After almost nine and a half years of travelling, the New Horizons probe is almost at Pluto (July 14th closest approach)! Whatever happens in the next few days, New Horizons will always be a unique mission: when it launched (January 2006) Pluto was still a planet… not so when it arrived!
Lots of people ask why astronomers “demoted” Pluto to the status of a dwarf planet. Why couldn’t we just have kept it at the same status? We could get into the formal definitions of what a planet is now considered to be, but there’s no point in doing that here (after all, the fact there was a *vote* means that not everyone agreed!). What’s more important, IMHO, is that the astronomers put the scientific consensus above historical, monetary and personal concerns. And that’s how science should work.
But really, the issue is pretty moot! What we choose to call Pluto hasn’t changed what it is, and heck, we’re about to find at a whole whack of a lot more about it over the next few days. Even the best shots we have from the Hubble of Pluto are blurry…
– Oh, and while we’re at it… Where did the name for Pluto (discovered in 1930 by American astronomer Clyde Tombaugh) come from? It isn’t that well known but it was actually suggested by an 11 year old girl named Venetia Burney. She passed away in 2009 –
At its closest approach New Horizons will be a mere 13,000 km above the surface of Pluto – that’s almost the same distance as flying from Los Angeles to Melbourne Australia. That might sound like a lot to us Earthbound humans, but on the scale of the solar system it is tiny. When you consider the distance of Pluto from the Earth, it’s the equivalent to the width of a hair at 50 metres! And what’s the fly-by speed? A “mere” 59,000 kph – about 70 times faster than a commercial jet.
So what are we going to learn? Well by the standards of Voyager and Pioneer, New Horizons is a pretty small probe. It’s about the size of a grand piano.The scientific payload, i.e. the thing that you want to actually get to the planet(!), has a mass of only 30 kilos – about half the mass of a person. Obviously one of the key components are cameras. They work at a number of different wavelengths to help us determine not only how the surface looks but also what it’s made of. There’s also a radio transmitter named REX that will beam radio waves through the atmosphere of Pluto back to the Earth. From the received signals we’ll be able to determine the structure of the atmosphere (and it will also help us look for an atmosphere around the moon Charon).
There will also be instruments that measure how Pluto interacts with the solar wind from the Sun, but perhaps the most intriguing instrument on board is the Venetia Burney (remember her?) student dust counter. This experiment, designed and conceived by students at the University of Colorado, Boulder, will measure the size of dust particles around Pluto (the space between planets isn’t completely empty…!)
And New Horizons mission doesn’t just stop at Pluto. Astronomers involved in the mission have been using the Hubble Space Telescope (and others) to find other icy bodies in the outer regions of the Solar System (the “Kuiper Belt“) that the probe could visit. Of course, they have to be in the right place, New Horizons is travelling so fast that only small course corrections are possible. Right now, the best candidate for another rendezvous suggests we’ll have to only(!) wait 4 years!
But the next few days are really the most important part of the mission. We’re about to learn a whole heck of a lot more about Pluto – can’t wait!