[meteorite-list] Honey, I Shrunk the Solar System

From: R. N. Hartman <rhartman04_at_meteoritecentral.com>
Date: Thu Aug 24 20:05:25 2006
Message-ID: <001801c6c7da$3b44f250$6401a8c0_at_ronij3wi4b7cpv>

<<It must orbit the sun, be massive enough that its own gravity pulls it
into a nearly round shape,>>

So if it has the shape of a dinner plate it is a planet? It would be a
strange object, indeed! :=)

----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Thursday, August 24, 2006 2:42 PM
Subject: [meteorite-list] Honey, I Shrunk the Solar System


>
> http://www.nasa.gov/vision/universe/solarsystem/planetsf-20060824.html
>
> Honey, I Shrunk the Solar System
> August 24, 2006
>
> Media contact: Jane Platt/JPL
> (818) 354-0880
>
> If you woke up Thursday morning and sensed something was different about
> the world around you, you're absolutely right. Pluto is no longer a
planet.
>
> The International Astronomical Union, wrapping up its meeting in Prague,
> Czech Republic, has resolved one of the most hotly-debated topics in the
> cosmos by approving a specific definition that gives our solar system
> eight planets, instead of the nine most of us grew up memorizing.
>
> NASA has already visited all eight planets that retain their official
> title: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
> In addition, the agency has its New Horizons spacecraft en route to
> Pluto, which the astronomical union has designated as the prototype for
> a new class of celestial objects, to be called "dwarf planets."
>
> "NASA will, of course, use the new guidelines established by the
> International Astronomical Union," said Dr. Paul Hertz, Chief Scientist
> for the Science Mission Directorate at NASA Headquarters. "We will
> continue pursuing exploration of the most scientifically interesting
> objects in the solar system, regardless of how they are categorized."
>
> Ceres, which orbits in a belt between Mars and Jupiter and is the
> largest known asteroid, is one of those interesting objects. In 2007,
> NASA will launch the Dawn spacecraft on a mission to study Ceres, which
> the astronomers have placed in the dwarf planet category, alongside
> Pluto. The dwarf planet family also includes 2003 UB313, nicknamed
> "Xena." When Dr. Mike Brown of Caltech and his colleagues announced last
> summer that they'd discovered the object, which is bigger and farther
> away than Pluto, many astronomers decided it was time to figure out once
> and for all, "What exactly is a planet, anyway?"
>
> Here's how it all shakes out. The International Astronomical Union has
> decided that, to be called a planet, an object must have three traits.
> It must orbit the sun, be massive enough that its own gravity pulls it
> into a nearly round shape, and be dominant enough to clear away objects
> in its neighborhood.
>
> To be admitted to the dwarf planet category, an object must have only
> two of those traits -- it must orbit the sun and have a nearly round
> shape. And no, moons don't count as dwarf planets. In addition to Pluto,
> Ceres and 2003 UB313, the astronomical union has a dozen potential
> "dwarf planets" on its watchlist.
>
> What's to become of the other objects in our solar system neighborhood,
> the ones that are not planets, not dwarf planets and not moons? The
> organization has decided that most asteroids, comets and other small
> objects will be called "small solar-system bodies."
>
> Despite the establishment of these three distinct categories, there are
> bound to be gray areas. As technologies improve and more objects are
> found, the International Astronomical Union will set up a process to
> decide which of the three categories are most appropriate for specific
> objects.
>
> Even before the discovery of Xena, not all was calm in the planetary
> world. There was debate after Clyde Tombaugh discovered Pluto in 1930.
> With its small size, distant location and odd orbit, some questioned
> whether Pluto was really a planet or just an icy remnant of the
> planet-forming process.
>
> That issue has been resolved by the International Astronomical Union.
> Among those most keenly following the debate -- Mike Brown, who has been
> awaiting word on Pluto and the object he found, Xena.
>
> "I'm of course disappointed that Xena will not be the tenth planet, but
> I definitely support the IAU in this difficult and courageous decision,"
> said Brown. "It is scientifically the right thing to do, and is a great
> step forward in astronomy."
>
> Although the revamping of our solar system might seem unsettling, it's
> really nothing new. In fact, when Ceres was first discovered in 1801, it
> was called a planet, as were several similar objects found later. But
> when the count kept on growing, astronomers decided "enough is enough,"
> and they demoted Ceres and its siblings, placing them in a new category,
> called asteroids.
>
> The International Astronomical Union has been naming planets and moons
> since its founding in 1919. For more information, visit the
> International Astronomical Union home page at www.iau.org
> or www.iau2006.org .
>
>
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Received on Thu 24 Aug 2006 08:05:51 PM PDT