For centuries, we have gazed at the night skies, wondering at the specks of light scattered across the darkness, seeking ways to explore the cosmos. Spacecrafts and landers continue to explore our solar system. However, until these missions can bring pieces of solar system objects back to Earth, we will not have direct samples of other worlds, with the exception of several pounds of Moon rocks and the meteorites that fall from the sky. Therefore, we learn almost everything about our vast universe remotely through studying light. Collecting and analyzing light, the electromagnetic spectrum, is our key tool for exploring the universe beyond our nearest neighbors in the solar system.
By exploring the electromagnetic spectrum with powerful new and specialized telescopes, scientists can tackle some of the most fundamental human questions: “Where did we come from?” and “Are we alone?” NASA’s Astronomical Search for Origins program uses tools of astronomy to seek answers to these questions and more. Current and future Origins missions (see “On the Web”) are designed to explore the universe at infrared, visible, and ultraviolet wavelengths in search of evidence that reveals the origin and evolution of the universe, stars, galaxies, planets, and life. From these missions, educational and outreach programs are developed to peak students’ natural curiosity about space and motivate interest in fundamental science concepts.
Extending human vision
Throughout history, most astronomy has been done at visible wavelengths, first with the naked eye, and then with instruments designed to enhance our vision. Astronomical telescopes extended human vision to see dimmer and more distant objects, always in the same light that the human eye senses. The resulting discoveries changed our view of the universe and our place in it. In 1609–1610 Galileo discovered the moons of Jupiter, craters on our own moon, spots on the Sun, the phases of Venus, and the multitude of stars that comprise the Milky Way. Over the next three centuries, larger and better telescopes were constructed, and astronomers demonstrated that the Earth orbits the Sun, and that the Sun is not at the center of the “universe” (as our Milky Way galaxy was then known).
In the early twentieth century, Edwin Hubble used the most powerful telescope of his day to discover the other “island universes” we now call galaxies. The Milky Way became one of many galaxies in a vast expanding universe. At the same time, a variety of instruments that attach to telescopes were created and they supplanted the human eye as the primary tool for observing the sky and vastly extended our view of the universe beyond the range of visible light. For example, in addition to cameras that take images of celestial objects, astronomers use spectrographs to separate light into its component wavelengths. Features in the resulting spectrum help astronomers measure an object’s properties, such as its temperature, composition, density, and motion. By using the tool of spectroscopy, we have identified organic molecules in the gas and dust between the stars, found that water is common throughout the universe, discovered more than 100 extrasolar planets, and measured the expansion of the universe.
Each of these discoveries occurred as larger and newer telescopes and affiliated technologies gave us a more detailed view of the near and distant cosmos. Although early astronomical discoveries relied on visible light, modern telescopes probe the universe across the continuum of the electromagnetic spectrum from low- energy radio wavelengths, through infrared, visible, ultraviolet, x ray, and gamma ray energies. Each type of electromagnetic energy reveals important clues about the nature of our universe, from the first detection of the glow of the Big Bang at radio wavelengths to the discovery of black holes and other exotic phenomena at x ray and gamma ray wavelengths.
Tools of astronomy
Using ground and space-based telescopes, along with innovative technology and interdisciplinary research, NASA’s Astronomical Search for Origins missions seek to understand how today’s universe came to be and what its future may be. Powerful new telescopes will allow us to detect faint infrared light from the earliest stars and galaxies in the universe. These telescopes will probe the skies collecting evidence about the environments where new stars and planets form. Characteristic features in the spectrum of light emitted by atoms and molecules—spectral “fingerprints”—will allow us to identify the chemical elements and molecules in the nearby and distant universe and to search for indicators of life on other planets, such as oxygen, ozone, and methane. We will search for terrestrial planets beyond our solar system by measuring the light from stars with high precision.
Through the integrated science of astrobiology, scientists are seeking to understand the history of life on Earth and the conditions needed for life, while astronomers are designing and constructing the telescopes that will reveal whether other planets exist that might sustain life. Our quest for knowledge takes us from the most extreme environments on Earth to the distant stars and galaxies; from the biology of life to the geology of nearby planets; and from the chemistry of interstellar atoms and molecules to the physics of the early universe. The key to this exploration is collecting and analyzing, and making sense of the information that arrives from the near and distant universe as electromagnetic energy, as light.
