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Get ready for a big moment in space.

NASA's New Horizons spacecraft will fly by Pluto to capture never-before-seen images at close range. The unmanned vehicle took nearly a decade to travel 3 billion miles from Earth to the dwarf planet.

Scientists are, pardon the pun — over the moon! — about what might be revealed in Tuesday's encounter. Pluto is the last of the classical nine planets to get an ambassador from Earth. It's icy, weird and full of unknowns. Some even say new data from the spacecraft could bolster a case for Pluto as a planet (it was demoted in 2006.)

At 7:30 a.m. ET, NASA will start streaming the flyby of Pluto on NASA TV. The stream doesn't offer live video because of the distance from Earth. But, the stream shows a simulated version of what NASA sees with a preview of what the flypast, estimated to take place at 7:49 a.m. ET, will reveal.

Scientists expect the craft to "phone home" by 9 p.m. Tuesday with real footage, including some highly anticipated images.

New Horizons' unmanned spacecraft propels through space at about 31,000 mph. Not long after its launch in 2006, it entered hibernation, where it remained for the better part of a decade. In December, scientists woke the machine up to start documenting the approach to Pluto.

The craft carries seven instruments that make thermal maps, check geology, capture interaction with solar wind and measure atmospheric composition.

And, if all goes according to plan, it will send new pictures!

No spaceship has ever visited Pluto. The Hubble Space Telescope can't even give scientists an accurate reading of the dwarf planet's size.

But, New Horizons can.

The craft sent back data in recent days already full of astonishing facts, revealing that methane and nitrogen ice cover Pluto's north pole, and that it could also be much larger than estimated.

Pluto and its smaller icy neighbors exist in the Kuiper Belt, a doughnut-shaped ring surrounding the sun. It is filled with hundreds of thousands icy bodies like Pluto and trillions of comets, according to NASA's website. Some even form thin atmospheres while orbiting closer to the sun.

Planets form by the joining of several masses. But, the Kuiper masses never joined, which means scientists can study these 4-billion-year-old forms to learn about the beginning of Earth's solar system. As far as scientists know, none of the masses support life.

New Horizons is the first mission to ever reach the belt.

Nine mementos traveled aboard New Horizons — yes, the number reflects Pluto's former classification as the ninth planet. The International Astronomical Union demoted it seven months after the spacecraft launched.

Among the items:

Ashes of American astronomer Clyde W. Tombaugh sit on board New Horizons. He discovered the then-planet 85 years ago. Tombaugh's widow and children gave an ounce of Tombaugh's ashes for the 2006 launch. They sit in a 2-inch aluminum capsule.

Also on board is a 1991 U.S. postage stamp that says, "Pluto Not Yet Explored." (This will lose truth Tuesday.)

Two state quarters on the flight — Maryland and Florida — represent the headquarters for flight control and launch site.

In 2006, the IAU downgraded Pluto from the solar system's ninth planet to a dwarf planet. Planets must meet three criteria:

Orbit around the sun
Structure that is round or nearly round
"Cleared the neighborhood," or is not surrounded by object of similar size and characteristic
IAU voted. Pluto didn't meet the third criteria. Several dwarf planets stay nearby and it can also overlap Neptune's orbit.

Some scientists argue that the IAU needs to reinstate it as a planet and hope this trip can provide supporting data to reinstate during Augusts IAU general assembly.

http://www.usatoday.com/story/tech/2015/.../30087043/

Luke Mauser

Surely it's also the case that Neptune overlaps Pluto's orbit, and therefore it is also not a planet?????
(07-14-2015 09:14 PM)Luke Mauser Wrote: [ -> ]Surely it's also the case that Neptune overlaps Pluto's orbit, and therefore it is also not a planet?????

Neptune's orbit is pretty typical of that of a planet. Pluto's is not. Pluto's orbit seems to have some similarities to a planetary orbit and some similarities to that of a comet.
(07-14-2015 09:14 PM)Luke Mauser Wrote: [ -> ]Surely it's also the case that Neptune overlaps Pluto's orbit, and therefore it is also not a planet?????

Neptune is a planet because it dominates its orbit. A planet must revolve around the Sun, be round, and be able to dominate its orbit gravitationally. Pluto strikes out on the third one. It doesn't dominate its orbit. That means it's a dwarf planet, or a planetoid. Ceres and Eris are planetoids as well. There's still a lot that's unknown about the Kuiper Belt. There might be lots of round objects in the Kuiper belt. If we didn't have the third rule about having to dominate its orbit, then how many planets would we eventually discover in the Kuiper belt? 20? 30?
Last I checked, the official definition was that it must have cleared its orbit, which, as much as Neptune fails that definition, so do Jupiter (trojan asteroids) and Earth (NEO's anyone?). In fact, I believe all of the gas giants have suites of trojan asteroids, at the lagrange points before and after their orbits
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