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PLUTO
Feb 6, 2017 15:11:53 GMT -6
Post by auntym on Feb 6, 2017 15:11:53 GMT -6
IS PLUTO A PLANET?
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PLUTO
May 10, 2017 13:49:45 GMT -6
lois likes this
Post by auntym on May 10, 2017 13:49:45 GMT -6
astronomy.com/news/2017/02/will-pluto-be-a-planet-again WILL PLUTO BE A PLANET AGAIN? This group wants Pluto to be a planet again — and bring hundreds of objects along with it Alan Stern, principal investigator of the New Horizons mission, is ready to make Pluto a planet again ... along with Ganymede and hundreds of other objects.By John Wenz / astronomy.com/authors/john-wenz Published: Tuesday, February 21, 2017 Earth, say hello to what could be your scads of new planetary siblings. Antonio Ciccolella In 2006, science text books were changed and the hearts of millions broken when the International Astronomical Union decided to give Pluto a new classification: dwarf planet. The logic was to make it fit more with a group of new large objects discovered in the outer solar system, one of which (Eris) is nearly the same size as Pluto. That didn't prevent outcry. Indeed, when I attended the New Horizons flyby in 2015, Dava Sobel revealed how the vote might have gone: Pluto and Charon would have been regarded as a double planet, Eris would become a full planet, and Ceres would regain its planetary status. Ceres, from its discovery in 1801 to about the 1850s, was regarded as a planet, as were Vesta, Pallas, and a handful of the other asteroids. As more objects accumulated in that region of the solar system, these small bodies were relegated to minor planet status. Much the same thing happened with Pluto and the Kuiper Belt with each passing discovery. So what did the IAU declare a planet? It had to orbit the Sun (excluding moons), be in a roughly spherical shape (excluding asteroids), and clear its field of debris (excluding the dwarf planets). Had Pluto stayed a planet, and the other large Kuiper Belt Objects come with it, we might have hundreds of planets. To be a dwarf planet, the first two conditions had to be met but the object has to have "failed" at the third. Mike "Pluto killer" Brown currently lists 10 objects as dwarf planets in name or deed, another 20 as more-than-likely, and a total of 148 objects as likely to satisfy the conditions of a dwarf planet. But Alan Stern, principal investigator of the New Horizons mission, says there's a better way. In a paper put forth by Stern and others, the definition would be quite simple: "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters." Breaking that down: to be a planet, you have to be large, round, and not a star. As long as a world is rounded out by its own gravity, that makes it a planet. Which means that in this scenario, the Moon is now a planet. Tiny Enceladus and titanic Titan are both now planets. Pluto is a planet again, but so is Charon. Ceres gains its status back, though most other asteroids do not. It should be explicitly noted, as not to cause undue headaches: Pluto is not a planet again. This is simply a proposal for something to be considered. The IAU would have to accept the definition, which is definitely not a given. (I will, in the meantime, maintain my planetary-status-agnostic stance.) I asked Dr. Stern a few questions to figure out what his proposition entailed, and how a moon might become a planet. It may not gain traction, but it does underscore a good point: there's a lot more to the geology of the solar system than just the currently accepted pantheon of planets. CONTINUE READING: astronomy.com/news/2017/02/will-pluto-be-a-planet-again
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PLUTO
May 11, 2017 0:51:12 GMT -6
Post by Deleted on May 11, 2017 0:51:12 GMT -6
Well having pluto demoted messes up astrology I think. I think if I had a favorite out there it's phobos..that one attracts me..
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PLUTO
Jul 15, 2017 9:39:18 GMT -6
lois likes this
Post by swamprat on Jul 15, 2017 9:39:18 GMT -6
Question: How can Pluto have "moons" if it is not a "planet"? Just askin'.....
