Weighing Empty Space
Explanation:
Sometimes staring into empty space is useful.
Pictured above is a region of sky that was picked because it had,
well, nothing: no
bright stars,
no
bright galaxies, and no
picturesque nebulas.
What could not be avoided, however, were a few stars in
our own Galaxy, and
many distant galaxies strewn
across the universe.
Now the more distant galaxies have their
light slightly deflected
by the gravity of more nearby galaxies,
causing them to appear slightly
distorted.
By
analyzing these
gravitational lens distortions,
nearby mass concentrations can be found,
regardless of how bright they appear.
Using this method, astronomers can now weigh entire
clusters of galaxies
and search for large groupings of relatively
dark matter.
Circled in the lower right of the
above image is a cluster of galaxies that
was found not by its light, but by its mass.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
