The Life Cycle of Stars

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Objective

SWBAT identify the major source of 'power' in stars as represented by nuclear fusion | SWBAT describe the life cycle of a star and identify its major "stages"

Big Idea

This multi-faceted lesson has students exploring what makes a star a star, including an in-depth focus on the process of nuclear fusion in the core of stars. Additionally, students also get a glimpse of the astronomical "life cycle" of stars in our galaxy

Lesson Introduction

In this lesson, students explore what makes a star a star, and examine how different stars in the universe are different sizes, colors, and temperatures - categorizing each of those along the way. In learning about the life cycle, we talk about nuclear fusion, the different stages of star development, and what makes big stars different than little stars...and why. As a final note, there are no additional materials or equipment required beyond the attached resources for this lesson. Have fun!

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 8.3 - Star Life Cycle (Entire Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 8.3 - Star Life Cycle (Entire Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

Do Now

10 minutes

Students come in silently and complete the (attached) Do Now. In this case, the Do Now is a review of material and some "hot standards" from previous units, as well as some content from earlier in their Astronomy unit. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material;
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. Ss a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,

It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

Introduction

10 minutes

My students had a blast working on the Introduction. In this, they take a quick minute or two to sort the nine (9) provided pictures by age. After a minute or so has elapsed, we go over them together [Note: As usual, the key for this is included in the embedded Microsoft Word document at the top of this web page in the Lesson Introduction section. Download the Word document and show the comments, and they should all pop up for you.] 

My rationale for this activity (and what I explain after we go over the answers to this) is simple - I usually ask by saying "How could you tell the older people from the younger people in this exercise?" Most students respond with something like "their size, clothing, presence of wrinkles or other facial features, etc." I then indicate that just like people, stars also have a fairly predictable life span. We know, based on specific properties like size, color, and temperature what "stage of life" the various stars in our universe and galaxy are in. Just like we have a lifespan, stars also follow a linear path from birth to death. 

Star Life Cycle Notes & Text

20 minutes

After the Introduction, we transition as a class into the Star Life Cycle Notes & Text resource. I transition to this section by indicating that just as humans have particular characteristics that make us us, what makes a star a star? I pose this question to the class, and answers traditionally tend to vary - many eventually get that it emits light (unlike planets, asteroids, or other celestial objects) - but when we transition to the notes page, they see that a star is defined as an object that conducts nuclear fusion in its core. This can only be done when there is sufficient mass and pressure to make this happen, which is why smaller objects like planets do not readily produce electromagnetic energy. 

We then transition fully to the notes, but before, I like to show them a video I really enjoy, which shows the relative sizes of various stars that astronomers have uncovered thus far (the music is a little intense, but the video is good):

Once they've seen the video, we fill in the remaining notes about nuclear fusion and the notion that mass is the key determinant of a star's life cycle. 

I then indicate that, at the point where it says Star Formation in the Star Life Cycle Notes & Text resource, students are going to be begin reading with their seat partners and answer the embedded questions on the subsequent pages (up until the practice begins on the bottom of Page 7). I give them a good amount of time (~8-10 minutes, depending on the class) to do this, before we come back together and collectively go over their responses. Here's a video of them working together on this part of the lesson.

Practice

15 minutes

The Practice section in this lesson is, like the vast majority of questions found in all of my classwork and homework, is 100% Regents-based. All of the questions come from prior Regents examinations. Likewise, as I try to generally do with all of my lessons, the questions are mostly organized to get increasingly more difficult and increase in complexity, which is why the harder questions tend to come toward the end. For whatever reason, the Regents loves to ask questions about source regions and air masses, so I truly think the practice is worthwhile, considering this is something they'll see over and over and over again in the future. 

In terms of student work habits, I tend to sometimes make this decision in the moment, and as a response of what I know about the students and how they're processing the material on, but I'll either ask them to work independently, in partners, or (sometimes) give them the option. Usually, before starting practice, we tend to go over some steps for self-help ("What should you do if you're stuck?"), and I might reference a previously used multiple-choice or free response strategy in order to build their skills while simultaneously learning content (as an example - one popular one we always use - "If you aren't sure what the right answer is, see if you can eliminate some wrong answer choices"). I tend to circulate for compliance and then hone in on specific students while they're doing this. 

After about 10 minutes, we go over their responses. Students who finish early are encouraged to work on the exit ticket (resource below) and double-check their responses. We use a combination of strategies (active voting, cold calling, popsicle sticks, volunteers) to go over the responses, where students correct their work and ask any clarifying questions. 

Exit Ticket & Closing

7 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  • Do you feel that you mastered the objective for the day?
  • Can you reiterate one thing you learned about (in this case, maybe a question about how a star's life cycle is affected by its mass or information on the characteristics of the different phases, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.