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PLUTO
May 12, 2018 15:14:22 GMT -6
Post by auntym on May 12, 2018 15:14:22 GMT -6
www.space.com/40550-pluto-planet-debate-flares-up-again.html?utm_source=twitter&utm_medium=social Welcome Back, Pluto? Planethood Debate ReignitesBy Mike Wall, Space.com Senior Writer / May 11, 2018 NASA's New Horizons spacecraft captured this image of Pluto during the probe's flyby of the dwarf planet in July 2015. Credit: NASA/JHUAPL/SwRIThe long-simmering argument about Pluto's planethood has just flared up again. For more than 75 years after its 1930 discovery, Pluto was regarded as our solar system's ninth planet — a distant and frigid oddball, to be sure, but a member of Earth's immediate family nonetheless. Then, in 2006, the International Astronomical Union (IAU) reclassified Pluto as a "dwarf planet," a newly created category that the organization explicitly stressed made Pluto distinct from the eight "true" planets. A true planet, according to the IAU's newly devised definition, must meet three criteria: It must circle the sun and no other object (so, moons are out); it must be big enough to be rounded into a sphere or spheroid by its own gravity, but not so large that its innards host the fusion reactions that power stars; and it must have "cleared its neighborhood" of other orbiting bodies. [Photos of Pluto and Its Moons] Pluto failed at this last hurdle, because its neighborhood — the ring of icy bodies beyond Neptune known as the Kuiper Belt — is far from cleared. Many scientists and Plutophilic members of the public objected strongly to the IAU's decision, on various grounds. For starters, some folks pointed out, the new planet definition rules out anything not orbiting the sun — meaning that the hundreds of billions of exoplanets in our Milky Way galaxy aren't planets at all, at least according to the IAU. And the "clear your neighborhood" requirement seemed ridiculous to many researchers, including Alan Stern, the principal investigator of NASA's New Horizons mission, which famously flew by Pluto in July 2015. Stern has been a vocal proponent of Pluto's planethood and has argued that the IAU's decision stemmed at least partly from a very nonscientific desire to keep the solar system's planetary stable down to a "manageable" number. Which brings us to the most recent flare-up. Stern and planetary scientist David Grinspoon have just published a book about the Pluto flyby, called "Chasing New Horizons: Inside the Epic First Mission to Pluto" (Picador, 2018). On Monday (May 7), The Washington Post published a "Perspectives" piece the two scientists wrote titled, "Yes, Pluto Is a Planet." In the piece, Grinspoon and Stern took aim at the IAU's "hastily drawn" and "flawed" planet definition, reserving special ire for the "clearing your neighborhood" requirement. "This criterion is imprecise and leaves many borderline cases, but what's worse is that they chose a definition that discounts the actual physical properties of a potential planet, electing instead to define 'planet' in terms of the other objects that are — or are not — orbiting nearby," the scientists wrote. "This leads to many bizarre and absurd conclusions. For example, it would mean that Earth was not a planet for its first 500 million years of history, because it orbited among a swarm of debris until that time, and also that if you took Earth today and moved it somewhere else, say out to the asteroid belt, it would cease being a planet." [Destination Pluto: NASA's New Horizons Mission in Pictures] The duo pushed instead for a much simpler "geophysical planet definition," which was presented last spring at a planetary science conference in Texas. And this definition is indeed simple; boiled down, it holds that planets are "round objects in space that are smaller than stars." Under this definition, Pluto and other dwarf planets, such as Ceres and Eris, are considered planets, as are large moons like Jupiter's Europa, Ganymede, Io and Callisto and Saturn's huge satellite Titan (as well as Earth's own moon). Indeed, the solar system's planet count would easily top 100 if everyone agreed to use the geophysical definition. But getting such widespread agreement about this, and about Pluto's "official" classification, will be a hard row to hoe. For example, astrophysicist and author Ethan Siegel argued in a piece for Forbes on Tuesday (May 8) that a cosmic object's environmental context is important to understanding the object's nature. "The simple fact is that Pluto was misclassified when it was first discovered; it was never on the same footing as the other eight worlds. The 2006 move by the IAU was an incomplete attempt to repair that mistake," Siegel wrote. The geophysical definition, he added, "is a step in the opposite direction: It's a step towards making a larger, more confusing mistake that will render a definition meaningless to the majority of people who use it." And then there's the pithy take by California Institute of Technology astronomer Mike Brown, whose discovery of outer-solar-system objects helped spark the rethink of Pluto's place in the solar system. "So, hey, Pluto is still not a planet. Actually, never was. We just misunderstood it for 50 years. Now, we know better. Nostalgia for Pluto is really not a very good planet argument, but that's basically all there is. Now, let's get on with reality," Brown wrote via Twitter, where his handle is @plutokiller. Brown also wrote a book, titled "How I Killed Pluto and Why It Had It Coming" (Spiegel & Grau, 2010), so his feelings on the topic are pretty well-known. Will the geophysical planet definition catch on? Will the IAU welcome Pluto back into the "true planet" fold, along with Ceres, Europa, Titan, Earth's moon and many other objects? Who knows? But it seems clear that people will be fighting about this stuff for a long time to come. www.space.com/40550-pluto-planet-debate-flares-up-again.html?utm_source=twitter&utm_medium=social
