Astronomers using NASA's FUSE satellite have seen in unprecedented detail the gossamer web of primordial helium that permeates space. A remnant of the big bang, the helium provides key insights into the structure of the early universe. "Visible galaxies are only the peaks in the structure of the early universe," notes team member Gerard Kriss of the Space Telescope Science Institute. "The FUSE observations of ionized helium show us the details of the hills and valleys between the mountaintops." The findings are described in the current issue of the journal Science.
Training FUSE on a faraway beacon¿a quasar located some 10 billion light-years away¿the effects of helium on the light as it traveled through helium-containing intergalactic clouds were recorded. These observations, along with complementary ones made using the Hubble Space Telescope, traced the transformation of the helium from its opaque beginnings to its transparent end.
The new findings fit well with earlier indications that the early universe was reenergized by radiation unleashed by black holes and vigorous star formation. "This is a very exciting discovery," says George Sonneborn of the NASA Goddard Space Flight Center. "The search for the spectral signatures off a forest of ionized helium gas in the early universe was one of the major objectives of the FUSE mission, and it has been fulfilled spectacularly."