Download Comparing Different Wavelength Pictures

Comparing Different Wavelength Pictures of Astronomical Observations
Telescopes are engineered to detect a specific range of wavelengths of electromagnetic radiation.
Images from a variety of these telescopes show different aspects of the same astronomical objects. To
trained eyes, each of the images in this collection produced contributes details that provide a more
comprehensive understanding of the observed object than is possible from a single image.
Radio images highlight the presence of cooler gas clouds (especially hydrogen)
Infrared images show areas of low-energy heat
Visible light images depict primarily gases and dust
X-ray images reveal high-energy heat emissions.
Background: Electromagnetic waves consist of oscillating electric and magnetic fields that radiate
outward at the speed of light. The different types of electromagnetic radiation given off by the Sun,
stars, and other astronomical objects are organized along a spectrum according to their wavelength, the
distance between the peaks or troughs of successive waves.
Most of the universe is invisible to us because the human eye sees only the visible light portion of the
electromagnetic spectrum. Infrared and radio emissions carry less energy per photon than visible light
and thus have longer wavelengths and lower frequencies. Ultraviolet, x-ray, and gamma-ray emissions
have shorter wavelengths and higher frequencies than visible light.
Images from telescopes engineered to detect different types of electromagnetic radiation show the
same astronomical object in different ways. Skilled observers can recognize certain properties of the
object from these images. For instance, in the case of a nebula, the gaseous remnant of an exploding
star, the color and intensity of visible light and other portions of the spectrum indicate which elements
are present and in what quantity. Infrared images provide information about planets, comets, newly
forming stars, and other relatively cool bodies. X- ray telescopes capture and show radiation from very
hot regions in stars and from violent events like explosions or collisions.
Because humans can only see the visible light portion of the spectrum, pictures that represent other
types of radiation must present information about the radiation in the visual spectral range. This
accounts for the "false" colors depicted in these images. The colors are arbitrary and are used only to
enable us to see the variation and complexity of these images.
Some telescopes, including radio and optical telescopes, can detect astronomical objects from Earth. But
because the water vapor, carbon dioxide, and oxygen in Earth's atmosphere absorb certain wavelengths
of electromagnetic radiation, other telescopes -- including those that detect ultraviolet radiation and x
rays -- must be in orbit to do their work.
By combining optical, radio, and infrared data from other telescopes with images from the Chandra Xray Observatory, which produced some of the images in this collection, new details about far-off regions
in space can be discerned. For example, some objects appear to have different shapes when viewed with
different telescopes because the types of radiation the telescopes detect originate from matter in
different places. Being able to make such composite interpretations has vastly increased our
understanding of the past, present, and future of the universe.
1. Click on downloaded program in 8E Science Handouts
2. Choose a set of pictures to compare and answer the following questions:
a. What images did you choose? Describe the different images from the different
wavelengths. Use the brief description above of the 4 wavelengths to describe your
Astronomical image.
b. Refer to the above Background information as well as your pictures to answer these:
i. Why are some telescopes used on Earth while others are launched into orbit above
Earth's atmosphere?
ii. How do the work of scientists and engineers benefit each other's areas of
expertise?
iii. What information can be obtained from a conventional photograph of a human body
that cannot be obtained from an X-ray, a thermograph — an image taken with an
infrared camera that records temperature variations on the surface of the body,
and a magnetic resonance image (MRI) — an image of internal organs and soft
tissues produced with magnetic fields and radio waves. What does the X-ray tell
that the photograph and other images do not?