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PLUTO
Sept 7, 2018 12:46:17 GMT -6
Post by auntym on Sept 7, 2018 12:46:17 GMT -6
dailygalaxy.com/2018/09/new-rule-pluto-is-a-planet-its-more-dynamic-and-alive-than-mars/ Reboot? Pluto is a Planet –“It’s More Dynamic and Alive than Mars”Posted on Sep 7, 2018 “It’s more dynamic and alive than Mars,” says UCF planetary scientist Philip Metzger. “The only planet that has more complex geology is the Earth.” The reason Pluto lost its planet status is not valid, according to new research from the University of Central Florida in Orlando. In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to “clear” its orbit, or in other words, be the largest gravitational force in its orbit. Since Neptune’s gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status. However, in a new study published online Wednesday in the journal Icarus, UCF planetary scientist Philip Metzger, who is with the university’s Florida Space Institute, reported that this standard for classifying planets is not supported in the research literature. Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication — from 1802 — that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning. He said moons such as Saturn’s Titan and Jupiter’s Europa have been routinely called planets by planetary scientists since the time of Galileo. “The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research,” Metzger said. “And it would leave out the second-most complex, interesting planet in our solar system.” “We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it’s functionally useful,” he said. “It’s a sloppy definition,” Metzger said of the IAU’s definition. “They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.” The planetary scientist said that the literature review showed that the real division between planets and other celestial bodies, such as asteroids, occurred in the early 1950s when Gerard Kuiper published a paper that made the distinction based on how they were formed. However, even this reason is no longer considered a factor that determines if a celestial body is a planet, Metzger said. Study co-author Kirby Runyon, with Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said the IAU’s definition was erroneous since the literature review showed that clearing orbit is not a standard that is used for distinguishing asteroids from planets, as the IAU claimed when crafting the 2006 definition of planets. “We showed that this is a false historical claim,” Runyon said. “It is therefore fallacious to apply the same reasoning to Pluto,” he said. Metzger said that the definition of a planet should be based on its intrinsic properties, rather than ones that can change, such as the dynamics of a planet’s orbit. “Dynamics are not constant, they are constantly changing,” Metzger said. “So, they are not the fundamental description of a body, they are just the occupation of a body at a current era.” Instead, Metzger recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape. “And that’s not just an arbitrary definition, Metzger said. “It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body.” Pluto, for instance, has an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons, he said. The Daily Galaxy via University of Central Florida dailygalaxy.com/2018/09/new-rule-pluto-is-a-planet-its-more-dynamic-and-alive-than-mars/
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PLUTO
Oct 15, 2018 11:34:43 GMT -6
Post by auntym on Oct 15, 2018 11:34:43 GMT -6
curiosity.com/topics/heres-why-the-pluto-planet-debate-just-wont-die-curiosity/ Here's Why the Pluto Planet Debate Just Won't DieOctober 12, 2018 Written by Elizabeth Howell / A long time ago, a group of astronomers decided that Pluto was not a planet. This was in 2006, before the era of iPhones and Snapchat and Minecraft ... and yet scientists still argue over whether Pluto is a planet today. Why the big fuss? Let's dig in and find out, because the fate of our solar system's classification is at stake. No Scientific ConsensusPluto was disqualified from planethood because it was too small to clear debris nearby its path in space, or at least that's what the International Astronomical Union decided at a meeting in 2006. But a lot of people don't agree with that. After all, just look at the hundreds upon hundreds of asteroids threatening Earth; even our much larger planet can't clear all the little rocks nearby. A new paper in the journal Icarus brings up a fresh argument. Specifically: If we're talking about how to define