At present
the Solar
System
is officially comprised of a star (theSun),
eight "planets" (Mercury,
Venus,Earth,Mars,
Jupiter,
Saturn,
Uranus
and Neptune),
five newly classified "dwarf planets" (Ceres, Pluto,Haumea,
MakemakeandEris[1] the latter
four of which are also designated as "plutoids") [2] and
numerous attendant satellites and
assorted debris such as asteroids, comets, dust and meteors.
Intelligent
life within the Solar System appears to be limited to Earth (at least
insofar as visual data of the other planets and a lack of
electromagnetic emissions is concerned), this is not to say that there
isn’t life, only that a technological civilization isn’t in evidence.
Whether there is bacteria on Mars, porpoise like creatures in the
oceans beneath a layer of ice on the Galilean moon Europaor giant
gas bags floating
in the outer layers of Jupiter’s atmosphere is yet to be determined.
The
Milky
Way galaxy is an immense area 100,000 light years in
diameter; the
Solar System lies about 28,000 light years from it's center; our Sun a
yellow star about halfway through its main-sequence (a period of
relative stability) is somewhat commonplace.
We are, however, the focal point of an expanding globe of
electromagnetic radiation that signals our presence (though if we
continue
to switch from powerful
transmitters to cable and satellites we will eventually become "radio
quiet" and difficult to detect), and we listen with giant radio
telescopes
for a reply but as yet nothing. Are we alone or
perhaps a backwater surrounded by advanced life forms
communicating with each other in ways we have yet to fathom? It is
possible that we are playing tom-toms while they are watching high
definition television.
[1] Passed August 24, 2006, by the International Astronomical Union:
The
IAU . . . resolves that planets and other bodies, except satellites, in
our
Solar System be defined into three distinct categories in the following
way:
(1) A "planet" is a celestial body that (a) is in orbit
around the Sun, (b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes a hydrostatic equilibrium
(nearly round shape) and (c) has cleared the neighborhood around its
orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit
around the Sun, (b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes a hydrostatic equilibrium
(nearly round shape), (c) has not cleared the neighborhood around its
orbit and (d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be
referred to collectively as "Small Solar System Bodies."
[2]
Formally announced June 11, 2008, by the
International Astronomical Union:
"Plutoids"
are celestial bodies in orbit around the Sun at a semi-major axis
greater than that of Neptune (trans-Neptunian)
that have
sufficient mass for their
self-gravity to overcome rigid body forces so that they assume a
hydrostatic equilibrium (nearly round shape) but have not yet
cleared
the neighborhood around their orbit. (At present only Pluto, Haumea,
Makemake and Eris fill all these requirements, Ceres does not.)
Satellites of
plutoids
are not plutoids themselves.
