The Astronomy Book

275

See also: Spiral galaxies 156–61 ■ Beyond the Milky Way 172–77 ■ Cosmic inflation 272–73 ■
A digital view of the skies 296

THE TRIUMPH OF TECHNOLOGY

Before Huchra began his survey,
it was known that galaxies
existed in clusters. For example,
the Milky Way is one of at least
54 galaxies in a cluster called the
Local Group, which is about 10
million light-years wide. It was
assumed that clusters were evenly
spread. However, by 1980, Huchra
had shown through his redshift
survey that dozens of clusters
form superclusters hundreds of
millions of light-years wide.
The Local Group is part of the
Laniakea Supercluster, which
contains 100,000 other galaxies.

Walls of galaxies
In 1985, Geller began the CfA2
Redshift Survey, taking 10 years
to map 15,000 galaxies. Her survey
confirmed that superclusters were
themselves arranged in sheets and

walls enclosing vast voids, like the

surface film of a bubble. She found

the first “great wall” of galactic

superclusters in 1989. The exact

size of CfA2 Great Wall is still

unclear, but it is estimated at 700

million light-years long, 250 million

wide, and 16 million thick. It was

the first of several supersized

structures now known.

The size of the voids puzzled

astronomers. They were too large

to have been emptied completely

by the gravitational collapse of

material that formed the stars and

galaxies, which meant that they

must have been empty since

the beginning of the universe.

Cosmologists theorize that the

large-scale order of superclusters

and voids is the legacy of quantum

fluctuations during the inflationary

epoch of the universe. Quantum

fluctuations are fleeting changes

in the amount of energy at points

in space. These small but highly

significant irregularities were

locked into the fabric of the

universe in the first fraction

of a second of its existence, and

remain today. They are now the

vast areas of void permeated by

a tangled pattern of matter. ■

Galaxies form clusters and superclusters that fill

narrow bands of space around vast empty voids.

These voids are too large ever to have contained matter.

They must have been present in the very early universe.

This computer simulation of a
portion of the universe shows the
distribution of 10,000 galaxies, which
cluster in long filaments and “walls,”
in between vast empty voids.