of the universe. Guth asserted that, contrary to theo-
retical expectations, the universe is flat, homoge-
nous, and uniform in all directions. Soon after its or-
igin in the big bang, Guth argued, the universe must
have undergone a phase transition—a period of
rapid expansion during which the strong nuclear
force was disassociated from the electromagnetic
and weak forces. This “inflationary model” quickly
became a fundamental part of cosmological theory.
In 1987, Eugene Parker explained how the Sun’s
corona is heated by energy released in “micro flares”
as the solar magnetic field continuously oscillates. A
year later, Walter Johnson and Joseph Hollweg pub-
lished a model of hot, proton-producing coronal
holes that accounted for the fast solar wind. Also in
1988, Martin Duncan, Thomas Quinn, and Scott
Tremaine solved a puzzle about the solar system’s
short-period comets by demonstrating that most of
them originate in the Kuiper Belt beyond Neptune,
instead of in the more distant Oort Cloud, as had
previously been believed.
Several discoveries were made in deep space that
were important to theories about the universe’s
structure. In 1981, a giant void—100 million light-
years of empty space—was found in the constel-
lation Boötes, and in 1987 several American scien-
tists accumulated evidence that a
large number of galaxies within
200 million light-years of the
Milky Way were being drawn in
the direction of the constellations
of Hydra and Centaurus toward a
point that they called the Great
Attractor. In 1989, Margaret Gel-
ler and John Huchra mapped a
similarly immense structural fea-
ture, the Great Wall (later the
CfA2 Great Wall), a plane of gal-
axies occupying a space 200 mil-
lion by 500 million by 15 million
light-years in volume. These bod-
ies called into question existing
cosmological theories, which were
unable to account for the forma-
tion of such large superstruc-
tures.
In 1982, astronomers first de-
tected the Sunyaev-Zel’dovich ef-
fect, a peculiarity in the cosmic
microwave background radiation
that had been predicted in 1969. In 1987, Canadian
astronomer Ian Shelton discovered a supernova,
dubbed SN 1987a, in the Large Magellanic Cloud,
adjacent to the Milky Way.Space Probes and Observatories Voyager 1 passed
by Saturn in 1980, detecting three new moons and
finding new complexities in the planet’s rings. Voy-
ager 2 flew by the next year, probing Saturn’s atmo-
spheric temperature and density, and then went on
to Uranus in 1986 and Neptune in 1989, discovering
or confirming the existence of ten moons and seven
moons, respectively. Voyager 2 also revealed a mag-
netic field around Uranus and discovered the Great
Dark Spot, a hole in Neptune’s cloud cover.
Earth-orbiting observational satellites brought
increased variety and power to astronomers. The So-
lar Maximum Mission, launched in 1980, proved
that the Sun’s energy output varies. The Infrared
Astronomical Satellite (IRAS), launched in 1983,
spent ten months surveying intra- and extra-galactic
infrared sources, produced the first images of the
Milky Way’s core, and discovered five new comets in
the solar system. SPARTAN 1 (1985) and instru-
ments aboard Spacelab 1 (1983) and Spacelab 2
(1985), all deployed from space shuttles, gatheredThe Eighties in America Astronomy 77
A model of the Voyager spacecraft’s trajectory through the solar system. Voyager 1 and Voy-
ager 2 contributed greatly to astronomers’ knowledge of the solar system in the 1980’s.
(NASA CORE/Lorain County JVS)