The Pluto Encounter: A View From Afar!
Next week on July 14, the NASA spacecraft New Horizons will have completed its nine-year journey to Pluto. There is no telling what we will discover when we get there, but it will certainly be both alien and exciting!
For most of the 70 years since Clyde Tombaugh first discovered it in 1931, Pluto has been nothing more than a smudge of light even through the most powerful telescopes. For decades, we didn’t even know if it was the size of Earth, or the size of a large asteroid! Even less was known about its mass, but we certainly knew a lot about its orbit!
At 39 times the distance of our Earth from the Sun, those 5.8 billion kilometers translate into a 238-year orbit. In Earth’s sky, the planet moves about the diameter of the full moon every four months. When as a student I first learned about Pluto, it was in the constellation Leo, but now it is way over in Sagittarius! Its enormous distance also promised that at about 40 kelvins (-233 Celsius), it would be the coldest object in the solar system since it experiences 1/1000 the warming sunlight falling on Earth’s surface. High Noon on Pluto is scarcely brighter than twilight on Earth. (Check out NASA’s
The sun from Pluto according to an artist! (Credit: ESO/L. Calçada)
It was also a huge technological feat to get anything to travel that far from Earth and still work! Electrical power could not come from solar panels as was common for space craft flying across the brilliant inner solar system. Solar panels near Pluto would have to be 900 times bigger to collect the same solar energy. So NASA went nuclear by using radioisotope thermoelectric generators (RTGs), whose decaying plutonium generated heat, and from this, a feeble but —> Read More