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This past summer the International Astronomical Union (IAU) approved new definitions for objects in our solar system that orbit the Sun. The definitions now allow for only eight planets, while objects smaller than planets will be known as dwarf planets, and those even smaller will be referred to as small solar system bodies. Most notable of the changes was the redefinition of planet and the subsequent transfer of Pluto from planetary status to its new designation as a dwarf planet. The reasoning behind the new definitions and the reclassification of objects is illuminated in this month’s Scope on the Skies column.
This journal article did a fantastic job explaining the meaning behind Pluto no longer being a planet. Middle school students should have an enjoyable experience reading the information. It keeps you engaged and considers the idea of 11 planets. There was also the suggestion of a mnemonic device used to remember the order of the 8 planets. You will have to read this article to find out what it is.
Stephanie (Ellicott City, MD)
I throughly enjoyed this article and its explanations of terms such a dwarf planet.. It made Pluto's new designation easy to understand. The idea of 11 planets in our solar system is an interesting one. Lots of things have changed since my science project on Pluto in 1976! The dynamic nature of science is an excellent point to make with students and this article would help with that.
Cynthia Malcolmson (Severn, Maryland)
I loved this source because it was clear, concise, and more importantly, interesting! It had good background into why Pluto is no longer considered a planet.
History was made or as scientists say ‘Science is Dynamic’. The world awaited the International Astronomical Union (IAU) announcement that all though was going to name a new planet. Instead it downsized the planet Pluto to a new category called a dwarf planet. For those of us aware of this changed it was a shock and many textbooks had to be rewritten. Instead of teaching students this event, having them read this article and then making them explain what it meant might be a way to initiate self-instruction with students. What a great way to engage science with reading for meaning.
Adah (San Antonio, TX)
Review: This resource explained why Pluto was demoted to a dwarf planet very well! It also provided an explanation of what a dwarf planet is as well as questions students can answer based on the article. Finally this article showed Pluto’s statistics in relation to all the other planets’ to show how stark the contrast is between it and the gaseous planets. This is a great article for teaching the demotion of Pluto as a planet as it carries it’s explanations into the classroom. I recommend using it today!
Allison (Columbia, Maryland)
I really enjoyed this resource. I think that it is important for students to understand the re-classification process and why Pluto is no longer considered a planet. The article is relatively short and easy to comprehend, so I think that it is a very appropriate explanation. While the suggested questions are good guidelines, I think that teachers could improve upon them by adding more interacting components instead of just simple, straight-forward comprehension questions. Perhaps teachers could ask students their thoughts/ opinions/ predictions for the future. Overall, I think that this is a great resource to use as long as it is paired with other resources and adapted slightly for your particular class.
This short, 3 page, article gives a direct and concise explanation of categorizing solar system objects that circle the Sun into 3 categories: planets, dwarf planets, and small solar system bodies. A detailed chart featured as part of the article provides specific orbital information for each. Helpful to a teacher is the section “Questions for Students”. These could be used to base classroom instruction upon, or as a self-directed study for the more advanced middle school student.
This article is useful because it is an explanation of the reasoning behind the redefinition of planet. It also explains what a dwarf planet is and a small solar system body. It gives a new mnemonic device to remember the planets, “My Very Entertaining Mother Just Served Us Noodles,” which is good for elementary teachers to help their students remember them. The best resource in this article is a chart which gives information such as the planets and other solar system objects’ IAU designation, diameter and more.
This resource is fantastic! And it is completely free to members! It is only $0.99 for nonmembers, very convenient for teachers! This resource discusses in great detail the new definitions for what constitutes a planet, and why Pluto no longer falls into the category of a planet, hence the title of the journal. This is a great resource that can also be used in the classroom. Students can read articles in this journal to learn about why Pluto is not a planet, and instead what the ex-planet can be defined as.
Kimberly Forrester (, )
This seems like a fantastic up-to-date resource for students and teachers to learn about the newly defined definitions for what constitutes a planet.
As a student who grew up learning that their were nine planets instead of eight, I sometimes catch myself still telling people Pluto is a planet. What I really liked about this source is that it explained the incredibly foreign concept of dwarf planet to me. I feel much more confident now that I can explain why Pluto is no longer a planet and also what dwarf planets are.
I thought that this was a great article explaining the reasoning behind Pluto not being a planet anymore. Also, the student questions were great, as well. its definitely something I can use in the classroom for older students when discussing about the planets and solar system.
