Objectives (5 - 7 minutes)

1. Understand the concept of the Astronomical Unit: Students should be able to explain what an astronomical unit is, how it is defined, and how it is used in astronomy to measure large distances in the Solar System.

2. Apply the knowledge of the Astronomical Unit in practical problems: Students should be able to use the astronomical unit to solve problems involving the distance between planets, the distance between Earth and the Sun, and other related concepts.

3. Relate the Astronomical Unit to the Solar System: Students should be able to understand how the astronomical unit fits into the study of the Solar System, and how it is used to measure and compare distances between celestial bodies.

Secondary Objectives:

• Develop critical thinking skills: Through the study of the astronomical unit, students should also be encouraged to develop critical thinking skills, such as the ability to analyze and solve complex problems.

• Stimulate interest in astronomy: The topic of the astronomical unit, which involves the exploration of space and our solar system, can be a great opportunity to spark students' interest in astronomy.

Introduction (10 - 15 minutes)

1. Review of previous concepts: The teacher should start the lesson by briefly reviewing the concepts of the solar system, planets, and their orbits around the Sun. This is essential for students to understand the need for a unit of measurement like the Astronomical Unit. The teacher can ask students questions to check their understanding of these concepts and clarify any possible doubts.

2. Problem situations: The teacher should propose two problem situations to arouse students' curiosity and demonstrate the relevance of the topic:

   • Situation 1: "If we wanted to send a probe to Mars, how could we calculate the distance it would have to travel? How could we compare this distance to the distance between Earth and the Moon?"
   • Situation 2: "If we wanted to send a spacecraft to the nearest star to the Sun, Proxima Centauri, how could we calculate this distance? How could we express this distance in a unit that makes sense to us?"

3. Contextualization: The teacher should then contextualize the importance of studying the Astronomical Unit, explaining that this unit of measurement is essential for space exploration, allowing scientists and astronomers to calculate distances between celestial bodies and plan space missions.

4. Introduction of the topic: The teacher should introduce the topic of the Astronomical Unit, explaining that it is a unit of measurement that represents the average distance between Earth and the Sun. The teacher can share curiosities about the Astronomical Unit, such as the fact that it was initially defined as the distance between Earth and the Sun at aphelion (when Earth is farthest from the Sun in its elliptical orbit) and that, despite having undergone some alterations, the current definition is very close to the original one.

5. Capture students' attention: To capture students' attention and spark their interest in the topic, the teacher can share some practical applications of the use of the Astronomical Unit. For example, the teacher can mention that the Astronomical Unit is used to measure distances between other objects in our Solar System, such as the distance between Earth and the Moon. Additionally, the teacher can mention that the Astronomical Unit is used to define other astronomical units of measure, such as the Parsec and the Light-year, which are used to measure intergalactic distances.

Development (20 - 25 minutes)

1. Modeling Activity - "Building the Solar System to Scale": The teacher should divide students into groups of 3 to 5 and provide each group with a sheet of paper, a pencil, and a ruler. The goal of the activity is for students to build a representation of the Solar System to scale, using the Astronomical Unit as a reference for the distance between planets and the Sun.

   Activity steps:

   • Step 1: The teacher should explain to students that they will build the Solar System on a scale where the Astronomical Unit will be represented by a certain measure (e.g., 1 cm).
   • Step 2: Each group should choose a planet (or the Sun) to start. They should research the average distance of that planet from the Sun in Astronomical Units (AU) and then calculate the corresponding distance in the chosen scale.
   • Step 3: Using the ruler and pencil, students should mark the calculated distance on the sheet of paper, starting from the "Sun" (a drawn circle on the paper).
   • Step 4: Repeat steps 2 and 3 for the other planets, always observing the chosen scale.
   • Step 5: After marking the distance of all planets, students should draw circles representing the planets, with sizes proportional to their actual sizes.
   • Step 6: At the end of the activity, each group will have built a representation of the Solar System to scale, where the Astronomical Unit was used to measure the distances between the planets.

