By: Matthew Wheeler
This is a historic week in humanity’s discovery of our surroundings, as the last of the familiar objects in our solar system gets a visit from Earth. The New Horizons spacecraft is taking our knowledge of Pluto and its moons from barely more than distant points of reflected sunlight to richly detailed icy landscapes. The robotic spacecraft is traveling so fast–it would go from Dunster to Valemount in 4 seconds–it has only a few hours near Pluto. With radio signals taking more than 4.5 hours to reach Earth, it had to be trained in advance to make all the studies it can on the flyby.
This will likely be the only close look at the dwarf planet for a generation, and in a way completes a chapter in more than five decades of sending spacecraft to the textbook objects of our solar system: planets, sun, moons, asteroids and even comets.
Before rocketry, it was the telescope that revolutionized our knowledge and enjoyment of the universe. It was 405 years ago that Galileo first looked at Jupiter through a telescope and found it had four moons in orbit. He found Venus showed phases of illumination just like our moon. These put an entirely different spin on the ancient idea that everything in space moved around the Earth, and gave proof to theories that the sun is the centre of the solar system, not the Earth.
The telescope made possible the discovery of giant planets Uranus and Neptune. Oddities in measurements of their orbits led astronomers to look for more planets, but it took nearly a century for the next discovery. Astronomer Clyde Tombaugh was given the job of taking photos of likely parts of the sky, and in early 1930, when viewing pairs of photos taken on different days, he found a faint point of light that had moved, relative to the background of stars, with an orbit beyond Neptune.
Ideas for this new planet’s name were sent in from around the world. It was the suggestion of an eleven year old girl, Venetia Burney, that astronomers chose and is so familiar: Pluto.
How far reaching was Venetia’s suggestion? It appears the name of a famous cartoon dog was inspired by her choice later that year, and the planet’s name was given to a highly radioactive element synthesized in 1940: plutonium. Oh, and when you are trying to take good photos in dusky light, think of the New Horizons spacecraft. At Pluto the sunlight is 900 times dimmer than here on Earth. Not just a challenge to making blur-free photos when you are going more than 43,000 km per hour, that light is far too dim for solar panels to provide power, so decay of a radioactive element provides the robot’s heat and modest electricity supply. That element? Plutonium.
Talking of far reaching, Pluto’s discoverer Clyde Tombaugh is making history of another kind: some of his ashes are on board the New Horizons spacecraft.
To give an idea of the challenge of this voyage, if you visit McBride’s scale model solar system, where the sun is a street lamp by the railway station and Earth is like a peppercorn along the first block, the dwarf planet Pluto would be a sand grain on the Fraser River bridge.
This summer keep watching as another dwarf planet, Ceres, gets a close up visit from the Dawn spacecraft, and the drama of a comet heating up on approach to the sun is seen by Rosetta and the first ever comet lander Philae. Links to all these events and maps of McBride’s model solar system can be found at visitmcbride.ca