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Pluto: a planet no more

  • Key Stage 3
  • GCSE
  • Popular Activity
  • Topical

Type: Activity
Learning Strategy: Data work
Topic: Solar System

Amidst emotional scenes, the meeting of the International Astronomical Union (IAU) in Prague this summer downgraded Pluto to the new category of Dwarf Planet. In this activity, students study data on planets, dwarf planets and moons. They use the data to devise their own criteria for classifying a solar system body as a planet. Finally, they examine the reasons for the IAU's conclusion and decide whether they think the relegation of Pluto was the most logical conclusion the IAU could have come to.

11-16 How Science Works:
• 1b: how interpretation of data, using creative thought, provides evidence to test ideas and develop theories
• 3a: recall, analyse, interpret, apply and question scientific information or ideas
• 4c: how uncertainties in scientific knowledge and scientific ideas change over time and about the role of the scientific community in validating these changes

Published: 1st November 2006
Reviews & Comments: 18

Learning objectives

Students will learn that:
• astronomers collected data on solar system bodies and looked for patterns in it to devise definitions for 'planet' and 'dwarf planet'
• ideas about what planets are have changed over time as the result of new observations, more accurate data and uncertainty about data interpretation
• the scientific community – in this case the IAU – played a vital role in validating these changing ideas

Try the activity

You will need Acrobat Reader installed to open the activity sheets.

11 – 14 The solar system (KS3 QCA module 7L)
• Our solar system includes the Sun, its planets and asteroids and the natural satellites of the planets
• The planets orbit the Sun in similar ways to the Earth
• How evidence about the solar system has been collected and interpreted

Ideas and evidence in science
• About the ways in which scientists work today and how they worked in the past, including the roles of evidence and creative thought in the development of scientific ideas

14 – 16 How science works
• 1b: how interpretation of data, using creative thought, provides evidence to test ideas and develop theories
• 3a: recall, analyse, interpret, apply and question scientific information or ideas
• 4c: how uncertainties in scientific knowledge and scientific ideas change over time and about the role of the scientific community in validating these changes

14 – 16 Environment, Earth and Universe
• 8c: The solar system is part of the universe, which has changed since its origin and continues to show long-term changes

GCSE specifications

AQA Core: Radiation and the Universe - What do we know about the origins of the universe and how it continues to change?
• P1b 13.7 Observations of the solar system can be carried out on the Earth or from space

Edexcel core: Topic 12 – space and its mysteries
• P1b 12.15 Use data sources to compare the relative sizes of and distances between Earth, our Moon, the planets, the Sun, galaxies and the Universe

OCR Twenty first century core Module P1 The Earth in the Universe
• P1.1.7 Distinguish between planets, moons, the Sun, comets, asteroids and be aware of their relative sizes and motions

Running the activity

Display page 1, and ask students what they feel about the downgrading of Pluto to a Dwarf Planet. Tell them that they will interpret data to decide whether or not they agree that the decision to downgrade Pluto was the most logical decision the IAU could have made.

Divide the class into small groups. Display page 2 and give each group a set of nine cards made from page 3. Tell them to discuss the questions posed in tasks 1 and 2 of page 2. Emphasise that, at this stage, there is no one right answer to the questions of task 3 – the point of this activity is to get students to interpret data themselves and use creative thought to develop their own definition of a planet. For information, 'distance from the Sun' is given in Astronomical Units. One AU = the distance from the Earth to the Sun.

Display page 4. Go through the information here. Emphasise the dramatic scenes at the conference, and point out that some of the astronomers at the conference got very emotional. The final decision was taken by a majority vote, so whilst the consensus was that Pluto should be downgraded to Dwarf Planet status, some astronomers were unhappy with the decision and have started a petition to get it reinstated! Also point out that improved measuring and observation equipment – for example the Hubble space telescope – has been an important factor in the decision-making process. Without this equipment, astronomers would not have been able to observe solar system objects such as Sedna and Eris, so there would have been less need to question Pluto's status as a planet. For information, Eris was formerly known as 2003 UB313 and as Xena.

Finally, get students to do task 3 on page 2 – using the information on page 4 under the heading 'how can a body qualify as a planet' and the data on the cards – how confident are they that the reclassification of Pluto was the most logical action the IAU astronomers could have taken?

News links

BBC news
The news story with lots of useful links
International Astronomical Union
Report from the 2006 meeting in Prague
Orbit animations
Information about Pluto

Reviews & Comments

Write your online review to share your feedback and classroom tips with other teachers. How well does it work, how engaging is it, how did you use it, and how could it be improved?

Pluto: a planet no more review

Mar 26th, 2013

4 Star

Good activities with lots of opportunity for differentiation

Reviewer: Micaela Cuminetti


Oct 9th, 2010

4 Star

Very good activity, students sort cards by different types of data and enable less able students to be helped by more able students, as well as allowing the more able to draw in depth conclusions. Good team working activity.

