August 22, 2010
Double Planet and the Planetary Archetype
Then something deep within us is awakened when we see our own little home from a different viewpoint.
Take a look at the latest snapshot of our home planet--the loopback address--from another set of eyes called MESSENGER, gazing back at the Earth from within the orbit of Venus. Looking like a double star, some people simply called those two bright lights as a "Double Planet", seemingly unwary of the ongoing debate about what a planet really means.
For the few, the words just naturally comes out upon seeing Earth and it's moon in a different light. When viewed from way out there, the scene tells the mind that the smaller piece of sphere is a member of the archetypal “Planet”.
But most people delve into the technical side of thinking, getting into the nitty-gritty details of defining "planet" based on one humdrum star system alone--ours.
We’ve recently heard that the moon has been called as a "Satellite Planet". But what makes a "planet" a planet? Do we really need to see things from another viewpoint before we can call other objects as planets?
My opinion is that many objects in our solar system are planets. Yes, I mean those round dwarf planets that many folks refuse to consider planets, despite calling them "Dwarf Planets".
Through the years, as I tracked the new discoveries in exoplanets, i've realized that the current definition of a planet--that definition which was voted upon--is rigidly based on our solar system alone.
Indeed, there are many exoplanets that would not be planets at all if we applied our heliocentric definition of “planet” unto them. For example, there are exoplanets with highly elliptical orbits that do not lie within the plane of their system. And then there are those that share the same orbital zone with other planets via resonant orbits, and others with retrograde orbits, and so on, ad inifintum, ad weirdum.
With all the weird new discoveries of other planetary systems that challenge our limited notions of a planet, I am led to conclude that the greatest factor of what a planet is boils down to the simple quality of being round. In scientific terms, its the hydrostatic equilibrium, the balance between gravity and pressure that molds lumps of matter into a spherical shape.
To me, that property of roundedness is the Archetype that makes an astronomical body (that orbits a star) a true planet. Round is simple, round is sublime.
Often, when I look at the moon, I see a planet. And it’s good to see it that way from a different vantage point as well. And when this satellite planet is seen together with the Earth, what we're truly seeing is a double planet.
MESSENGER: A snapshot of home http://www.planetary.org/blog/article/00002626
A 'Double Planet Seen from Mercury http://news.discovery.com/space/a-double-planet-seen-from-mercury.html