Star Light, Star Bright  by Micheal Schneider

"When the stars
threw down their spears
And watered heaven
with their tears
Did he smile
his work to see?"
-- from William Blake, "The Tyger"

Jeremiah Ostriker

Nickolay Gnedin



End of the Dark Ages

Evening in the country, open spaces, wide sky. The sun is sinking. A pale glow lingers overhead as darkness creeps in from the east. A gleam of light catches the corner of your eye. First star. Make a wish. The daily drama of this moment, replayed through human time, hints at a similar moment billions of years ago. Before there was a Milky Way Galaxy, solar system, or planet Earth, out of cosmic darkness came the first star in the universe.

To people such as Princeton cosmologist Jeremiah Ostriker and Nickolay Gnedin, his collaborator at the University of California, Berkeley, this moment marks a singular phase in the evolution of the cosmos. "There was a period we can characterize as the end of the dark ages," says Ostriker, "when all the activity we now take for granted started -- the first stars, the first supernova, the beginning of galaxy formation."

It's poetic justice that the first close look at this era comes from a computer called the Origin. Using NCSA's SGI CRAY Origin2000, Ostriker and Gnedin carried out a series of simulations that for the first time provide detailed understanding of this stage in the growth of the universe. "It's the first quantitative investigation," says Gnedin, "of this epoch of the Big Bang."

Unlike prior studies of this period, Ostriker and Gnedin's simulation is a fully nonlinear, 3D treatment that includes hydrodynamics, the physics that describes how matter in the early universe cools after the very hot, early moments of the Big Bang and collapses under the force of gravity into gas clumps that become the first stars. Their results provide new confirmation for one of the most well accepted versions of Big Bang theory. They also provide a host of illuminating explanations for astronomical puzzles, such as what the first galaxies look like and how elements from the upper rungs of the periodic table got scattered like dust between the galaxies.

In what corner of the cosmos did the first star twinkle? Animations from the Origin2000 computations, produced by NCSA's scientific visualization staff, allow Ostriker, Gnedin, and others to partake in a virtual replay of this moment, and it's hard not to feel a certain elation. "It's exciting to see the first stars form," says Ostriker. "They sort of blow little bubbles around themselves, where they ionize the gas and reheat it."

Reionizing the Cosmos