Login or Register

800.334.5551 Live Chat (offline)

Determining the Age of a Star

A Carolina Essentials™ Activity
Deep space nebula with stars

Overview

Use this activity as a student-based or teacher-led phenomenon for a unit on stellar evolution. Using an inexpensive spectroscope with wavelength units, students determine the visible spectrum for white light, hydrogen, helium, and a hydrogen/helium mixture. Spectral analysis guides students in determining the spectral pattern of medium-sized stars like our sun.

Save & Print
Teacher Notes
Save & Print
Student Worksheet
Deep space nebula with stars
Grade & Discipline
8-12

Earth Space Science
Recommended for grades 8-12.

Time Requirements
Prep15 min
Activity20-30 min

Teacher Prep time: 15 min
Student Activity: 20-30 min

Safety Requirements
Safety gloves required.

Overview

Use this activity as a student-based or teacher-led phenomenon for a unit on stellar evolution. Using an inexpensive spectroscope with wavelength units, students determine the visible spectrum for white light, hydrogen, helium, and a hydrogen/helium mixture. Spectral analysis guides students in determining the spectral pattern of medium-sized stars like our sun.

Save & Print
Teacher Notes
Save & Print
Student Worksheet

Phenomenon

Take a CD and rotate it around under a light. What do you notice?

White light should be broken up into the spectrum.

What do you think is causing the spectrum to appear?

Students may say that the CD is acting like a prism or some type of lens. A CD is constructed of 3 layers—2 plastic and 1 aluminum. One plastic layer is burned, so there are bumps called pits and flat areas called land. A laser reads the pits and land as 1s and 0s, digitizing the medium. The burned plastic layer is coated with aluminum, making the shiny side we see. Another layer of plastic encases the aluminum. The shiny pits and land surface act similarly to a diffraction grating, which is a thin piece of plastic with many parallel slits. In both cases, the pits and slits diffract light, breaking it up into its component wavelengths.

Essential Question

How does the composition of a star like our sun change over time?

Activity Objectives

  1. Use the spectra of hydrogen and helium to identify and communicate the composition of a star.
  2. Use the spectrum of a hydrogen/helium mixture to approximate the age of a star and describe where the star is in its life cycle.

Next Generation Science Standards* (NGSS)

HS-ESS1-3. Communicate scientific ideas about the way stars, over their life cycle, produce elements.

Science and Engineering Practices

Obtaining, Evaluating, and Communicating Information

  • Communicate scientific ideas (e.g. about phenomena and/or the process of development and the design and performance of a proposed process or system) in multiple formats (including orally, graphically, textually, and mathematically).

Disciplinary Core Ideas

ESS1.A: The Universe and Its Stars

  • The study of stars’ light spectra and brightness is used to identify compositional elements of stars, their movements, and their distances from Earth.

Crosscutting Concepts

Energy and Matter

  • In nuclear processes, atoms are not conserved, but the total number of protons plus neutrons is conserved.

Teacher Preparation and Disposal

Gather student spectroscopes and ensure that the diffraction grating is in place over the slit. Inspect the spectral tubes for any signs or cracks.

Student

Teacher

  1. Student: Observe the hydrogen spectrum tube using the spectroscope.
  1. Teacher: Instruct students on the use of the spectroscope by first looking at a fluorescent or incandescent light. On the wide side of the spectroscope, point out the narrow, vertical slit and larger opening that protects the diffraction grating. Instruct students to line up the light source in the narrow, vertical slit and then move their focus to the illuminated spectrum. It is critical that the light from the spectral tube is seen in the slit. Make sure they notice the wavelength scale.
  1. Record the color bands you see, paying attention to the color, width, and brightness of each line.
  1. Place the hydrogen tube in the power supply and turn it on. Darken the room if possible.
  1. Notice the numerical scale under the color bands. Estimate the wavelength for each color band and record the wavelength in nanometers.
  1. Have students record the colors of the spectrum and the associated wavelengths in nanometers.
  1. Repeat the procedure with the helium spectrum tube.
  1. Repeat with the helium tube.
  1. Repeat the procedure with the hydrogen and helium tube.
  1. Repeat the procedure with the hydrogen and helium tube.

Data and Observations

Hydrogen Spectrum

graph showing hydrogen spectrum

Helium Spectrum

graph showing helium spectrum

Hydrogen and Helium Mix

Students may not record the exact same wavelengths for the colors they see. It’s important to notice the additional colors in helium and that the mixture of the two elements produces a combined spectrum.

Analysis & Discussion

1. Explain how the 3 spectra compare.

Hydrogen produces lines on the purple and blue end of the spectrum with one red band. Helium adds a yellow, green, and orange. The mix of elements produces a combined spectrum.

2. If a star in the same class as our sun produced a spectrum similar to helium, what you would conclude about its age?

You would expect the star to be in the old stage. Helium is the product of hydrogen fusion. The hydrogen fuel would have been used up producing the helium.

3. Explain what kind of spectrum you would expect our sun to produce in middle age.

You would expect both hydrogen and helium to appear in the spectrum. Some hydrogen would have already fused to make helium, but there would still be a supply of hydrogen. The spectrum would show both hydrogen and helium.

4. Using the spectra, illustrate the life cycle of our sun.

Young: hydrogen spectrum. Middle age: combined spectrum. Old:helium spectrum.

*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.

Carolina Kits | 3D - Explore Kit Solutions for 3-Dimensional Learning. - Explore

You May Also Like