Makemake, and Haumea! That’s right, the current definition upgraded four other objects, and yet nobody talks about it! We have 13 planets in our solar system. “Dwarf” planets aren’t technically planets, though for some reason “giants” and “ice giants” are.
A new paper purports to change everything when it comes to planetary classification. The short paper, published in Lunar and Planetary Science, wants to reclassify planets as round bodies that have never undergone fusion and have less mass than a star. That’s it. This means Pluto would be a planet again, which is great! But it would also bring along friends; Ceres, Eris, Makemake, and Haumea would become planets as well as 97 other objects. Under this definition, our solar system would have 110 planets.
There are several reasons scientists care about this. First, the current definition says all planets have to orbit the sun. This means, even though we’ve discovered over 1,000 exoplanets, there are only eight real planets in the universe. Planets orbiting other stars aren’t orbiting the sun and so aren’t technically planets. Yes, it’s pedantic; this is science we’re talking about. Pedantry is part of the game.
On the other hand, both definitions count being round as important because it keeps asteroids out of the planetary club. But, as some have pointed out, the Moon is round. And yes, under this definition, our Moon would be a planet, as would all the round moons of Jupiter and Saturn, and elsewhere! Defining planets in the way the IAU does now is considered “flawed,” according to scientists, not just because it demoted Pluto, but it also seems unfair to discount celestial bodies that are as unique and interesting as Saturn or Venus. The researchers hope if we start recognizing Makemake, Ceres, Io, and Enceladus all as planets, maybe we’ll get the budget to explore them!
This debate really pits branches of science against each other. Planetary geoscientists want to physically explore the planets, while astronomers want to classify and observe them. One of the lead authors of this paper is Alan Stern, an outspoken critic of the 2006 IAU reclassification. This debate was reignited because of the incredible data scientists received from Pluto, plus the things we’re learning about moons like Europa, Enceladus, Titan, Io, and Ganymede. Pluto, for example, is no longer considered a boring icy rock zipping around past (but sometimes nearer than) Neptune. Instead, we know it has complex geological processes which may hide subsurface oceans, glaciers of nitrogen, a thin atmosphere, and its solar-planetary interaction is unique and unlike the eight planets in our solar system!
But does being more interesting than we thought warrant Pluto’s reclassification? What do you think? By now, you may have noticed we’ve made some changes to both the show and the channel. More changes will be happening over the next couple of weeks. We’re now officially Seeker. Seeker is all about science, innovation, technology, and the universe around us. We’ll be bringing you more in-depth documentaries, experiments, VR content, interviews, and of course, science updates from your favorite hosts. We have a lot of really exciting stuff in the works, so please subscribe, check out Seeker.com and our Facebook page, and thanks for your support. Tell us your thoughts in the comments, and if you want more incredible science about Pluto, check out Ian O’Neill’s video on it here; he’s an astrophysicist—he knows what he’s talking about.
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Pluto – A dwarf planet in the Kuiper belt, once considered the ninth planet of our solar system. – Pluto was reclassified from a planet to a dwarf planet in 2006 by the International Astronomical Union.
Planet – A celestial body moving in an elliptical orbit around a star, such as the Sun. – Earth is the third planet from the Sun in our solar system.
Solar – Relating to or determined by the sun. – Solar energy is harnessed from the Sun’s rays and can be used to power homes and devices.
System – A set of connected things or parts forming a complex whole, in particular. – The solar system consists of the Sun and all the celestial bodies that are bound to it by gravity.
Dwarf – A term used to describe a celestial body that is smaller than a planet and does not clear its orbit of other debris. – Ceres is another example of a dwarf planet located in the asteroid belt between Mars and Jupiter.
Definition – A statement of the exact meaning of a word or the nature of something. – The definition of a planet was revised to exclude Pluto, leading to its reclassification as a dwarf planet.
Orbit – The curved path of a celestial object or spacecraft around a star, planet, or moon. – The Earth completes one orbit around the Sun every 365.25 days.
Scientists – Individuals who conduct scientific research to advance knowledge in an area of interest. – Scientists use telescopes and spacecraft to study the planets and other objects in our solar system.
Moons – Natural satellites that orbit planets or dwarf planets. – Jupiter has 79 known moons, with Ganymede being the largest.
Debate – A formal discussion on a particular topic where opposing arguments are put forward. – There was a significant debate among astronomers about whether Pluto should be classified as a planet or a dwarf planet.
