Hypothesized by Estonian astronomer Ernst
It postulated that long
comets originated in an orbiting
cloud at the outermost edge of the
Orbits of comets are unstable.
There are two main classes of comets:
Short period comets (ecliptic comets)
Long period comets (isotropic comets)
There is a peak in numbe
rs of isotropic
comets in the
Thought to occupy a vast space from
somewhere between 2,000 and 5,000 AU
The region can be divided into a spherical
cloud and a doughnut shaped
The outer cloud of the
is weakly bound
to the sun and supplies the long
comets to Neptune.
Contains several trillion objects larger than 1
The inner cloud of the
is know as the
Named after J.G. Hills who proposed its
existence in 1981.
Models predict that it should
have tens or
hundreds of times as many c
omet nuclei as
the outer halo.
The mass of the
d is not known.
The vast majority of the
cloud is made
up of various ices such as
ethane, carbon monoxide
cloud and Jupiter could have both
originated from a
Thought to be a remnant of the original
protoplanetary disc that formed around the
sun 4.6 billion years ago.
Early stars played a role in the cloud’s
The evolution of the cl
oud started from the
beginning of the solar
system and peaked
800 million years ago.
Most comets are believed to reach their
current position from the Milky Way.
Galactic tide bends and distorts orbits of
bodies in the outer solar system.
The point where gravity concedes is called
the tidal truncation radius.
Richard A. Miller postulated that a red dwarf
star or a gaseous giant planet is in orbit
Supposedly passes through the cloud every
26 million years.
Upon passing it bombards
the solar system with
." The Nine Planets Solar System Tour.
Web. 15 Apr. 2011. <http://
Cloud & Sol B?"
. Web. 15 Apr. 2011.
Cloud." Views of the Solar System. Web. 15 Apr. 2011.
Cloud." Wikipedia, the Free Encyclopedia. Web. 15 Apr. 2011.
Cloud." Solar System Exploration.
Web. 15 Apr. 2011.
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