Definition of Planet to be Announced in September

MasaMuneCyrus writes "After over seven years of debating, the International Astronomical Union announced that it expects to announce the official definition of a planet in September. After many-a-deadlock, they handed the task of deciding exactly what a planet is to a new committee, which includes historians and educators. 'They wanted a different perspective from that of planetary scientists,' said Edward Bowell, an astronomer at Lowell Observatory who is also vice president of the IAU's Division III-Planetary Systems Sciences group. If all goes according to plan, the wording will be proposed in their 12-day General Assembly meeting in Prague."

Comments

Will they finally discount pluto?

[Shrithe]

I hope Pluto finally gets excluded from planet definition. It's too small (only twice the size as it's "moon", Charon, and a little less than a fifth as massive as Luna), it's out of the plane of the elliptic (a trait shared with objects like comets, but not any planets), and it's not even orbiting in a stable configuration with regard to Neptune (for part of it's orbit, Pluto is in fact eighth, and Neptune ninth).

Then there's the fact that it only really got counted as a planet in the first place because astronomers at the time of it's discovery were hung up on the idea of discovering a ninth planet. They thought they found a disturbance in Neptune's orbit, which they attributed to a ninth planet, but ended up being caused by the fact that they were working from bad data about Neptune's mass. Pluto's much too small to have any effect on Neptune's orbit.

This might finally put the final nail in the coffin of the idea of nine major planets in our solar system. We can only hope.

Re:Who cares?

[RsG]

I've always thought that looking for intelligent life on other planets is premature, since we haven't conclusively found intelligent life on this one yet :-P

But seriously, what difference does life make? Any planet could support life if you put it in a habitat of some sort. Even gas giants could support life if said habitats floated (and yes, that hs been proposed - human breathable air is a lifting gas when the outside pressure is high enough). If you mean indigenous life, that's another story - we're very likely alone here in our solar system, so seeking to define a livable planet when we have exactly one example is a bit premature.

If you want to find examples of life outside our solar system, good luck. The best we can do currently is look for either signs of intelligence (which is SETI's business), or else look for a planet that shows signs of an oxygen atmospherem, since that would imply biological processes. We're already doing this IIRC.

And even then we'd be unable to show that a rocky body of the right temperature didn't have life - anaeorbic (sp?) life gets along just fine and dandy without toxic oxygen fouling up their enviroment. That doesn't even get into the possibility of life forms existing with completely different chemical composition, which we can't even make an educated guess about.

We couldn't even show that there isn't intelligent life somewhere, since there is no guarantee that they'd use the same methods of communicating as we do - all we can do is hope they're trying to contant us.

"Moon system"

[vlad_petric]

The baricenter of Pluto and Charon is outside Pluto (in space). That's one reason, I guess, for scientist to also call it a "dual planet" system.

OTOH the other two moons are small enough to be called moons.

my homebrew nomenclature

[circletimessquare]

for what it's worth (not much):

planet = mostly rock/metal sphere with a significant atmosphere (what "significant" means becomes a point of contention then of course)

asteroid = solid rock/metal object that is not spherical

moon = rock/metal sphere without an atmosphere

a gas giant should be considered as something different than a planet (mostly gas, obviously spherical)... a star is simply a gas giant that has achieved thermonuclear fusion... and in between you have your brown dwarfs and other objects occuring at the end of a star's life time/ before it's lifetime/ malformed and never quite stars, etc.

and comets should also come to mean any agglomeration of ice and rock and dust that is loosely packed, not just those we see streaming towards the sun on a regular basis... as we explore the oort cloud, we'll find plenty of these "dormant" comets

and most importantly: all of these objects should be defined independently of what they orbit

so mercury isn't a planet, it's a moon of the sun

likewise, pluto is a moon of the sun

and ceres and vesta are moons of the sun (small perfectly spherical "asteroids")

titan isn't a moon, it's a planet of saturn (it has a significant atmosphere)

the most important thing i think, no matter what nomenclature is agreed upon, is that as we discover weirder extrasolar objects out there, the "what it orbits" part of an object's identity should come to mean something totally different than "what it's made of"

and size should never have meaning

then of course, we have to come to grips with direction of orbit, orbits outside the elliptical, orbits with bizarre shapes, binary/ tertiary objects, binary/ tertiary/ quartanery star systems, etc.