a "planet," we should look at the literature of scientific papers to see what other scientists said. This is really important because literature is a part of how science works. A scientist makes a discovery, they submit it to a scientific journal, and then other scientists actually review their work before it gets published. Papers can be drastically altered before publication — or even never published at all, if they aren't valid in the eyes of the reviewing scientists. This "peer review" process is fundamental to science today and has been for hundreds of years. Here's the shocker in the new paper: The literature it reviewed about planets — all the way back to 1802, well before the invention of electricity — shows that only one single paper says that a planet needs to clear its orbit. And that methodology was later discredited! Where Do We Go from Here?The new paper's lead investigator is convinced we need to think differently about Pluto, especially after the NASA New Horizons spacecraft showed an incredibly complex world during its quick flyby in 2015. The spacecraft spotted signs of an underground ocean, ancient lakes, and even organic compounds — the building blocks of life — on the surface. "It [Pluto] is more dynamic and alive than Mars," said Philip Metzger, a planetary scientist at the University of Central Florida, in a statement. "The only planet that has more complex geology is the Earth." New Horizons principal investigator Alan Stern is a long-time advocate for calling Pluto a planet. Back in March, he and postdoctoral researcher Kirby Runyon co-authored an article in Astronomy calling for more flexibility on the definition of planet. Meanwhile, Stern, Runyon, and affiliates have been mounting a media campaign in recent months asking the IAU to reconsider their 2006 definition. This group says a planet should instead be defined as a round body that never underwent nuclear fusion. "At least 119 peer-reviewed papers in professional, scientific journals implicitly use this definition when they refer to round worlds (including moons) as planets. The publication history for these papers spans decades, hailing from both before and after the 2006 IAU vote," Runyon and Stern wrote in Astronomy. It's hard to say what will happen next, but one thing's for sure — after a dozen years, this debate is only getting louder and more forceful. In the end, what scientists decide upon could have huge implications. Under this new definition, we wouldn't have eight planets in the solar system; instead, there would be more than 100. So, Pluto lovers, here's the rub: If you get Pluto's planethood back, you also bequeath planethood upon dozens of sibling worlds. Talk about rewriting astronomy textbooks!
curiosity.com/topics/heres-why-the-pluto-planet-debate-just-wont-die-curiosity/
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PLUTO
Mar 28, 2019 12:52:03 GMT -6
Post by auntym on Mar 28, 2019 12:52:03 GMT -6
www.space.com/why-pluto-is-not-a-planet.html?utm_source=twitter&utm_medium=social&utm_campaign=dlvr.it Why Isn't Pluto a Planet Anymore?By Adam Mann / www.space.com/author/adam-mann3-28-2019 This artist's illustration shows Pluto and some of its moons, as viewed from the surface of one of the moons. Pluto shines as the large object at center, while Charon glimmers as a smaller disk to the right. Image released June 13, 2014. This artist's illustration shows Pluto and some of its moons, as viewed from the surface of one of the moons. Pluto shines as the large object at center, while Charon glimmers as a smaller disk to the right. Image released June 13, 2014. (Image: © NASA, ESA and G. Bacon (STScI))Textbooks had to be rewritten. Members of the public were outraged. Our understanding of the solar system itself was forever changed on Aug. 24, 2006, when researchers at the International Astronomical Union (IAU) voted to reclassify Pluto, changing its status from a planet to a dwarf planet — a relegation that was largely seen as a demotion and which continues to have reverberations to this day. Several years later, many still don't quite understand all the fuss, nor why Pluto was knocked from its planetary position. But the solar system's transformation from nine planets to eight was a long time in the making and helps encapsulate one of the greatest strengths of science — the ability to alter seemingly steadfast definitions in light of new evidence. What is a planet, anyway? The word planet stretches back to antiquity, deriving from the Greek word "planetes," which means wandering star. The five classical planets — Mercury, Venus, Mars, Jupiter and Saturn — are visible to the naked eye and can be seen shifting in strange pathways across the sky compared with the more distant background stars. After the advent of telescopes, astronomers discovered two new planets, Uranus and Neptune, which are too faint to spot with the naked eye. Pluto was found and classified as a planet in 1930, when astronomer Clyde Tombaugh of the Lowell Observatory compared photographic plates of the sky on separate nights and noticed a tiny dot that drifted back and forth against the backdrop of stars. Right away, the solar system's newest candidate was considered an oddball. Its orbit is so eccentric, or far from