Orbiter-Forum  

Go Back   Orbiter-Forum > Far Side of the Moon > Astronomy & the Night Sky
Register Blogs Orbinauts List Social Groups FAQ Projects Mark Forums Read

Astronomy & the Night Sky Astronomy news & discussions, Astrophotography, Telescopes, Star Charts, & more. Galaxies, Stars, Planets & Moons, discuss it all here!

Reply
 
Thread Tools
Old 03-08-2016, 09:11 PM   #46
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

Quote:
Originally Posted by n122vu View Post
 Endor was a forest moon.
Yavin 4, too.
orb is offline   Reply With Quote
Old 03-08-2016, 09:50 PM   #47
RisingFury
OBSP developer
 
RisingFury's Avatar
Default

Quote:
Originally Posted by TMac3000 View Post
 But "It has clouds" combined with "It orbits the Sun" is quite convincing. That wouldn't demote any of the classical planets, and also would not promote anything in the Asteroid belt or Kuiper Belt (unless Ceres or Sedna could be shown to have atmospheres).
If Pluto has clouds, other Kuiper belt objects could as well. We could again end up with many planets
RisingFury is offline   Reply With Quote
Old 03-08-2016, 10:12 PM   #48
Urwumpe
Certain Super User
 
Urwumpe's Avatar

Default

Quote:
Originally Posted by RisingFury View Post
 If Pluto has clouds, other Kuiper belt objects could as well. We could again end up with many planets
Not that easily... Most could be too cold for a permanent atmosphere. Pluto is a special case, because at least for the known segment of its orbit, it looks like the atmospheric pressure actually climbs when it should be declining.

---------- Post added at 11:12 PM ---------- Previous post was at 11:02 PM ----------

Another one arguing towards calling Pluto a planet:

https://palereddot.org/what-is-a-planet/

With a small important critical error though - Trojans are gravitationally bound to Jupiter and not invalidating the clear neighbourhood criteria for a planet.

But still not the worst argumentation because of its conclusion: Would we not call Pluto a planet, if we would discover it in another solar system?
Urwumpe is offline   Reply With Quote
Old 03-08-2016, 11:15 PM   #49
kuddel
Donator
Default

Quote:
Originally Posted by Urwumpe View Post
 Would we not call Pluto a planet, if we would discover it in another solar system?
No, we would call it an Exoplanet
kuddel is offline   Reply With Quote
Thanked by:
Old 03-09-2016, 02:36 AM   #50
Lmoy
Donator
Default

Quote:
Originally Posted by Urwumpe View Post
 Would we not call Pluto a planet, if we would discover it in another solar system?
Sure, and Titan would likely be a planet if it was orbiting all on its own, but it depends on location relative to other bodies as well as size, so saying "what if it was in a different location" doesn't work very well as an argument. Earth could just as easily be the moon of a superjupiter, and then definitely wouldn't be a planet, but it's free to dominate its orbit without a bigger planet controlling ii, which means it is a planet.
Lmoy is offline   Reply With Quote
Old 02-26-2017, 03:43 PM   #51
RGClark
Mathematician
 
RGClark's Avatar
Default

Will Pluto Get Its Planethood Back?
By Mike Wall, Space.com Senior Writer | February 22, 2017 02:00pm ET
http://www.space.com/35789-pluto-pla...efinition.html

The definition being proposed by this group of scientists including Alan Stern principal investigator of the New Horizons mission is essentially anything round that is not a star.

This definition though would include the large moons such as our own Moon, Titan, Europa, etc.

I think they would get more support if they excluded moons that were clearly in orbit around larger planetary bodies.

Bob Clark

Last edited by RGClark; 03-08-2017 at 07:24 PM.
RGClark is offline   Reply With Quote
Thanked by:
Old 02-26-2017, 08:47 PM   #52
K_Jameson
Orbinaut
 
K_Jameson's Avatar
Default

Such a definition makes sense.
After all, a star is always a star, regardless of his orbit.
The term "moon", after all, is merely an orbital indication, unrelated with the phisical characteristics of the body. So, mabye, a moon can be... a moon and a planet at the same time.
K_Jameson is offline   Reply With Quote
Thanked by:
Old 02-26-2017, 10:14 PM   #53
MikeB
Orbinaut
 
MikeB's Avatar
Default

Quote:
Originally Posted by RGClark View Post
 I think they would get more support if they excluded moons that were clearly in orbit around larger planetary bodies.
Bob Clark
Is the Moon clearly in orbit around a larger planetary body? Or is the Earth-Moon pair two planets in a nearly common orbit around the Sun? After all, the Moon is well outside the Earth's sphere-of-influence (SOI), as Orbiter constantly shows us on lunar flights.

Take a look at this diagram of a section of their trajectories: https://en.wikipedia.org/wiki/Orbit_...rajectory1.svg

Also see the Wikipedia article: https://en.wikipedia.org/wiki/Orbit_...oon_around_Sun
MikeB is offline   Reply With Quote
Old 02-27-2017, 04:22 AM   #54
boogabooga
Bug Crusher
 
boogabooga's Avatar
Default

For me, this is the essential take-away of the article:

Quote:
"This definition highlights to the general public and policymakers the many fascinating worlds in our solar system that remain unexplored and are worthy of our exploration, along with the necessary budgets," they wrote.
Emphasis mine.

What the very rational astronomy nerds (I don't mean that as an insult) at the IUA don't realize is that we are living in a hyper-political world and what you call things matter. Hype and self-promotion win the day, not honest modesty. Calling what you want a billion dollars to go visit a "planet" is better P.R. than just about anything else.

No surprise to me at all that Anal Stern and team- who rely on the good will of Congress- would be leading the charge.
boogabooga is offline   Reply With Quote
Old 02-27-2017, 06:40 PM   #55
K_Jameson
Orbinaut
 
K_Jameson's Avatar
Default

Quote:
Originally Posted by TMac3000 View Post
  But "It has clouds" combined with "It orbits the Sun" is quite convincing. That wouldn't demote any of the classical planets, and also would not promote anything in the Asteroid belt or Kuiper Belt (unless Ceres or Sedna could be shown to have atmospheres).
Seems to me that we are in search of an "ad personam" definition that is meant to promote Pluto, and only Pluto.

To me, the only threshold between a planet and a not-planet should be the mass. Or, less arbitrarily, the hydrostatic equilibrium.
Other factors (as the clouds) seems "artificial" and not scientific.

Also, the orbit should not count. If we take Titan or Ganymede or even the Moon, Pluto, Eris or Ceres... they would be planets in another place.
K_Jameson is offline   Reply With Quote
Reply

  Orbiter-Forum > Far Side of the Moon > Astronomy & the Night Sky


Thread Tools

Posting Rules
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
Forum Jump


All times are GMT. The time now is 07:15 AM.

Quick Links Need Help?


About Us | Rules & Guidelines | TOS Policy | Privacy Policy

Orbiter-Forum is hosted at Orbithangar.com
Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2007 - 2017, Orbiter-Forum.com. All rights reserved.