on Cosmic Voids
Even with more than 90 percent of its mass dark, the universe has
revealed enough secrets to permit initial efforts at mapping its
large-scale structure. Improved technologies have enabled astronomers
to detect red shifts and infer velocities and distances for many
thousands of galaxies. New research projects will plumb the secrets
of nearly one million more. And yet, we have much more to learn
from the hundreds of billions of galaxies still unexplored.
in the exploration is an ingenious method commonly used to estimate
distances to and map the locations of remote galaxies, a method
developed with help from NSF. R. Brent Tully of the University of
Hawaii and his colleague at the NSF-funded National Radio Astronomy
Observatory, J. Richard Fisher, discovered that the brighter a galaxythat
is, the larger or more massive it is, after correcting for distancethe
faster it rotates. Using this relationship, scientists can measure
the rotation speed of a galaxy. Once that is known, they know how
bright the galaxy should be. Comparing this with its apparent brightness
allows scientists to estimate the galaxy's distance. The Tully-Fisher
method, when properly calibrated using Cepheid variable stars, is
proving to be an essential tool for mapping the universe.
early 2000, researchers announced the discovery of a previously
unknown quasar that qualified as the oldest ever found-indeed, as
among the earliest structures to form in the universe. Quasars are
extremely luminous bodies that emit up to ten thousand times the
energy of the Milky Way. Eventually our maps will include everything
we know about the universe-its newly revealed planets, the inner
workings of the stars, distant nebula, and mysterious black holes.
With our map in hand and our new understanding of how the universe
began and continues to grow, we humans will have a better chance
to understand our place in the vast cosmos.