Mar 17, 17 / Ari 20, 01 19:11 UTC

The status of Pluto as a planet is still under question.  

Depending on the definition, our Solar system has either 8 or 110 planets. The question of "What is a planet ?" is still up for debate. Personally I feel that downgrading Pluto was a mistake, and agree with much of the sentiment in the following article.

Scientists make the case to restore Pluto's planet status https://phys.org/news/2017-03-scientists-case-pluto-planet-status.html

Mar 17, 17 / Ari 20, 01 19:16 UTC

Whilst I'd personally suggest Pluto is a planet, I'd not agree to there being 110 planets in this solar system.

For example, europa isn't a planet - an astronomical body closely orbiting a larger body commonly being a moon.

Mar 26, 17 / Tau 01, 01 23:02 UTC

Yeah, 110 seems a bit much, but the issue is down to pedantry it seems (from both camps), because under the current system more planets are arguably not planets.

QUOTE

Runyon and his co-authors argue for a definition of "planet" that focuses on the intrinsic qualities of the body itself, rather than external factors such as its orbit or other objects around it. In a short paragraph, they define a planet as "a sub-stellar mass body that has never undergone nuclear fusion" and that has enough gravitational heft to maintain a roughly round shape, even if it bulges at the equator because of a three-way squeeze of forces created by its gravity and the influence of both the sun and a nearby larger planet.

This definition differs from the three-element IAU definition in that it makes no reference to the celestial body's surroundings. That portion—which required that a planet and its satellites move alone through their orbit—excluded Pluto. Otherwise, Pluto fit the IAU definition: it orbits the sun and it is massive enough that the forces of gravity have made it round.

Stern has argued in the past that the IAU definition also excludes Earth, Mars, Jupiter, and Neptune, which share their orbits with asteroids.

The new geophysical definition omits stars, black holes, asteroids, and meteorites, but it includes everything else in our solar system. It would expand the number of planets from eight to approximately 110.

END QUOTE

BTW. If anyone wants a nice picture of Pluto for their desktop, there is a new posting with the complete stitched image which clearly shows the atmosphere of the "Planet" Pluto.

http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?page=1&galleryid=2&imageid=485

Mar 28, 17 / Tau 03, 01 13:34 UTC

Planets orbit suns, in addition to all their other physical qualities that Runyon and his friends state. That is something all children know: planets orbit the sun.

Mar 28, 17 / Tau 03, 01 13:40 UTC

There's lots of things that are "common knowlege" but entirely untrue, it's not a good measure.

However, I do agree that planets orbit stars, and moons orbit planets - it's not a complicated formula and seems to of worked out well so far.

  Updated  on Mar 28, 17 / Tau 03, 01 13:41 UTC, Total number of edits: 1 time
Reason: typo

Mar 28, 17 / Tau 03, 01 15:44 UTC

Comment deleted

  Updated  on Jun 15, 17 / Can 26, 01 16:02 UTC, Total number of edits: 1 time
Reason: "This user no longer wishes to be associated with a tin pot banana republic"

Mar 28, 17 / Tau 03, 01 15:59 UTC

Indeed, but as a base qualifier - amongst other properties - the condition is generally true more than it is not.

  Updated  on Mar 28, 17 / Tau 03, 01 15:59 UTC, Total number of edits: 1 time
Reason: typo

Mar 28, 17 / Tau 03, 01 16:05 UTC

Fine. Clive wants to be pedantic about it, I'll give him a definition.

Planet, as defined by Phicksur, largely stolen or paraphrased from other sources, made short and succinct:

A sub-stellar mass body that has never undergone nuclear fusion, that has enough gravitational heft to maintain a roughly round shape, and that orbits a star or star cluster.

Now, name your planets.

Mar 28, 17 / Tau 03, 01 16:58 UTC

Jim, frederick, bob, sue, james, henry, penelope, scruffles.

Mar 28, 17 / Tau 03, 01 18:46 UTC

Jim, frederick, bob, sue, james, henry, penelope, scruffles.

Do we live on planet Bob or planet Henry? I prefer Bob.

Apart from missing the clear orbital neighborhood that is pretty close to the official outline.

Yep, which is why I am trying to figure out why the hell some idiot decided that a planet has to clear its orbital neighborhood. What about moons? Asteroids? Meteors? What, they don't count because some moronic astronomer said so?

What would happen if we find a different solar system with two planets in the same orbital path, like on opposite sides of the star? What, those aren't planets because they didn't clear their orbital neighborhood?