287
See also: The Kuiper belt 184 ■ The Oort cloud 206 ■ Studying Pluto 314–17
THE TRIUMPH OF TECHNOLOGY
of spotting small icy objects beyond
Neptune. Americans David Jewitt
and Jane Luu were among the
astronomers who set about the
difficult task. After five years of
searching, in 1992, Jewitt and
Luu discovered an object formally
designated 1992 QB1, the first body
to be found beyond Neptune since
Pluto, and the first evidence that
the Kuiper belt was real.
Cubewanos and plutinos
More than 1,000 Kuiper Belt Objects
(KBOs) are now known and there
are probably thousands more.
They are designated as asteroids,
but unlike most asteroids, KBOs
are typically a mixture of rock
and ices. The largest are several
hundred miles across and many
of them have moons.
1992 QB1 is typical of the KBOs
in the most densely populated
middle part of the Kuiper belt, about
45 AU from the sun. These KBOs
are sometimes called “cubewanos.”
Closer in, at around 40 AU, the
gravity of Neptune has thinned
out the Kuiper belt, leaving a family
of objects (including Pluto itself)
called “plutinos,” in orbits that are
unaffected by Neptune’s gravity.
Beyond the main Kuiper belt lies
a region called the “scattered disk,”
which includes the large objects Eris
and Sedna. It is now believed thatGerard Kuiper Gerard Kuiper was born
in the Netherlands in 1905.
At a time when few other
astronomers were interested
in the planets, Kuiper, working
mostly at the University of
Chicago, made many discoveries
that changed the course of
space science: he found that the
Martian atmosphere was mostly
carbon dioxide, that Saturn’s
rings comprised billions of chunks
of ice, and that the moon was
covered in a fine rock dust. In
1949, Kuiper’s idea that the
planets were formed from
a cloud of gas and dust thatsurrounded the young sun
changed scientists’ view
of the early solar system.
In the 1960s, Kuiper
helped identify landing sites
on the moon for the Apollo
program and cataloged
several binary stars. He died
of a heart attack in 1973, at age- Since 1984, the Kuiper Prize
has been awarded annually by
the American Astronomical
Society to recognize achievement
in planetary science, a field
of astronomy in which many
consider Gerard Kuiper to
have been the pioneer.
this region is the source of short-
period comets. In 2006, Eris was
designated a dwarf planet along
with Pluto. Since then, two more
cubewanos, Makemake and
Haumea (Haumea is orbited by two
small moons), have been classed
as dwarf planets, with many more
KBOs listed as candidate dwarf
planets. Scientists believe that
these KBOs resemble the primitive
bodies that formed the planets. ■The egg-shaped dwarf planet Haumea
hangs in the sky above one of its two
moons, Namaka. Haumea, discovered
in 2004, is the third-largest dwarf planet.