From NASA to the classroom
To help communicate the excitement and results of “Origins” research in a manner directly relevant to the needs of the K–12 education community, NASA’s Office of Space Science has created the Origins Education Forum—a consortium of the individual education and public outreach programs conducted by each Origins mission, including NASA’s Hubble Space Telescope. By surveying NSTA convention attendees, Hubble Space Telescope’s Formal Education Program found that curriculum support tools focusing on the electromagnetic spectrum are among the most frequently requested educational materials. In light of these data, the importance of the electromagnetic spectrum in the exploration of our universe, and the National Science Education Standards (NSES), the forum and its member missions have created materials to support education in this area.
The Electromagnetic Spectrum poster (see insert) features images of the Whirlpool Galaxy obtained by a variety of telescopes (including Hubble) at energies throughout the electromagnetic spectrum. The poster’s classroom activities build on students’ personal observations of light and color from the natural world, involving students in direct experiences with both visible and “invisible” regions of the electromagnetic spectrum. The activities support the NSES Physical Science: Content Standard B: Interactions of Energy and Matter (NRC 1996, p. 180) for grades 9–12.
One such classroom activity—“Chemical Detective” (see activity below)—can be used in conjunction with The Electromagnetic Spectrum poster. Drawing upon chemistry, biology, geology, and other disciplines in addition to physics and astronomy, the breadth of Origins science provides a unique opportunity to frame classic activities for use in the integrated science classroom. Chemical Detective provides an example of how the properties of the electromagnetic spectrum can be used in an inquiry-based chemistry setting, as students are led from the familiar, continuous spectrum of white light to the discrete spectra of other light sources.
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Chemical Detective activity
Objective
Students identify substances based on the visible spectra they emit, gaining familiarity with discrete spectra and their relationship to chemical elements.
Materials
- Overhead projector, holographic diffraction grating, and two pieces of 8” × 10” dark paper;
- Hand-held diffraction gratings or hand-held spectroscopes;
- Various light sources (light sources with a long thin tube or filament are easier to view):
• incandescent bulb (creates a continuous spectrum);
• fluorescent tube (coated tubes yield a seemingly continuous spectrum);
• “black light” tube (uncoated tube for creating a discrete spectrum);
• two or more gas spectrum tubes for different elements, include neon if possible (gas spectrum tubes create discrete spectra); and
• gas spectrum tube power supply;
- Activity Sheet A: “Visible spectra for chemical elements” (Figure 1);
- Activity Sheet B: “Chemical Detective” (Figure 2);
- Colored pencils, markers, or crayons.
Safety
Caution students not to touch the light sources as they may be hot and the gas tubes use high voltages. Students should not insert the gas spectrum tubes in the power supply or change the gas spectrum tubes. Students should not stare directly at the light sources for extended periods of time.
Procedure
In a darkened room, use the overhead projector, the holographic diffraction grating, and the two pieces of dark paper to project a continuous color spectrum on a wall or screen following the detailed instructions given in “The Visible Spectrum” activity on the back of The Electromagnetic Spectrum poster. (Instructions are also available on the Active Astronomy website, see “On the Web.”) Ask students to describe what they see and make a colored drawing. Students may compare the spectrum with a rainbow or with light seen through a prism or crystal. If desired, explain that the diffraction grating separates the light according to wavelength.