Angela Cho (Ellicott City, MD)
I grew up with the knowledge that Pluto was the ninth planet, so I was a bit shocked when I learned it was no longer categorized as such. This article is a great read for someone interested in learning more about why Pluto is no longer considered a planet. Riddle describes the differences between planets, dwarf planets, and small solar system bodies. There is also a figure included that lists the size, category, and distance from the sun for each planet, dwarf planet, and small body in our solar system. This would be helpful for creating a visual aid that demonstrates the difference between Pluto and other planets. It is a short, concise, and informative article!
Growing up in the 90's, I will forever know Pluto as the ninth planet. When learning about the planets, I was always taught the mnemonic, My Very Educated Mother Just Showed Us the NIne Planets which I still use today regardless of what recently happened. Nowadays, it's interesting how the new standby mnemonic has changed as well. Nevertheless, this article was definitely an interesting read. I never really understood why Pluto had to be classified as a dwarf planet, so this was an insightful reading. It is also useful for teachers because it even includes a "Question for Students" section and displays a chart of the planets and dwarf planets and how they compare with each other. Overall, this article definitely helped explain the reasoning for Pluto's new classification in way that teachers can explain to their own students as well.
Susan (Columbia, MD)
Overall, I felt that this was a comprehensive source for both teachers and students. Not only was the categorization system clearly explained, definitions were also explicitly stated to make the concepts easier to grasp. One improvement I could see for students using this source is some kind of model on the .pdf that shows pictures comparing the size of the planets, dwarf planets, and solar system bodies.
Marianne Blemly (Ellicott City, Maryland)
I think that this is appropriate for a middle school setting. I do think that you have to modify this lesson for elementary age school children. Overall I found it helpful.
Constance Powell (, )
I went through elementary, middle, and high school being taught that Pluto was the ninth planet in the solar system. The change to Pluto’s planetary status took place while I was in my undergraduate year and I never really knew the exact reason why Pluto was downgraded as a planet. This article, published in January 2007, finally gives a clear reason for the demotion. It explains the properties and orbits of objects in the solar system and how these objects are now classified based on these properties. It is a concise, yet detailed article that summarizes the new system of categorizing solar system objects. I also liked the questions based on the figure at the end of the article that teachers can use in the classroom to help students learn more about the new way the solar system objects are defined.
This article deals with the new definitions for objects in our solar system. Specifically, a planet has changed to a dwarf planet, asteroids have also changed to dwarf planets, and many other objects have been categorized as small solar system bodies.
The article says that the goal of all this is to acknowledge newly discovered and potential future discoveries of TNOs (Trans Neptunian Objects, which are Solar system objects that have orbits ranging from the orbit of Neptune outward.
The article states that another goal of reclassification is give more clarity to how solar system objects
are grouped based on properties and orbits.
The next section details how planets are classified. I learned that Mercury) has the only orbit that is not almost perfectly circular. We also learn about the Perihelion (a planet’s minimum distance from sun) and the Aphelion (a planet’s maximum distance from sun).
Now Dwarf Planets are covered and information is given about the new dwarf planets and some history regarding them.
Finally, the article covers small solar system bodies. These include all other objects in the solar system with orbits around the sun, including asteroids, comets, and many TNO’s. Information is given about a few of the small solar system bodies including teaching us that the Oort Cloud is considered to be the source of comets that come into the inner solar system.
Questions are then provided to give your students which involve conducting further research, making connections, and using information attained from reading the article to answer questions.
There are also official names and orbital information given for all 15 planets, dwarf planets and small bodies. These are presented in a chart-form.
A random list of moon events is given for the month of January, which I am unsure as to why they included.
I would have liked an article titled “And then there were 8” to have a lot more detail about the history of Pluto the planet, and the ins and outs of it being declassified as a planet and reclassified as a dwarf planet.
Based on the content of the article, I believe the title is inappropriate, and should be altered to something along the lines of “The reclassification of our Solar System.”
I was looking to this resource for more information on the IAU’s new definitions for solar system objects, which resulted in the “demotion” of Pluto to a dwarf planet. Pre-service teachers in my science methods class were intrigued by this recent development, so I assume it’s a hot topic in science classrooms as well. I was hoping to understand what sets Pluto apart from the other eight planets, but the author uses so much technical vocabulary and includes so many figures that I came away more confused instead. He does include a chart comparing data about planets, dwarf planets and solar system bodies, which did aid my understanding. But overall I felt the reader would need to be relatively knowledgeable about the solar system already to full understand the text. In my case, I would need to consult additional resources in more layman’s terms to feel comfortable explaining this development to elementary school students.
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