[extropy-chat] SPACE: How many planets?

[Harvey Newstrom]

On Monday, March 22, 2004, at 07:33 pm, Mike Lorrey wrote:

> I don't think that point 2, though, is very accurate, though. There are
> LOTS of asteroids of significant sizes in orbits resonant with Earth or
> that cross Earth's orbit. This doesn't make Earth "not a planet".

Good point.  I tried to describe an asteroid "belt", but it is fuzzy 
how many it takes to make a belt.  You are absolutely right that there 
are many asteroids outside the asteroid belt.

> I wouldn't say that Sedna and Pluto are in similar or close orbits,
> either. Sedna is as far away from Pluto as Pluto is far away from Earth
> (and there are a lot of planets between us and Pluto, obviously), and
> Sedna is currently near its closest approach to the Sun, its orbit
> lasts 10,500 years.

I was lumping Pluto in with the Plutions, and Sedna with the Oort 
Cloud.  Both are thought to contain a lot of objects in their zones.

> I would suggest holding off making any final decisions about objects in
> the Kuiper Belt until we have identified a LOT more of them.

I think it is just a matter of time.

> Another issue is orbitally resonant objects. Negating Pluto as a planet
> because it is orbitally resonant with Neptune, a much larger object, I
> can understand, just as many asteroids and comets are orbitally
> resonant with Earth, but Pluto does not, in fact, orbit Neptune as a
> moon. The fact that they share an orbit (and even Pluto has its own
> moon) does not make Neptune "not a planet".

Yes, my definitions of orbital uniqueness does get fuzzy.  Your way of 
choosing the largest object makes sense.  But this makes Titan not a 
planet, while Mercury is a planet.  (I always thought the moon 
designation was sloppy anyway.  I think moons should be classified the 
same as planets, et. al.)

> Sedna does not fall into this category though, and it is the most
> significant object we've seen in that region to date. It does, in fact,
> fit the bill as the most significant object in its own orbital region,
> and it is round.

I am predicting thousands of Sedna-sized objects out there.  But I have 
no proof.  Yet....

--
Harvey Newstrom, CISSP, CISA, CISM, IAM, IBMCP, GSEC
Certified IS Security Pro, Certified IS Auditor, Certified InfoSec 
Manager,
NSA Certified Assessor, IBM Certified Consultant, SANS Certified GIAC
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