circular, that it actually gets closer to the sun than Neptune for 20 of its 248-years-long trip. In 1992, scientists discovered the first Kuiper Belt object, 1992 QB1, a tiny body orbiting out in Pluto's vicinity. Many more such objects were soon uncovered, revealing a belt of small, frozen worlds similar to the asteroid belt between Mars and Jupiter. Pluto remained the king of this region, but in July 2005, astronomers found the distant body Eris, which at first was thought to be even larger than Pluto. Size of Pluto (lower left) in comparison to Moon and Earth.Size of Pluto (lower left) in comparison to Moon and Earth. (Image: © Tom.Reding, CC BY-SA)Researchers had to ask themselves these questions: If Pluto was a planet, then did that mean Eris was one as well? What about all those other icy objects out in the Kuiper belt? Where exactly was the cut-off line for classifying a body as a planet? A word that had seemed straightforward and simple was suddenly shown to be oddly slippery. Intense debate followed, with many new proposals for the definition of planet being offered. "Every time we think some of us are reaching a consensus, then somebody says something to show very clearly that we're not," bob Marsden, a member of the IAU Executive Committee in charge of coming up with a new meaning for the word planet, told Space.com in 2005. A year later, astronomers were no closer to a resolution, and the dilemma hung like a dark cloud over the IAU General Assembly meeting in Prague in 2006. At the conference, researchers endured eight days of contentious arguments, with four different proposals being offered. One controversial suggestion would have brought the total number of planets in the solar system up to 12, including Ceres, the largest asteroid, and Pluto's moon Charon. The suggestion was "a complete mess," astronomer Mike Brown of Caltech, Eris' discoverer, told Space.com. Near the end of the Prague conference, the 424 astronomers who remained voted to create three new categories for objects in the solar system. From then on, only the worlds Mercury through Neptune would be considered planets. Pluto and its kin — round objects that shared the neighborhood of their orbit with other entities — were henceforth called dwarf planets. All other objects orbiting the sun would be known as small solar system bodies. The drama continuesA contingent of professionals did not take the decision lightly. "I'm embarrassed for astronomy," Alan Stern, a leader of NASA's New Horizons mission, which flew past Pluto in 2015, told Space.com, adding that less than 5 percent of the world's 10,000 astronomers participated in the vote. Such views are shared by many in the public. In 2014, experts at the Harvard & Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, debated different definitions of a planet. Science historian Owen Gingerich, who chaired the IAU's planet-definition committee, asserted that "planet is a culturally defined word that changes over time." But the audience watching the CfA debate overwhelmingly chose a different participant's definition — one that would have brought Pluto back into the planetary fold. Alternative classification schemes continue to pop up. A 2017 proposal defined a planet as "a round object in space that's smaller than a star." This would make Pluto a planet again, but it would do the same to the Earth's moon as well as many other moons in the solar system, and bring the total number of officially recognized planets up to 110. A year later, Stern, along with planetary scientist David Grinspoon, wrote an opinion article in The Washington Post arguing that the IAU's definition was "hastily drawn" and "flawed" and that astronomers should reconsider their ideas. But such pleas have fallen on deaf ears so far, and it seems unlikely the IAU will revisit the controversy any time soon. Astrophysicist Ethan Siegel responded to Stern and Grinspoon in Forbes by writing: "The simple fact is that Pluto was misclassified when it was first discovered; it was never on the same footing as the other eight worlds." Mike Brown also chimed in. "So, hey, Pluto is still not a planet. Actually, never was. We just misunderstood it for 50 years. Now, we know better. Nostalgia for Pluto is really not a very good planet argument, but that's basically all there is. Now, let's get on with reality," Brown wrote on Twitter, where he has embraced his role in the redefinition with the handle @plutokiller. MORE VIDEOS: www.space.com/why-pluto-is-not-a-planet.html?utm_source=twitter&utm_medium=social&utm_campaign=dlvr.it
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PLUTO
Apr 29, 2019 15:53:27 GMT -6
Post by auntym on Apr 29, 2019 15:53:27 GMT -6
