Astronomers grapple with cosmic
puzzles both dark and light
By Ron Cowen
Four hundred years ago, astronomy embraced
all that was visible. For Galileo, looking through
his primitive telescope, the vistas included
jewel-like stars, mountains on the moon, moons
orbiting Jupiter and the glow of comet tails.
Today astronomy is often about what cannot
be seen. Astronomers have known for decades
that stars and galaxies are mere baubles
floating on a vast sea of dark matter. More
recently, astronomy’s roster of Darth Vaders
has expanded to include an even more mys-
terious force: dark energy, an entity that drives
the universe to accelerate its expansion just
when gravity’s tug ought to be slowing it down.
On the brighter side, astronomers are be-
ginning to learn more about the complicated
processes that formed stars and galaxies,
giving the universe its light. The Planck
mission (
SN: 4/11/09, p. 16
) will test the idea
The first stars that lit up the cosmos (white areas in this
artist’s illustration) coalesced inside halos of dark matter
(purple), according to the leading model of star formation.
Cover
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