Show students the incandescent light source, the black light source, and one of the gas tubes other than neon. (To work with gas spectrum tubes, follow the manufacturer’s directions. Gently insert the tube into the power supply. Then, briefly turn the power supply on to illuminate the gas. Turn the power supply off immediately after student viewing to prolong the life of the tube.) Briefly turn on each source so students can see the color of the light, while instructing students not to stare directly at the light sources for long periods of time. Turn each source off after it has been viewed. Ask students to list three to five questions they have about what they see. Discuss that they will use the diffraction gratings (or spectroscopes) to view the light from each source and ask them to predict whether each light source’s spectrum will be similar to or different from that of the overhead projector
The activity
1. Give students hand-held diffraction gratings or spectroscopes. In a darkened room, allow students to view the incandescent source through their gratings (or spectroscopes) and to record their observations. Students should reconfirm that white light can be diffracted into a continuous color spectrum as was demonstrated at the beginning of the activity. Next have them view the sources that produce a discrete spectrum (the black light and one of the gas tubes, saving the neon tube for step 2 below). Briefly turn each light source on for student viewing, then off. Ask students to draw the spectra they see and explain how the spectra produced by the black light and the gas tube differ from the one produced by the incandescent light. Encourage them to describe any relationship that might exist between the colors viewed in the spectrum and the appearance of the light source to our eyes (white light has all colors; black light has purple, blue, and green but not much orange or red; a hydrogen tube looks purple and has purple, blue, and red).
2. Ask students to consider fingerprints and discuss why they are important in identifying individuals. Spectra are analogous to fingerprints: Each chemical element and molecule produces a unique pattern of spectral lines. This pattern of lines can be used to identify the presence of a particular element or molecule in an unknown substance. Without telling them its identity, illuminate a neon gas tube. Encourage students to guess what is inside the tube and to predict what the spectrum will look like (e.g., discrete or continuous spectrum; colors that may be present) and have them justify their predictions. Students may then view the neon gas tube through their diffraction gratings or spectroscopes and record the number of spectral lines they view and the color of each line. Ask students to compare the relationship between the colors of the spectral lines and the color of the light our eyes see (most of neon’s emission lines in the visible range are red and orange, so neon appears red). Give students a copy of Figure 1 showing visible spectra for various elements and have them match the lines they see from the neon gas tube to the chart.
3. Have groups of students share the list of questions they generated in “Setting the stage” and choose one question. Ask students to write a short paragraph describing how they would use a diffraction grating or spectroscope to answer this question. Then involve them in carrying out their experiments, recording their results, and explaining how their question was answered using the diffraction grating or spectroscope.
Assessment
Arrange students into new groups. Give each group a copy of Figure 2. Have each group work as a team to solve the mystery and submit a written report discussing their solution, the evidence they gathered that led them to the solution, and how they used spectroscopic techniques to solve the crime. Consider stressing that more than one “criminal element” was involved. Note that the “aliases” of the criminal elements are their chemical symbols, and the “perpetrators” are argon and sodium.
Reinforcing concepts
The light that we see with our eyes represents only a small portion of the electromagnetic spectrum. Developing the technology to detect and study other portions of the electromagnetic spectrum has had a tremendous impact on astronomy, where scientists must use the properties of light to learn about objects that are too far away to visit.
NASA educational materials use astronomical data and the excitement of space exploration to reinforce fundamental science concepts such as the electromagnetic spectrum and motivate interest in science and technology. |
Denise Smith (e-mail: dsmith@stsci.edu) is the forum scientist for the Origins Education Program and Bonnie Eisenhamer (e-mail: bonnie@stsci.edu) is manager of the Hubble Space Telescope Formal Education Program, both at the Office of Public Outreach, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; Edna DeVore (e-mail: edevore@seti.org) is codirector of the education and public outreach programs for the Stratospheric Observatory for Infrared Astronomy and Kepler missions, and the director of education and outreach and the deputy chief executive director at the SETI Institute 2035 Landings Drive, Mountain View, CA 94043; and Luciana Bianchi (e-mail: bianchi@pha.jhu.edu) is a principal research scientist at Johns Hopkins University, a coinvestigator on the GALEX mission, and the education and public outreach lead for the Far Ultraviolet Spectroscopic Explorer mission, 3400 North Charles Street, Baltimore, MD 21218.
Reference
National Research Council (NRC). 1996. National Science Education Standards. Washington, D.C.: National Academy Press.
On the Web
Visit the following websites for additional information about the electromagnetic spectrum and spectroscopy:
Additional classroom resources are available at these NASA Origins mission sites: