A southern slice of the universe.
(CAMBRIDGE, MA) Should anyone doubt that galaxies appear to dot the surfaces of giant bubbles, new results from a mammoth project to map the large-scale structure of the universe should lay those doubts to rest. In the March 20th Astrophysical Journal Letters, Luis Nicolaci da Costa (Brazilian National Observatory) and his colleagues show that galaxies in the southern sky array themselves into sheets and voids like those found earlier to the north.
The new map represents a southern extension to the Harvard-Smithsonian Center for Astrophysics (CfA) redshift survey, which uses the cosmological redshift to gauge the distances to galaxies as faint as magnitude 15.5 in blue light. More than 10,000 northern galaxies have been mapped already, and da Costa's group has now added 3,592 southern ones.
"We undertook the southern survey," says team member Margaret Geller (CfA), "in order to test the data from our northern map." Some researchers had worried that the huge structures discovered in the north were merely flukes in that part of the sky. Now it is clear that galaxies form bubbles and voids no matter where you look.
One of the largest structures in the northern sky, the so-called Great Wall, has a counterpart that da Costa and his coworkers dub the Southern Wall. It comprises more than a thousand galaxies, sprawls across several hundred million light-years, and apparently extends beyond the region surveyed so far. Despite years of trying, theorists still have no satisfactory explanation for how such enormous structures could have formed in only 10 to 20 billion years, the time since the Big Bang.