Among her fellow astronomers, Vera Rubin is known as an expert
observer of the night sky, one of the best. Her reputation derives from the
project she has doggedly pursued through most of her career: measuring how (1) ______
fast spiral galaxies are spinning, from their luminous cores out of the faint (2) ______
wisps of light at their fringes. Such a task may sound tedious; even her
colleagues thought so when she started the project 20 years ago. But for her (3) ______
painstaking measurements Rubin has learned something important about
galaxies: they spin so fast they have to fly apart. Since galaxies do not seem (4) ______
to be shedding stars the way like a rotating lawn sprinkler shed water; (5) ______
moreover, something must be holding the stars in. That something has to be (6) ______
gravity, no other force is powerful enough on a galactic scale. And where (7) ______
there is gravity, there is mass. Rubin realized that a huge reservoir Of extra
materials, invisible to her telescope, must be tucked away somewhere in each (8) ______
galaxy. We cannot see this matter—it is invisible to all our detectors. But
this "dark matter" seems to make up at least 90 percent of the mass of the
universe,
Large because of Rubia’s work, dark matter has become the buzzword in (9) ______
Astronomy. Her work has stirred Such ferment that observers are desperate to (10) ______
find some way of seeing dark matter and theorists are desperate to find an
explanation of what it is—swarms of unknown elementary particles, for
instance, hidden armadas of Jupiter-like planets.