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A planet is a planet wherever it resides, right? Dave Eicher examines the case of the icy world.In 1930 a young astronomer from Kansas, employed as an observer at Lowell Observatory in Arizona, discovered Pluto. It was the first planet in the solar system to have been discovered since 1846, when astronomers in Germany detected Neptune. Clyde Tombaugh, just 24 at the time, was hailed as a hero, Disney named a cartoon dog after the new planet, and for 76 years the solar system was a happy place. And then, in 2006, the International Astronomical Union (IAU) reconsidered Pluto’s status....

Pluto is a dwarf planet. A dwarf planet travels around, or orbits, the sun just like other planets. But it is much smaller. Clyde Tombaugh discovered Pluto in 1930. He was an astronomer from the United States. An astronomer is a scientist who studies stars and other objects in space. Venetia Burney named Pluto that same year. She was an 11-year-old girl from England. Pluto is not very big. It is only half as wide as the United States. Pluto is smaller than Earth's moon. This dwarf planet takes 248 Earth years to go around the sun. If you lived...

Southwest Research Institute scientists integrated NASA's New Horizons discoveries with data from ESA's Rosetta mission to develop a new theory about how Pluto may have formed at the edge of our solar system. "We've developed what we call 'the giant comet' cosmochemical model of Pluto formation," said Dr. Christopher Glein of SwRI's Space Science and Engineering Division. The research is described in a paper published online today in Icarus. At the heart of the research is the nitrogen-rich ice in Sputnik Planitia, a large glacier that forms the left lobe of the bright Tombaugh Regio feature on Pluto's surface. "We...

Pluto and its large moon Charon may have been bowled over when they were struck by wayward space rocks in the past, a new study suggests. If so, NASA's New Horizons spacecraft may find evidence of these rolls when it arrives at the distant worlds in 2015. Jay Melosh of the University of Arizona in Tucson, US, first suggested about 30 years ago that the basins gouged out by impacts would redistribute the mass of planetary bodies, causing them to roll over to re-stabilise themselves... Now, Francis Nimmo of the University of California in Santa Cruz, US, who led the...

If David J. Tholen (University of Hawaii) is right, Pluto was probably hit by a small Kuiper Belt object in the not-too-distant past. One consequence of that collision, he argues, is seen in the planet's motion -- Pluto and its satellite Charon now waltz around each other in slightly out-of-round orbits. And since tidal forces in the tight planet-moon system should damp out any deviations from purly circular orbits within 10 million years or so, the impact must have occurred relatively recently. "It could have happened a century ago," Tholen says... Tholen and Marc W. Buie (Lowell Observatory)... found an...

Pluto is an uncanny-valley world, with landscapes and vistas that seem strikingly similar to those of Earth — until you take a closer look. NASA's New Horizons mission, which flew by the dwarf planet in July 2015, found that Pluto has towering mountains, but of water ice rather than rock; vast plains of frozen nitrogen and other exotic materials; and blue skies provided by a wispy atmosphere that contains no appreciable oxygen. And now, a new study reveals another alien parallel: Pluto has an extensive dune system, but the grains that make up the wind-blown mounds are certainly not sand....

-snip- The researchers found 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, this reason is no longer considered a factor that determines if a celestial body is a planet.“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,” said Dr. Kirby Runyon, from the Johns Hopkins University Applied...

August 24, 2006 was a dark day for Pluto enthusiasts. It was on that day that the International Astronomical Union established three conditions a celestial body must meet in order to be considered a planet. A planet must orbit around the sun, it must be massive enough to be rounded by its own gravity, and it must have “cleared the neighborhood” around its orbit, which means, simply put, that it must have a certain amount of gravitational pull. Pluto does not meet the third condition, so once those rules were put in place, Pluto was demoted to “dwarf planet,” 75...

At last, NASA's New Horizons spacecraft is sending back images of Pluto that look (slightly) better than brown blobs or pixel art. The probe has delivered a new batch of images from between 7.8 million to 9.2 million miles away, or close enough that the dwarf planet is starting to reveal some meaningful detail. There's still no explanation for those giant spots, but it's evident that there's a "continuous swath" of dark ground near the equator. And if you'd like pictures that are better than fuzzy, you might not have to hold out for too much longer. New Horizons...

Ceres is the largest object in the asteroid belt, and NASA's Dawn spacecraft will arrive there on March 6. Pluto is the largest object in the Kuiper belt, and NASA's New Horizons spacecraft will arrive there on July 15... The efforts of a very small clique of Pluto-haters within the International Astronomical Union (IAU) plutoed Pluto in 2006. Of the approximately 10,000 internationally registered members of the IAU in 2006, only 237 voted in favor of the resolution redefining Pluto as a "dwarf planet" while 157 voted against; the other 9,500 members were not present... Unlike the larger planets, however,...

The dwarf planet Pluto and its system of five moons are about as mysterious as the underworld of antiquity that inspired their names. ... “We are still baffled by how the system formed,” says study co-author Mark Showalter, a senior research scientist at the Search for Extraterrestrial Intelligence (SETI) Institute. “I think everyone believes that, at some point in the distant past, a large object bashed into ‘proto-Pluto’ and the moons formed out of the debris cloud. However, after that point in the story, details get very sketchy.” Now, analysis of data collected from the Hubble Space Telescope following the...

Puto Video http://cdn.theguardian.tv/mainwebsite/2015/04/16/150416pluto_desk.mp4 Pluto’s moons have been tracked closely for the first time, showing that they tumble unpredictably rather than keeping one face fixed on their host planet. Astronomers also observed that Pluto, whose status was downgraded to a dwarf planet in 2006, might be better regarded as a binary dwarf as it is locked in orbit with its largest moon, called Charon. The twin system creates an imbalanced and shifting gravitational field, which sends the tiny outer moons spinning chaotically, the measurements from the Hubble space telescope showed. Target Pluto: fastest spaceship set for epic encounter with our remotest...

n July of this year (2015), NASA’s New Horizons mission will fly past Pluto and its moons. It will map the surface of the Plutonian system in unprecedented detail, revealing craters and other surface features for the first time. In preparation for the deluge of newly discovered craters, mountains, crevasses and other surface features, Mamajek et al. discuss a naming system for Pluto and its moons. Pluto is one of the last large planetesimals in the Solar system to have its surface imaged in detail. Pluto’s surface features will reveal the history of its life in the alien conditions at...

I count myself among the many astrogeeks who (1) keep track of where all the visible planets are and who (2) hold a considered opinion regarding whether Pluto should have been downgraded from full planet status. (BTW, yes, Pluto deserves the demotion to dwarf planet; not just because it is even smaller than the dwarf planet Eris, but also because Pluto can’t walk upright like Goofy). This month provides particularly interesting evenings for stargazers. Five planets — Mars, Neptune, Venus, Uranus, and Mercury — are all bunched up within a few degrees of each other from the perspective of Earth....

A theory is hereby proposed that an unknown mega-massive planet has, for billions of years, been orbiting at 77.2 AU from the sun -- within a 44 AU-wide, virtually empty Great Void that surrounds the Kuiper Belt (One AU = 93 million miles, the mean Earth-Sun distance). The Void is postulated to have been formed by strong gravitational attraction of the unknown planet having removed all CKBOs (Classical Kuiper Belt Objects) that had existed previously in the vicinity of the massive planet's huge orbit... The 77.2 AU distance from the sun of the proposed unknown planet is derived from a...