It’s sleeping, and only about the size of a piano. Yet it’s careening to the edge of our Solar System at an awesome 34,000 miles per hour. It’s the New Horizons spacecraft, covering
nearly a million over 1.3 million kilometers a day, on a historic voyage to Pluto — ‘asleep’ in a state of hibernation to conserve energy.
In fact — besides setting the record for the fastest launch speed of a man-made object (36,373 mph) — New Horizons is breaking a new record every second. Since December 2nd, 2011, it’s been the closest spacecraft to approach Pluto (when it passed a previous mark set by Voyager 1 in January 1986). So every moment it travels, it sets a new mark for nearest approach.
Launched in January, 2006, NASA’s robotic spacecraft is the first mission to Pluto — which, at the time, was the only planet in orbit around our Sun left unexplored. But a funny thing happened about six months after leaving Earth, while New Horizons was busy traversing the Asteroid Belt; Pluto got demoted.
The International Astronomical Union (IAU) made a now infamous decision to reclassify Pluto to dwarf planet status — a new subcategory. The Solar System planet club dropped instantly from nine to eight. And the wound has not healed, for reasons that have to do with good science, not emotion.
As Principal Investigator for New Horizons, Alan Stern, explained in an interview with EarthSky:
Pluto, and its cohorts, are planets. They have all the attributes of planets. They have cores. They have geology. They have seasons and atmospheres. They have clouds. They have polar caps in many cases. They have moons.
I can’t think of a single distinguishing characteristic that would set apart Pluto and other things that you’d call a planet, other than its size. So I like to say, a Chihuahua is still a dog.
Unexpectedly for the IAU, there was a huge groundswell of public disagreement about little Pluto’s plight — at a level unprecedented for a scientific announcement about simple categorization. Maybe folks like to cheer for the underdog, but it seems that Pluto has quite a loyal following with kids and adults alike — and from the sidelines of the debate, people let the IAU know that they thought the demotion was wrong.
Planet or not, Pluto is going get a curious visitor very soon. New Horizons continues its lonely journey unperturbed by the IAU’s controversial decision. At the end of April, scientists will nudge it awake for a month of routine systems testing, then the tiny probe will slumber some more — a rhythm that will continue until it arrives in July 2015.
The Pluto system is an unseen mystery. Below is a CG animation of what the surface — and its largest moon Charon — may look like. Is it accurate? We’ll know for sure in about 3 years.
Thanks to W. Thomas Leroux for the mathematical correction in the 1st paragraph of this article.
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