Investigation Driving Question

How are stars different from each other?

Storylines

The storyline process is intended to be student-driven and connect lessons within the unit. The Stellar Safari investigation, including this phenomenon, would fit best into unit storylines geared toward understanding the properties of stars including the Sun.

Possible storylines include:

• What determines the rate and types of fusion in stars and how does the fusion rate create specific stellar properties?

• How do the characteristics of the Sun (such as lifetime, temperature, luminosity or size) compare with the properties of other main sequence stars?

• How do stars like the Sun evolve as they age? What causes the changes?

• How can star clusters be used to study the relative properties of a group of stars?

• How can the distance and age of a star cluster be determined?

Instructions for Introducing Phenomenon

Arrange a Driving Question Board

Before class starts, arrange a Driving Question Board (DQB) to be used during class. The board should be visible to all students. This can be created using sticky notes or in a digital format (see other resources here). The DQB should include the investigation driving question, “How are stars different from each other?” Students will revisit the DQB throughout the lesson to expand upon their original understandings and ask questions to better explain the supporting phenomenon. If you have a driving question for the unit or have already created a DQB board, this investigation driving question can be used as a sub-question.

Print Star Cards

Print the star card sets listed below. Students will be working in small groups for this activity. There are three different sets of star cards. Print enough sets of star cards for each group to have one set.

Introduce the Phenomenon

1. Explain to the students that they will be going on a stellar “safari”, observing and gathering information about stars (rather than animals).

2. Place students in small groups and give each group a set of star cards. When each group receives their cards, they should begin observing their stars, looking for patterns.

3. Next, give students five minutes to work with their group to organize their set of stars. There are no restrictions or guidelines for how they should organize their stars. You can encourage groups to be creative or to consider prior knowledge.

4. After five minutes, or when the groups are finished organizing their set of stars, go on a gallery walk around the room as a class. As you stop together at each group, ask the group to explain to the class how they organized their set of star cards. Optional: after the gallery walk, challenge students to find a new way to organize their star cards.

5. After the gallery walk, present the students with the investigation driving question, “How are stars different from each other?” Hold a class brainstorming session with students working dynamically on whiteboards and sticky notes to share ideas or responses to the driving question. Encourage students to think about some of the properties they saw on their star cards. Then facilitate a class discussion, identifying common themes.

6. Then, ask students to individually generate questions that will lead to further investigation of this topic. Students should place their questions on the driving question board. Work with the students to organize the driving question board by common themes in the questions. Examples:

7. Explain to students that they will be completing an investigation that will help them answer this driving question and the questions they have generated. If questions remain after the investigation, encourage independent study to explore these questions further.

8. Begin the Stellar Safari Investigation.

After the Investigation - Making Sense of the Phenomenon

Begin by printing the star cluster CMDs with fitted isochrones. Each group should have their own set of CMDs. The star cluster CMDs should not be labeled.

1. Hold a class discussion as students look back at the remaining questions on the DQB. What questions can we answer? What additional questions do you have? Encourage students to independently investigate any remaining questions they have.
2. Ask students to work in their small groups and revisit their star cluster CMD from the first checkpoint of the investigation. Or, ask students to organize their star cards (or a new set of star cards) according to the axes of a CMD.
3. Provide students with each of the star cluster CMDs (not labeled).
4. Ask students to work with their groups to analyze the isochrones for each cluster and determine which CMD represents their star cluster.
5. Ask students to then explain the evolutionary state of their star cluster using the turn off point of the isochrone as their guide.
   The evolutionary states of the star clusters will vary. Explanations should include details about the mass of the main-sequence stars near the turnoff points. The lower the turnoff points, the older the star cluster.

Published ages of the star clusters:

• NGC188 Cluster 1 - 9.7 Gyrs
• NGC2323 Cluster 2 - 8.3 Gyrs
• NGC2369 Cluster 3 - 9.0 Gyrs

Youngest to oldest: Cluster 2, Cluster 3, Cluster 1