Click here for free access to our latest coronavirus/COVID-19 research, commentary, and news.

Support nonprofit science journalism

Science’s extensive COVID-19 coverage is free to all readers. To support our nonprofit science journalism, please make a tax-deductible gift today.

Gregarious Galaxies in the Early Universe

WASHINGTON, D.C.--The great clusters and walls of galaxies that pattern the universe may date back practically to the big bang. By searching the neighborhood of distant quasars--galaxylike objects so bright that they can be seen shining from the early days of the universe--astronomers have found that nearly every one has a fuzzy companion galaxy or two. These small gatherings in the infant universe, described last week at the meeting of the American Astronomical Society here, challenge the notion that the clumpiness of today's universe should have developed fairly recently.

A team of astronomers used the powerful 10-meter Keck telescope at Mauna Kea, Hawaii, to search for faint galaxies in the immediate surroundings of quasars at high redshifts (a measure of distance based on the degree to which their light is reddened by the expansion of the universe). If galaxies were distributed evenly in the early universe, as some theorists predicted, the quasar companions should be scarce. But in almost all of the 10 quasar fields studied so far, they found at least one companion galaxy. "This is the first clear detection of primordial, large-scale structure" in the universe at redshifts larger than 4, when the cosmos was less than a billion years old, says team leader George Djorgovski of the California Institute of Technology in Pasadena.

Theorist Neta Bahcall of Princeton University thinks that Djorgovski has found strong evidence for very early clustering. The findings imply that only scattered regions of the early universe were dense enough for galaxies to form, so the first galaxies naturally appeared in clumps. "These are very special places in the universe," says Djorgovski. "Chances are that we miss most of them when we observe random spots on the sky." Astronomers looking for action in the early universe, he says, need to follow the bright lights of quasars.