UNIT 3 STARS & ELEMENTS

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UNIT 3

STARS & ELEMENTSHow did the stars emerge and what did they give us?

1. 2. 4. 5. 6. 7. 8. 9. 10.

UNIT 3 STARS & ELEMENTS

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3.0

STARS AND BIG HISTORY

Lesson Context

After the Big Bang, the Universe was small and incredibly hot. As the Universe expanded it

cooled, and all of the energy and atoms started to spread out into the growing space.

There were tiny variations as this happened, which created little pockets of intense

activity, resulting in small molecules. Slowly but surely, the gravity of the molecules pulled

gasses and matter together, and the first stars were born. Over time, these stars died in

massive explosions that created new elements.

Concepts

Chemical elements: Fundamental types of atoms, each distinguished by varying

numbers of protons and electrons, and each having unique physical properties. Many

elements are formed as products of dying stars.

Goldilocks Conditions: A specific set of conditions necessary to enable greater

complexity. The reference is to the fairy tale Goldilocks and the Three Bears, in which

Goldilocks looks for the porridge, chair, and bed that are “just right.”

Periodic table: The generally accepted system for organizing the known chemical

elements. Russian chemist Dmitri Mendeleev first used this method of arrangement in

1869. As new elements are discovered, they’re added to the table.

Star: A huge cloud of simple matter held together by gravity. These first complex entities

in the Universe have structure and stability, and they emit energy and light.

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Thresholds of Increasing Complexity: Moments in the history of the Universe when

specific ingredients under the right “Goldilocks Conditions” are transformed to create

something entirely new and more complex than anything that existed before. (See

Goldilocks Conditions).

Lesson Steps

Opening

Print or project this set of images detailing the life of a star (we’re assuming that you’re

using printouts, but you can easily alter the instructions for the exercise if you’re

projecting). Have students lay out the images in order from the beginning to the end of

the life of a star. At this point, the students are not presumed to have any formal

understanding of how stars form. This activity provides an opportunity to start thinking

about this process and to put their limited understanding to use. This activity should be

hands-on and very quick. Later in the lesson, they will have a chance to form a deeper

understanding of how stars form.

Timeline: Stars

Infographic

Teaching the concepts

Threshold 2 animation

Before the video…

After the Big Bang, the Universe was small and incredibly hot. But hat state didn’t last. The

Universe began to grow, and as it grew, atoms had more room to move around without

crashing into each other. Things cooled off. Let’s look at how stars formed in this cold,

dark period after the Big Bang.

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During the video…

Use these questions and prompts at the appropriate stopping point to check in with the

students and ensure they are getting the key concepts covered in the video.

0:19 What was the Universe like before the first stars formed? How long was it after the

Big Bang before stars started to form?

1:18 Why do atoms packed together tightly heat up?

After the video…

The expansion of the Universe enabled atoms and energy to spread out. This created

small pockets of activity across an otherwise empty space. In these little areas, gravity

pulled together atoms, and then more and more atoms, until the first stars came to life.

Stars attracted other stars to form galaxies. Galaxies attracted other galaxies to form

clusters, and then clusters came together to form super clusters.

Threshold 2: Stars Light Up

PDF

Threshold 2: Stars Light Up

Video

Teaching the concepts

Threshold 3 animation

Before the video…

Stars begin to light up all over the Universe. They’re not lit forever, though. Eventually,

they run out of fuel. When small stars run out of fuel, they fizzle out. Imagine a campfire

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when there’s no more wood to burn. Bigger, denser stars burn hotter. When they run out

of fuel, there are massive explosions that result in new chemical elements.

During the video…

Use these questions at the appropriate stopping points to check in with the students and

ensure they are getting the key concepts covered in the video.

1:11 Why do larger stars get hotter than smaller stars? Why is it that some elements can

only form in larger stars? (The video will elaborate on these questions in a moment, but

it’s helpful to ask students to conjecture on these points).

2:00 Question: Is there anything hotter than a star?

Answer: Yes, a supernova.

After the video…

Bigger stars--which have greater mass--burn hotter than smaller stars. The hotter the

stars, the more chemical elements are formed and the heavier those elements are. When

large stars explode (into supernovae!), things get even hotter. All the elements in the

periodic table were formed by this activity at the core of stars.

Threshold 3: New Chemical Elements

PDF

Threshold 3: New Chemical Elements

Video

Using and practicing the concepts

Ask the students to create a comic strip detailing the formation of a star. It should be at

least five panels, though students that are ready might include many more. Have students

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use the opening activity as a basis of structuring what’s happening, if that makes things

easier for them. Students may use the comic book template provided here or any simple

comic book software out on the market. Each panel of their comic should include

explanatory text. Students should end the comic when the star ignites. They will have an

opportunity to delve deeper into star formation in Lesson 3.1.

New Chemical Elements

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