www.space.com/pluto-planet-debate-2019-webcast.html?utm_source=twitter&utm_medium=social&utm_campaign=dlvr.it Pluto Planethood Debate Tonight! Here's How to Watch OnlineBy Elizabeth Howell / www.space.com/author/elizabeth-howell4-29-2019 LIVE 8:00 PM 4-29-2019Pluto used to be a full-fledged planet, and then in 2006 it wasn't. But the debate over its status continues, and you can watch one discussion live tonight. The International Astronomical Union's 2006 decision to demote Pluto to a "dwarf planet" takes center stage in a debate at 8 p.m. EDT (0000 April 30 GMT) by the Philosophical Society of Washington in Washington, D.C. You can watch live here, in the window above, or directly from the PSW Science group here. Alan Stern, the principal investigator of the New Horizons mission that flew past Pluto in 2015, has been a fierce advocate of Pluto remaining a planet. He will battle it out with Ron Ekers, a past president of the International Astronomical Union (IAU) who led the organisation from 2003 to 2006, when Pluto's demotion occurred. The IAU is the international body that governs the naming of celestial objects. Stern will discuss what he sees as scientific issues surrounding the definition for the term "planet," and he will propose a newer definition that is more inclusive of small bodies such as Pluto. Ekers will argue in favor of the IAU definition, which has a distinct taxonomy for little worlds that are far out in the solar system in a region known as the Kuiper Belt. The push to give planethood back to Pluto accelerated after the New Horizons flyby of the object, which revealed that Pluto had mountains, vast seas and other complex features. Stern argues that its geology is more reminiscent of a planet's than a smaller world's geology. www.space.com/pluto-planet-debate-2019-webcast.html?utm_source=twitter&utm_medium=social&utm_campaign=dlvr.it
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PLUTO
Apr 29, 2020 13:11:57 GMT -6
Post by auntym on Apr 29, 2020 13:11:57 GMT -6
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PLUTO
Jun 26, 2021 13:33:38 GMT -6
Post by auntym on Jun 26, 2021 13:33:38 GMT -6
9th ROCK FROM THE SUN9th Rock from the Sun Jul 14, 2015
The Late Show with Stephen Colbert
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Post by auntym on Feb 19, 2023 21:42:53 GMT -6
www.history.com/news/the-rise-and-fall-of-planet-plutoThe Rise and Fall of Planet PlutoLook back at the controversial decision to give Pluto the pink slip and shrink the solar system from nine planets to eight.CHRISTOPHER KLEIN UPDATED:AUG 22, 2018 ORIGINAL:AUG 24, 2016 Getty Images / NASA / Handout Percival Lowell knew something else was out there. Based on his calculations, the American businessman and astronomer was convinced that an unknown ninth planet was responsible for the wobbling orbits of Uranus and Neptune. For more than a decade until his death in 1916, Lowell peered into the shroud of darkness from the observatory he founded in Flagstaff, Arizona, but he never could find his elusive “Planet X” on the edge of the solar system.Then in the winter of 1930, as 24-year-old observatory assistant Clyde Tombaugh tediously compared photographs of a section of the night sky, he noticed a tiny speck of light on his plates had moved against the fixed background of stars. It was Planet X—right where Lowell calculated it would be. The Lowell Observatory announced its discovery of the ninth planet on March 13, 1930, the anniversary of its founder’s birth. At the suggestion of 11-year-old English schoolgirl Venetia Burney, the new planet was christened Pluto after the Roman god of the underworld, beating out other suggested names such as Minerva and Erebus. As astronomers learned more about Pluto, however, it turned out that the solar system’s outermost planet was a celestial oddball. It had the most elliptical and tilted orbit of any planet. At the closest point on its 248-year transit of the sun, Pluto passed inside the orbit of the solar system’s eighth planet, Neptune. While at the time of discovery, astronomers announced the distant planet “may be bigger than Jupiter,” Pluto turned out to be even smaller than Earth’s moon. Image of the nine-planet solar system. Getty Images / Image Source As more was learned about it, astronomers began to question whether Pluto had gained admission to the exclusive planetary club based on inflated credentials. Then in 1992, Massachusetts Institute of Technology scientists Jane Luu and David Jewitt discovered beyond Pluto’s orbit conclusive evidence of the Kuiper belt, a vast zone of debris left over from the formation of the solar system. Among the hundreds of celestial bodies orbiting the sun in the Kuiper belt were those similar in size and mass to Pluto. When Caltech astronomers led by Mike Brown discovered Eris, which had a greater mass the Pluto, in the Kuiper belt in 2005, it became clear that a change needed to be made to the membership of the solar system’s planetary club. When the International Astronomical Union (IAU) gathered in Prague in August 2006, the world’s top astronomical body considered a plan to expand the solar system to 12 planets with Pluto and its moon Charon, which is half its size, recognized as a twin planet. That measure was rejected, but with a show of hands on August 24, 2006, a majority of the IAU members present instead redefined a “planet” as a celestial body that orbits the sun, is generally spherical as a result of the force of its own gravity and must “clear the neighborhood around its orbit.” This third stipulation of the new planetary definition proved Pluto’s downfall as it lacked the sufficient mass to affect the orbits of Uranus and Neptune. CONTINUE READING: www.history.com/news/the-rise-and-fall-of-planet-pluto
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