If this image makes you think of the Northern Lights, you shouldn’t be surprised. Because this is in fact a planeterrella: a large glass dome containing spheres and charged particles, which mimics the auroral glows present within our solar system.
When magnetic fields are applied within the dome, put together by NASA, charged particle of nitrogen in the air around the spheres glow purple. That’s in contrast to the real Northern Lights, which tend to glow green because of oxygen in the atmosphere.
Colour aside, the planeterrella isn’t just pretty — it’s useful too. Guillaume Gronoff of the NASA Langley Research Center explained to New Scientist:
[W]e can show the reaction when Io, the satellite of Jupiter, sends particles to Jupiter. We can also simulate the aurora at Neptune and Uranus, when their magnetic fields are directly pointing towards the sun…
Pretty neat for an experimental setup inspired by a 19th-century experiment called the terrella, in which a single sphere was used to show how the Earth’s magnetic field accelerates electrons. Soon, Gronoff is going to add more magnets and a little CO2 to replicate the auroras on Mars. [New Scientist]