Pluto may not be a planet any more, but it is still an important object in the hearts and minds of space enthusiasts, and a body filled with mysteries ripe for scientific investigation. On July 14 (future to the time of this writing, but past to the time of you reading it), NASA’s New Horizons spacecraft will pay a short visit to this cold body, aptly named after the Roman god of the cold, dead underworld. It will fulfil humanity’s long awaited goal of visiting all the major bodies in our solar system. And while Pluto, it turns out, is not alone in its vast region of space known as the Kuiper Belt—or the largest trans-Neptunian object, for that matter—it is still a meaningful goal to reach that once-planet that was still considered a planet when New Horizons launched.
Even if Pluto is not a planet, and it is becoming increasingly hard to justify its unique reputation beyond being the first Kuiper Belt object we happened upon, New Horizons’ mission can still be viewed as important; this is our first close look at the most numerous of all the bodies in the solar system. The Kuiper belt is estimated to contain hundreds of thousands of objects over 100 km in size, and potentially trillions of comets. So far, our only experience with these objects has been through pixelated Hubble Telescope images or encountering inner-solar system comets that have been drastically altered by their close encounters with the Sun. New Horizons offers a new opportunity to see these cold balls in their native habitat, as it were.
The spacecraft itself is an amazing piece of hardware. When it was launched in 2006, New Horizons set a record for the highest launch speed of an object leaving Earth. It then traveled over 5 billion kilometers to end up 5 light-hours away at the doorstep of Pluto. On July 14, New Horizons will speed past Pluto and its 5 known moons at 14 km per second, collecting a huge amount of data. Among its scientific instruments are MVIC, a colour camera; LORRI, a high-resolution black-and-white telescopic camera; and Alice, to perform ultraviolet spectroscopy of Pluto’s atmosphere. Since it took 9.5 years to get to Pluto, every major system—computers, guidance systems, and memory—was given a backup; you don’t want the entire mission to end before the probe even gets to its destination.
There are many questions that New Horizons is expected to answer. For instance, why is Pluto so much brighter than its largest moon, Charon? The Pluto-Charon system is also rather unique, as far as we know, for having a planet and moon so close in size. It is thought that Charon is made from the debris resulting from a collision between Pluto and another body. On both of those interesting properties, we have only one other example: the Earth and the Moon, so New Horizons will provide us with a fresh perspective on our own planet that the other major bodies in the solar system can’t bring us. After it finishes its rapid flyby, there is the possibility that New Horizons can use its remaining fuel to steer towards another Kuiper Belt object for another rendezvous in a few years. And in the meantime, it will remain a source of wonder and discovery as all of the data collected from the Plutonian system is downloaded and analyzed over the many coming months.
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