Space Station Info >> Regions Where Comets
Regions Where Comets Are Found
Comets are found in two main
regions of the cosmos: the Kuiper belt and the
Oort cloud. Short-period comets -- comets that
frequently return to the solar system -- probably
originate from an area called the Kuiper belt.
This belt is located within the solar system's
ecliptic plane, beyond the orbit of Neptune. Astronomers
found the first object in the Kuiper belt in 1992.
Since that discovery many objects have been discovered
within that region. These objects are usually
small compared with planets. Their size ranges
from 10 to 100 kilometers in diameter. Earth's
diameter, for example, is 14,000 kilometers.
The Hubble Space Telescope may have detected
a population of small comets dwelling in this
region in space. Based upon the Hubble observations,
astronomers estimate that this belt contains
at least 200 million comets, which are thought
to have remained essentially unchanged since
the birth of the solar system 4.5 billion
Long-period comets are thought
to emanate from a vast, spherical cloud of
frozen bodies called the Oort cloud, named
for the Dutch astronomer Jan Hendrik Oort.
This cloud of comets, which also orbits the
Sun, resides in the farthest region of the
solar system, beyond Neptune and Pluto.
The Oort cloud objects are made
up of matter such as frozen ammonia (), methane
(), cyanogen (), water ice (), and rock. Infrequently,
a gravitational disturbance caused by a passing
star or an interstellar cloud causes one of these
bodies in the Oort cloud to begin a journey toward
the inner solar system, where it makes a transient
rendezvous with our Sun.