Is Pluto Really a Planet?

[zavvy]

<b>Is Pluto Really a Planet?</b><br /><br />LINK<br /><br />Pluto was an accidental find by Clyde Tombaugh as he looked for the next mysterious Planet X. In the early 1900's, it was thought that a very large planet existed beyond Neptune, which would explain Neptune's unexpected deviations of motion. (This is actually how Neptune was found in the first place, using erratic motions from Uranus.) Tombaugh found Pluto and quickly deemed it a planet. Unfortunately, Pluto is too small to have been the cause of Neptune's behaviour. In fact, it turns out that Neptune's behaviour was the result of miscalculations on the part of the scientists. Pluto was just a lucky find by a determined man. <br /><br />Pluto's status as a planet remained set until David Jewitt and J. Luu discovered an object way out in space past Neptune. This object, QB1, was the first of over a hundred objects found that are now called the Kuiper Belt. These objects are very similar to Pluto in composition and orbit. Pluto's orbit is highly unusual for a planet; it is the only planet that crosses orbits with another planet. Once every 248 years, Pluto crosses the orbit of Neptune, becoming the 8th planet out, rather than the 9th. The size of Pluto also makes it "less than a planet". In fact, it is smaller than seven of the moons in our solar system. The only difference between Pluto and other members of the Kuiper Belt is its reflectivity. <br /><br />Scientists today consider Pluto to be just another object in the Kuiper Belt, though it notably is the largest object there. However, future discoveries may find Kuiper Belt objects (KBO's) that are larger than Pluto. Should those be classified as planets? Or is Pluto's time as our 9th planet coming to an end? We all grew up learning about the 9 planets. Will the public accept only 8? This almost happened years ago, and it became a media circus. The public loves tiny Pluto. The debate cont

 

[alokmohan]

Pluto is called plane simply by convention.There are plenty of kbo and If pluto is planet ,they are planet.No doubt Tombaughs discovery was unfortunate coincidece of Lowells data.But there matter stands.

 

[CalliArcale]

Interesting random factoid about planet discoveries:<br /><br />Neptune was officially discovered in 1846 based on calculations of the then-unexplained deviations in the orbit of Uranus. But that wasn't the first time it was observed. Through pure chance, Galileo Galilei observed Neptune in 1613 while observing Jupiter. He noted it, believing it to be a star too faint to be seen without a telescope. On two successive nights, he did notice that it was moving ever so slightly against the backdrop of stars. But he never saw it again; cloudy skies preventing viewing it prior to his first observation fo Neptune, and after that it had moved out of his telescope's field of view and he never found it again. Had he seen it again, he might have gone so far as to declare that he had discovered a new planet orbiting the Sun, and who knows how the Church would've reacted to <i>that</i>. <img src="/images/icons/tongue.gif" /><br /><br />Another interesting random factoid about planet discoveries:<br /><br />Pluto was <i>not</i> the ninth body to be discovered orbiting the Sun, nor was it the first body whose planetary status has been debated. In 1801, Giuseppe Piazzi discovered the asteroid 1 Ceres, initially believing it to be a comet. When its orbit was computed and found to lie between Mars and Jupiter, the astronomer Johann Elert Bode was pleased because he felt that there ought to be another planet between Mars and Jupiter. So Ceres was the new planet. But when Herschell trained his big telescope on it, it was too small to show a disk, so he called it a "star-like" object -- an asteroid. <img src="/images/icons/wink.gif" /> The debate continued for years, but a criterion had been established: an object has to show a disk in order to be called a planet and not a comet or asteroid. This became significant when Pluto was discovered and Lovell was able to show that it had a disk. Interestingly, advances in optics have allowed astronomers to directly image 1 Ceres, not only <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[drwayne]

Neptune's eventual "discovery" is an interesting story in itself, tied up in rivalry between the French and the English, with both fellows assuming Bodes Law and basically lucking into it.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[slayera]

What do you mean by disk? I think I know what you mean but I would like an explanation please. thx you ahead of time! <img src="/images/icons/smile.gif" />

 

[CalliArcale]

A sphere viewed from the side will look like a disk if you can't see enough detail or shading or contrast to make it look spherical -- if you have enough resolution, that is. Stars always look like points (except with really powerful telescopes; Hubble, for instance, can directly image the disk of the super red giant Betelgeuse). Planets, however, are near enough to show disks, because they cover (or <i>subtend</i>) a larger portion of the sky. Mars looks like a point to the naked eye, but with even a modest backyard telescope you can see its disk. The same is true of Mercury and Venus, though those can also show crescents. Jupiter shows a disk; Saturn shows a slightly squashed disk with its glorious rings, and if you have a sufficiently powerful telescope and nice, dark skies, even Uranus and Neptune will show disks.<br /><br />So that used to be the test of whether or not something was big enough to be a planet. It had to move (ruling out it being a star) and it had to show a disk. Nowdays, of course, telescopes are a lot more powerful. With the right instrument, you can even see Charon's disk. So the test isn't as useful as it once was, because it means that the definition of a planet hinges not on the nature of the object, but on Mankind's technological capabilities. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[zavvy]

You should read what Pluto has to say about all this... <br /><br />http://www.brunching.com/conversationpluto.html<br /><br />http://www.brunching.com/morepluto.html

 

[CalliArcale]

It's not a criterion anymore, kraken, and I'm not sure it was ever really formal. Heck, I don't think there's a formal criterion *now*.<br /><br />I read a book explaining how Lowell proved that Pluto had a disk. I don't recall exactly what it was, though. It wasn't a direct-imaging technique. It probably would've worked on Ceres too, had anyone bothered to try. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

The Brunching Shuttlecocks! I love that website! Sadly, it has somehow gotten into my company's "naughty filter" and so I can't visit it anymore. And I believe they stopped adding to the site a while ago. But there's some absolutely hilarious stuff there. I strongly recommend people visit zavvy's links! <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[zavvy]

<font color="yellow">Sadly, it has somehow gotten into my company's "naughty filter" and so I can't visit it anymore.</font><br /><br />What a shame. I wonder why they did that?<br /><br />It really is a cracking site! <img src="/images/icons/wink.gif" />

 

[CalliArcale]

(Wandering briefly offtopic....)<br /><br />I think it's the string "****", even though it's used in the context of a shuttlecock, which is just the thing you hit over the net in badminton and not naughty at all. Curiously, the Star Tribune's coverage of the comic strip Baby Blues is also blocked -- but not any other Star Tribune stuff. It's really not naughty at all. But I can only have them unblock it if I can show a valid business reason for visiting the site, and I don't think I can manage that for the Brunching Shuttlecocks. <img src="/images/icons/wink.gif" /><br /><br />I just hope they don't ever block Uplink! <img src="/images/icons/shocked.gif" /><br /><br />(I can come up with a valid business reason for visiting SPACE.com in general; I'm in the space business, and the company wants us to keep up with the latest industry news. But not the message board, unfortunately.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[odysseus145]

<blockquote><font class="small">In reply to:</font><hr /><p>Plutois not now the outermost planet. It's Neptune.<p><hr /></p></p></blockquote><br />Actually Pluto became the outermost planet in 1999. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

Yep, the period where Pluto was incide the orbit of Neptune ended. Too bad, it was one of those weird trivia things while it lasted.<br /><br />A wonderful Astronomy professor at Vassar, Henry Albers, made me read a fascinating book that went into the Adams/Le Verrier story of Neptune. Also made me read a book about Clyde Tombaugh...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>