to Videolink arrow

Newton logo to print

Galaxy Mapping

 

Overview

Edwin Hubble's proof that the universe is dynamic and that our Milky Way is not the lone galaxy provoked a renewal of questions and theories. Understanding the positions, distances, and distribution patterns of other galaxies not only provides mapping information; it gives perspective on what the earth's relationship is to the overall universal plan; it provides clues about the earth's origin; and it gives a type of structure to an indistinct concept. The Doppler effect can explain the red shifts found in the light from galaxies. According to the Doppler effect, the more that light is shifted to longer wavelengths (meaning toward the red end of the spectrum), the faster the source of the light is moving away from the observer. Edwin Hubble found that the farther away the galaxy, the more its light is red-shifted. This means that the farther the galaxy, the faster it is moving away from us. In other words, the universe is expanding. Consider the universe as a huge ball of bread dough, speckled throughout with raisins, each raisin denoting a galaxy. There is no definite boundary or edge, however. As this model universe is baking in the oven, yeast is making the dough expand. The expanding dough carries the raisins farther and farther apart from each other, but the size of each raisin does not increase. In the same way, space expands the distance between galaxies in the universe, but the galaxies themselves do not get larger. We are on the threshold of new discoveries about the galaxies. Using the latest technology, Margaret Geller and John Huchra are able to analyze "slices" of the universe. If the ball of raisin-bread dough represents the universe, Geller and Huchra so far have mapped only four very thin slices of bread that don't even go all the way through the loaf. Their mapping illustrates a definite pattern to galaxy distribution. Galaxies appear to be positioned in a network of thin, curved walls that surround huge, nearly empty voids. How empty the voids are and how they arose, no one yet knows. The "Great Wall" of the universe is the largest structure known to humans, yet its size, 500 million light years by 200 million light years , poses a challenge to cosmological theories. No one can explain how, if only known forms of matter and known forces were at work, such a large structure was formed in the time since the Big Bang . Newer technologies and continued research promise to introduce new insights into the universe.

Activity

See for yourself what a difference a 3-D map can make. You will observe models of constellations and galaxies from different vantage points to see how things look different when viewed from different locations. Materials
  • constellation and galaxy maps
  • drawing paper 18" x 24"
  • pieces of cardboard 18" x 24"
  • black paint OR construction paper
  • string
  • tagboard
  • markers
  • aluminum foil
  • scissors
    PART I
  1. Divide the class into teams of four.
  2. Have each team choose a favorite constellation or galaxy and make a paper map of it, using the acquired constellation maps as guides.
      PART II
    1. Make a three-dimensional (3-D) model of your chosen constellation or galaxy. Start by transforming the cardboard into the unknown "dark matter" of space by painting or covering it with construction paper.
    2. Determine the location on the cardboard and size of stars needed to create a 3-D model of the chosen constellation.
    3. Use foil, tag board, string, and markers to create 3-D star models. Attach hanging stars to the cardboard by using varying lengths and thicknesses of string.
    4. Suspend the completed 3-D maps from the classroom ceiling. Note: Your finished project will illustrate only an approximation of the placement of the stars. It would be impossible, using these materials, to make something to scale.

Resources

    NASA
    Education Division
    Mail Code F
    Washington, DC 20546
    (booklets: The Great Observatories for Space Astrophysics, NP-128; The
    Gamma-Ray Observatory,
    NP-124)
    Space Telescope Science Institute
    3700 San Martin Dr.
    Baltimore, MD 21218
    (301) 338-4707
    (slides, posters, videos, hands-on activities, brochures)
    Astronomical Society of the Pacific
    390 Ashton Ave.
    San Francisco, CA 94112
    (Universe in the Classroom newsletter)
    Community resources:
    Astronomy club
    University departments of physics and astronomy