Pluto

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Jiatao24

Is Pluto still a planet?

MartinLS

No.  This is the definition from Wikipedia---

Pluto (pronounced /ˈpluːtoʊ/ , from Latin: Plūto, Greek: Πλούτων), formally designated (134340) Pluto, is the second-largest known dwarf planet in the Solar System (after Eris) and the tenth-largest body observed directly orbiting the Sun. Originally classified as a planet, Pluto is now considered the largest member of a distinct region called the Kuiper belt.[7]

Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a fifth the mass of the Earth's moon and a third its volume. It has a highly eccentric and highly inclined orbit.

Pluto's eccentricity takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun, causing Pluto to occasionally come closer to the Sun than Neptune. Pluto and its largest moon, Charon, are often treated together as a binary system because the barycentre of their orbits does not lie within either body.[8] The International Astronomical Union (IAU) has yet to formalise a definition for binary dwarf planets, and until it passes such a ruling, Charon is classified as a moon of Pluto.[9] Pluto has two known smaller moons, Nix and Hydra, discovered in 2005.[10]

From its discovery in 1930 until 2006, Pluto was counted as the Solar System's ninth planet. In the late 20th and early 21st centuries, however, many objects similar to Pluto were discovered in the outer solar system, notably the scattered disc object Eris, which is 27% more massive than Pluto.[11] On August 24, 2006 the IAU defined the term "planet" for the first time. This definition excluded Pluto, which the IAU reclassified as a member of the new category of dwarf planets along with Eris and Ceres.[12] After the reclassification, Pluto was added to the list of minor planets and given the number 134340.[13][14] A number of scientists continue to suggest that Pluto should be reclassified as a planet.[15]

Sharukin

Pluto was a planet then a dwarf planet and now it is a Plutoid. Confused? So am I.

Ryuzaki_Lawliet

Scientics can't admit they can't really determine the right thing so they rename crap. But with pluto i can kindof understand. it's far and new discoveries are being made.

ck516

But still, the one thing it isn't is a planet!

bbrout

Let's say there is a bit of a debate going on within the IAU. If you want to call Pluto a planet, then by all means, do so. It's a free country. The IAU, on the other hands, has decided not to call it a planet. I guess there is no law against them doing so or not doing so. The best comment I have heard so far on Pluto's planetary non-designation is that we are violently apathetic to this issue. I believe that is an admirable position to take.

Elroch

I've never been one who could get passionate about what people call things. I'm more interested in what they are. Pluto has not changed in the tiniest way as a result of its reclassification.

diomed1

  MartinLS, thank you. I didn't know about Nix and Hydra. I wonder what kind of orbits they follow considering the binary nature of Pluto/Charon. They must fall pretty close to Pluto to remain stable with Charon's influence.

  Reminds me of the sheperd moons in Saturn's rings.

bbrout

Make a heck of a study for the three-body problem.

Elroch

Just thinking, it's really lucky that Pluto had not been discovered when Holtz wrote his very popular suite "The Planets", or now it would have to be renamed, "The Planets Plus One Dwarf Planet That Wandered In From The Kuiper Belt"