Reviewer: Joanne Waters

Pluto: a planet no more review

Feb 8th, 2010

3 Star

Vert good to get groups to discuss and analyse data. Some typo's but ideas worked. Very difficult to copy some sheets as planets very small and difficult to see. I projected the sheet so all could see.

Reviewer: James Mitchell

Pluto: a planet no more review

Nov 14th, 2009

5 Star

combined this with very relevant video from Youtube - 3 clips from a horizon programme which add to the colour and put a human face on it all. Excellent feedback from an obs lesson.

Reviewer: alison Pearson


Jun 12th, 2009

5 Star

Other teachers who reviewed this lesson suggested increasing background knowledge before starting the activity. I did as suggested. I started with a short video clip on the subject of planets and dwarf planets. Students were not confused and completed the card activity on a deeper level than I believe they would have had otherwise.
Students were engaged.

Reviewer: Janice Carpenter


Jun 7th, 2009

4 Star

Very low ability group found it interesting but quite hard. Worked very weel with a better group who really enjoyed it.

Reviewer: susan humphreys


Mar 30th, 2009

5 Star

My students got really involved in this activity and some wanted to get expert involvement and went up to the local observatory to get extra information to present to the class. Wicked activity.

Reviewer: Nicky Wallace

Pluto: a planet no more review

Feb 13th, 2009

4 Star

did the activity with two year 8 groups, the high ability class got into it,

Reviewer: Louise Arnold

Yr 7 Science

Dec 2nd, 2008

4 Star

I used this with a very mixed ability year 7 group when I had lost my voice. Most groups managed the activity and enjoyed it. Recommended.

Reviewer: Maggie Ward

Pluto: a planet no more review

Sep 3rd, 2008

5 Star

This is a great card sort activity. The children particularly liked the mental image of scientists crying at the end of the conference!

Reviewer: Kelly Draper

Pluto - a planet no more!

Jul 21st, 2008

5 Star

I tried this activity with a mixed yet slightly weighted towards upper ability year 7 class at the end of Solar System and Beyond. The class loved it and all learned a bit more about how astronomers use data to check and re-check work as new information becomes available. I printed out the cards in colour and laminated them to give a more professional look and feel to the activity. I will definitely use this again!!

Reviewer: Sara Newton


Jan 18th, 2008

4 Star

Used this with both key stages pitched at different levels.
Strangely, I did not get the reaction I expected.
Year 9 (Top set) really got into the discussion and did not want to wind up at the end. Year 10 (top set) were very "so what?".

Reviewer: Michael Proudman


Sep 28th, 2007

5 Star

Really good topical piece.
Used it with the Planet Suite Pluto which was added on to Holsts work a couple of years ago.

Reviewer: Chris Boyle

Pluto - a planet no more!

May 18th, 2007

5 Star


used it in various forms with years 8 and 10.

However it did produce the question "What have they done with Pluto?" They did seem to believe me when I told them that a very large spaceship had been sent to blow it up!

Now that "My Very Easy Method Just Speeds Up Naming Planets" how about

My Very Easy Method Just Seems Uselss Now ?

Reviewer: Stephen Brian

A great lesson!

May 11th, 2007

5 Star

I used this lesson as the background for a debate with my Year 7 class. I gave them the information as homework, and sent them away to develop an argument for either reinstating Pluto as a planet or justifying its demotion.

When they came back they had the most developed and involved debate I've ever seen in a year 7 class. Really good topic, and the information presented got them thinking about it creatively.

Out of interest, my class is a mixed (but rather high) ability Year 7 class in a girls's school.

Reviewer: Joseph Bilton

Pluto - planet no more?

Feb 19th, 2007

3 Star

I did this activiity with a very low ability Year 1 group. They tackled it at a superficial level and struggled a bit. I think it would have been better if I had done a longer introduction and looked at examples of different planets and dwarf planets ahead of the activity. I shall try this approach next time.

Reviewer: Kate Balfour

Pluto past.

Nov 21st, 2006

4 Star

The exercise worked well with a high year 9 group at the end of topic 9J. However, they felt they needed more information about the other planets and dwarf planets to complete the exercise. There is useful backup information availalble on 2003UB313, now named Eris - particularly from NASA.

Reviewer: Brian Bloxham

Pluto Planet?

Nov 21st, 2006

5 Star

I did this activity with my Year 8 high ability group. It worked so well I adapted it and used it over two lessons. Most of the second lesson was for presentation of their opinions. The best thing is it can be easily adapated to be used across a whole range of ability.

Reviewer: Khumbuzo Nkunika

The upd8 store
200 lessons and assessments from as little as £4.95

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