Outer solar system

    • Santa et al.
      When planetary scientists announced on July 29 that they had discovered a new planet larger than Pluto, the news overshadowed the two other objects the group had also found.
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    • Tenth Planet
      A planet larger than Pluto has been discovered in the outlying regions of the solar system. The planet is a typical member of the Kuiper belt, but its sheer size in relation to the nine planets already known means that it can only be classified
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    • Charon’s Occultation
      In a feat of astronomical and terrestrial alignment, a group of scientists from MIT and Williams College recently succeeded in observing distant Pluto's tiny moon, Charon, hide a star. Such an event had been seen only once before, by a single telescope 25 years
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    • Voyager I Reaches Final Frontier
      NASA's Voyager 1 spacecraft has entered the solar system's final frontier. It is entering a vast, turbulent expanse, where the sun's influence ends and the solar wind crashes into the thin gas between stars.
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    • Pluto’s Pair
      The evolution of Kuiper Belt objects, Pluto and its lone moon Charon may have something in common with Earth and our single Moon: a giant impact in the distant past.
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    • Planetoids Beyond Pluto
      Counting down the top ten astrobiology stories for 2004 highlights the accomplishments of those exploring Mars, Saturn, comets, and planets beyond Pluto. Number six in this countdown was the discovery of potential heat sources for ice beyond Pluto, an important finding if water is considered
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    • What Melted the Ice Planet?
      In October 2002, the Hubble Space Telescope first spotted an icy planetoid beyond Pluto. Named after an American Indian god, Quaoar, the planetoid should be far colder based on its distance from the sun than it appears to be.
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    • Vision of Neptune’s Triton
      Beyond the gas giants of Saturn and Jupiter, NASA plans its vision to explore the ice giants, like Neptune. While Titan attracts all the attention of moon watchers near Saturn, Triton intrigues those looking near Neptune.
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    • Stormy Uranus
      As the smallest of the gas giants, Uranus was thought from the Voyager probe flyby to have a relatively inactive surface. Stunning new images reveal storms the size of entire terrestrial continents and a faint ring.
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    • Beyond the Nine Planets
      The first detection of the faint distant object dubbed "Sedna" beyond Pluto may represent a new planet-like body with a moon. Looking up from Sedna's surface, the Sun would appear in the sky as the size of a pinhead.
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    • New Moon System Around Uranus
      Using the Hubble Space Telescope, astronomers have found two of the smallest moons yet in the Uranus satellite system. Measuring a minute eight miles, two of the small moons had previously eluded detection from the much closer view offered from the Voyager 2 flyby of
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    • Neptune Starts Forty-Year Spring
      Long-term observations of Neptune by the Hubble Space Telescope point to a changing season. When spring breaks on the ice-planet, it can last for decades. Cloud cover suggests that the planet's climate is changing.
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    • Fire and Ice
      Pluto, the only planet never visited by a spacecraft, is about to lose that distinction. NASA announced plans to visit the farthest reaches of our solar system, along with a journey to its innermost depths. Missions are now slated for fiery Mercury and to the
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    • Companions for Ice-Planet Neptune
      New moons have been found orbiting Neptune, one of our solar system's giant ice ball planets. The moons are the first found from ground-based telescopes in more than half a century.
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    • Beyond Pluto: Ice Planet
      The Hubble Telescope astronomers have found beyond Pluto, a distant object with the volume of all the asteroids combined. Unlike the long-contested 'Planet X', this candidate is one of a myriad of exotic, comet-like worlds (otherwise known as 'Kuiper Belt Objects', or KBOs).
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