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.

Principal investigator Alan Stern with the New Horizons aboard an Atlas V rocket in the background.
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.

Pluto in comparison to our Earth and Moon, and two bodies which are nearly certain to be dwarf planets.
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.




















10 Comments
Great article! Quick correction; at the current speed of 15.41km/sec (9.63 miles/sec) translates into 1.3 million km/day or 832,000 miles per day. Hard to imagine that even at these speeds and having been in space for over six years, there’s still three years to go before New Horizons arrives, or more correctly, flies past Pluto.
Planet or not, I still can’t wait to see what gets discovered.
“Unexpectedly for the IAU, there was a huge groundswell of public disagreement about little Pluto’s plight ” – only In the US – outside of the only country on THIS planet still not using the metric system, almost nobody cared. At least, it can be stated with certainty that almost the only voices still raised in protest are from the US. Several articles defending the reclassification and written by US citizens have suggested that primary reason IS emotion, related to the fact that Pluto was discovered by a US citizen.
Plenty of people outside of the US cared, including me. You’re just looking for an excuse to voice your pretty obvious anti-American views.
No, I’m not anti-US, except insofar as I am anti-nationalism and opposed to the concept of the nation-state in general. I was taking issue with the phrase “a huge groundswell of public disagreement” – that was a generalisation, and one that was largely only true in the US. As I also stated, the reclassification has been vigorously defended by plenty of US citizens too – I’d hardly be likely to mention that if I were on a US-bashing jihad. Pluto was once called a planet, now it’s called a dwarf planet, or a KBO. With increased knowledge, such recclassifications are inevitable, and happen in in every branch of science – who complains that elephants are no longer called pachyderms? It’s a defensible opinion to state that the “huge groundswell of public disagreement” mentioned above did/does only exist in the US.
“Patriotism is a pernicious, psychopathic form of idiocy.” G.B. Shaw
“Nationalism is an infantile disease, the measles of humanity.” Einstein
Sorry, Tony, but I’m not anti-US, except insofar as I’m vehemently opposed to the concept of the nation-state. Reclassification is a commonplace occurrence in science – I grew up when elephants were pachyderms, now they’re not. That doesn’t change the fact that they’re amazing animals. Likewise, the fact that Pluto’s been reclassified to be called a dwarf planet, a KBO, a TNO, or whatever, doesn’t diminish the achievement of New Horizons. I d took issue with the statement “there was a huge groundswell of public disagreement” because that was only true in the US, there was no such groundswell outside the US. As I said, the decision has been defended by many US scientists, does that make them guilty of anti-American views?
The reclassification of Pluto was “junk science” and will be undone in our lifetime. Rather than simply going to an obvious “minor planet” and “major planet” description of our solar system, the IAU decided to exert their pathetic influence as if they’ve made a lasting contribution to modern astronomy. The decision was made during a very political anti-American period (wars in Iraq and Afgan.) was not thought-out well at all…..since it just creates a very silly complicated series of gradient layers of classifications.
And Stuart, in a thousand years from now when our decendents look at the first images taken of the planet Pluto, they will know that they were taken by a craft designed and built and flown by the USA.
“in a thousand years from now when our decendents look at the first images taken of the planet Pluto, they will know that they were taken by a craft designed and built and flown by the USA.”
Those images will be of much greater significance than the classification given to Pluto. The amazing scientific and engineering feat that is New Horizons will ALWAYS be a real achievement, as was Tombaugh’s finding it. Calling Pluto a dwarf planet, a KBO, or anything else does not and will not diminish any of the science related to it. That’s why I find that brouhaha over the reclassification so very amusing. It would be fantastic if New Horizons could take a photo of Earth when it gets to Pluto, like the one Cassini took through the rings of Saturn, to put this “dwarf planet” fuss into perspective.
I know of one IAU member who publicly admitted he was coerced to vote to deplanetize Pluto back in 2006 in Prague. Also, the resolution was ramrodded thru on the last day of the General Assembly without proper vetting or notice, as required by the IAU’s own by-laws. If Earth was in Pluto’s orbit, it would not be a planet. Some say Pluto has a tail, and therefore, should not be a planet. Mercury has a tail. The obvious bias against Pluto in Prague is disturbing. I watched a video of the session in question and one pro-Pluto speaker was cut off in mid-sentence. The IAU had best reopen the debate or it risks becoming replaced by a new organization that will. By the way, current data suggests Pluto is larger than Eris by 7 miles in diameter.
[...] readers last heard about the New Horizons mission in April of last year [ “Sleeping at 34,000 Miles Per Hour” ]. We’re still two years away from the spacecraft’s observations of the Pluto system (and then [...]
Whether Pluto is called a planet or not is really inconsequential in the long run. When I was a schoolboy all we had were speculative artists depictions of the planets so every time I look at the images the various landers and probes have gotten I’m amazed. I’m sure this mission will be just as enlightening.