The recent Pluto probe presented a problem for NASA engineers. Spacecraft that are reasonably close to the sun, such as India's Mars Orbiter Mission, use solar panels to supply their electricity. But when you get out to Pluto, the sun is so dim it's barely distinguishable from the rest of the stars.
As Sir Martyn Poliakoff explains, as done before with the Voyager probes, the engineers substituted solar panels for a big hunk of radioactive plutonium. That produces heat, which can be used to generate electricity, and it also keeps the spacecraft warm. The whole thing is rather appropriate given that plutonium was named after the dwarf planet in the first place. Watch the full explanation in the video below. Ryan Cooper
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