2. Problem-Solving Activity - "Space Mission": The teacher should propose a practical problem involving the use of the Astronomical Unit. For example: "Imagine you are the chief scientist of a space mission to send an exploration probe to Jupiter. How would you calculate the distance between Earth and Jupiter in Astronomical Units?" Students should then discuss in their groups and present the solution to the class. The teacher should guide the discussion, questioning students about how they arrived at their answer and encouraging them to relate the activity to the concept of the Astronomical Unit.

3. Discussion Activity - "The Importance of the Astronomical Unit": The teacher should lead a classroom discussion on the importance of the Astronomical Unit in astronomy and space exploration. The teacher can ask students how they think space exploration would be different if we did not have a unit of measurement like the Astronomical Unit. The teacher should guide the discussion, reinforcing the points raised by students and adding additional information if necessary.

These activities will allow students to apply the concept of the Astronomical Unit in practical contexts and reinforce their understanding of the concept.

Return (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes): The teacher should gather all students and promote a group discussion about the solutions or conclusions found by each team during the modeling and problem-solving activities. The teacher should encourage students to share their experiences, questions, and discoveries, and to explain how they applied the concept of the Astronomical Unit in each activity. This will allow students to learn from each other and see different ways to approach and solve problems related to the Astronomical Unit.

2. Connection to Theory (2 - 3 minutes): After the discussion, the teacher should make the connection between practical activities and theory. They should highlight how the activities illustrated the application of the Astronomical Unit and how they allowed students to visualize and better understand the vast distances in the Solar System. For example, the teacher can show how the scale used in the modeling activity allowed students to visualize the vastness of space and the relative proximity of planets in the Solar System. This connection will help consolidate students' understanding of the concept of the Astronomical Unit.

3. Individual Reflection (2 - 3 minutes): Finally, the teacher should suggest that students reflect individually on what they learned in the lesson. The teacher can ask questions like:

   1. "What was the most important concept you learned today?"
   2. "What questions have not been answered yet?"
   3. "How can you apply what you learned today in other situations?"

   The teacher should give a minute for students to think about these questions. Then, they can ask some students to share their answers, which can help identify any persistent misunderstandings and highlight the key lessons learned.

This Return stage is essential to consolidate students' learning, allow them to reflect on what they have learned, and identify any areas of confusion or doubt. Additionally, it provides valuable feedback to the teacher on the effectiveness of the lesson and any adjustments that may be necessary for future lessons on the same topic.

Conclusion (5 - 7 minutes)

1. Summary of Contents (2 - 3 minutes): The teacher should start the Conclusion of the lesson by summarizing the main points covered during the lesson. They should remind students about the concept of the Astronomical Unit, how it is defined, and how it is used in astronomy to measure distances in the Solar System. The teacher can also briefly review the activities carried out, highlighting the importance of each in understanding the concept.

2. Connection of Theory with Practice (1 minute): Next, the teacher should reinforce the connection between theory and practice. They should highlight how the modeling and problem-solving activities allowed students to apply the concept of the Astronomical Unit in real contexts, and how this contributed to the consolidation of learning.

3. Suggestion of Extra Materials (1 - 2 minutes): The teacher should then suggest extra materials for students who wish to deepen their knowledge of the Astronomical Unit. These may include books, documentaries, websites, and astronomy apps that offer additional information on the topic. For example, the teacher can recommend the use of an augmented reality app that allows students to explore the Solar System to scale and visualize the distances between planets in Astronomical Units.

4. Importance of the Topic in Everyday Life (1 minute): Finally, the teacher should emphasize the importance of the topic in everyday life. They can explain how the Astronomical Unit, despite being an astronomical unit of measure, has practical applications and is crucial for space exploration and our understanding of the universe. The teacher can also mention how the study of the Astronomical Unit helps develop critical thinking skills and curiosity for science and the world around us.

This Conclusion will provide students with a recap of the main points learned, guidance to deepen their knowledge, and a clear understanding of the relevance of the topic to everyday life and science.