Why Pluto Isn't a Planet

thought that Pluto is not even considered its own planet, even in the dwarf category. I am under the impression that Pluto and its counterpart, Chiron, rotate around a shared center of gravity, thus making it a binary system. Why am I thinking that Pluto-Chiron is classified by the IAU as a “Double Dwarf Planet?”

As an exoplanet passes in front of its star as viewed from Earth, a very slight dip in starlight brightness is detected. Observatories such as NASA's Kepler space telescope use this "transit method" to great effect, constantly detecting new worlds.

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Carla Queen Aug 23, 2017 Actually, it's because there are so many other larger things out there that has been discovered after Pluto. If you start calling every dwarf planet a planet, the term planet would loose it's value. In addition, Pluto was just the first one spotted in the Kuiper Belt years ago, since then more have been discovered. It's a matter of knowledge and information, that we attain little by little, therefore revisions have to be made in order to maintain the new information that is discovered. Reply cancel

Astronomers estimate that there are at least 70,000 icy objects, with the same composition as Pluto, that measure 100 km across or more in the Kuiper Belt. And according to the new rules, Pluto is not a planet. It’s just another Kuiper Belt object.

It’s not impossible to imagine a future, though, where astronomers discover a large enough object in the distant Solar System that could qualify for planethood status. Then our Solar System would have 9 planets again.

Pluto follows the first two rules: It is round, and it orbits the sun. It does not, however, follow the third rule. It has not yet cleared the neighborhood of its orbit in space. Because it does not follow this rule, Pluto is no longer considered a planet.

The smart way to deal with the discovery of these new round KBOs is to keep the term “planet” as a broad category and then establish multiple subcategories, such as terrestrial planets, gas giants, ice giants, and ice dwarfs. Moons of planets that have achieved hydrostatic equilibrium could be considered secondary planets since they revolve around other planets rather than around stars. If this leads to over 100 objects falling into the broad category of planets, so be it.

Wonderopolis Dec 8, 2014 Thanks for your comment, Matthew. Pluto is smaller than regular planets, but it is big enough to be a dwarf planet. In fact, dwarf planets are typically smaller than the planet Mercury. The main distinction between a dwarf planet and a planet is that planets have cleared the path around the sun while dwarf planets tend to orbit in zones of similar objects that can cross their path around the sun, such as the asteroid and Kuiper belts. Thanks for Wondering with us! Reply cancel

Tombaugh's task was to systematically image the night sky in pairs of photographs, then examine each pair and determine whether any objects had shifted position. Using a blink comparator, he rapidly shifted back and forth between views of each of the plates to create the illusion of movement of any objects that had changed position or appearance between photographs. On February 18, 1930, after nearly a year of searching, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and 29. A lesser-quality photograph taken on January 21 helped confirm the movement.[19] After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930.[15]

This is quite a nice little news story in its own right, and covered by my Discovery News colleague Irene Klotz (see the July 20 article: "Hubble Discovers New Pluto Moon"). However, what I hadn't anticipated was a deluge of messages asking me if this means Pluto is now a planet again.

Pluto meets only two of these criteria, losing out on the third. In all the billions of years it has lived there, it has not managed to clear its neighborhood. You may wonder what that means, “not clearing its neighboring region of other objects?” Sounds like a minesweeper in space! This means that the planet has become gravitationally dominant -- there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence, in its vicinity in space.

M Jan 24, 2015 Is there anyway of choosing the right definition for Pluto in this article. It says it is a dog from Disney, but if students are reading this it would be nice for them to know the definition that relates to the article. Reply cancel

We were lost. None of us knew where we were. Then Harry starts feeling around on all the trees, and he says, "I got it! We're on Pluto." I say, "Harry, how can ya tell?" And he says, "From the bark, you dummies. From the bark!"

Pluto's visual apparent magnitude averages 15.1, brightening to 13.65 at perihelion.[1] To see it, a telescope is required; around 30 cm (12 in) aperture being desirable.[153] It looks star-like and without a visible disk even in large telescopes, because its angular diameter is only 0.11".

Also, for those of you who say that the third part where Pluto “falls down” (which I don’t agree with), I think “clear the neighborhood” means have a good orbit, like all the other eight planets. Even so, Pluto shouldn’t be turned off from a slip like that without evidence.

IntroductionThe Latest: Pluto—which is smaller than Earth’s Moon—has a heart-shaped glacier that’s the size of Texas and Oklahoma. This fascinating world has blue skies, spinning moons, mountains as high as the Rockies, and it snows—but the snow is red. These are details we didn't know before NASA's New Horizons spacecraft flew past in July 2015.

 

The only wonder I have concerning this new discovery that Pluto is not a planet is that new science is proving old science wrong. For a long time, we have known the solar system as the sun and its nine planets. We knew Pluto as a planet and so at school formulated the analogue that Mother Veronica Employs Many Junior Servants Under No Pay. Pay here represented Pluto.

Suffice to say is that teachers have taught a lie this long. It is shameful.

 

Pluto should be a planet because it was a planet until some guy wanted to make it into the history books by classifying it as a dwarf planet