Dr. Chelsea Huang

Auroras happen when a solar storm happens,

This is when the sun releases a stream of very high-speed electrified gas to outer space.

And these gases are usually composed by electrons and protons.

And when this solar storm passes through Earth, some of the particles will get trapped by Earth's magnetic field.

And they will stream down along the magnetic field to the poles of Earth.

And these high-energy particles will hit Earth's atmosphere, excite the molecules in our atmosphere, and then cause them to emit light.

That's actually why you typically see auroras with different colors.

Green is actually mostly from oxygen, and sometimes oxygen also emits a little bit of red-orange light.

And then you would have blue and purple from nitrogen.

Is that right?

Yes.

So if you have any of these conditions, we expect the planet to have auroras.

And so what sort of planets do have these conditions?

The Hubble Space Telescope have imaged auroras on both Jupiter and Saturn.

The one on Jupiter's atmosphere is extremely interesting because on us, we typically expect the strength of auroras corresponding to the strength of solar wind.

Except on Jupiter, it also correlates with the orbital period of one of Jupiter's largest moons, Io.

So this is very interesting, because we believe Io has molten lavas underneath it, and Io interacts with Jupiter's magnetic field and creates some interesting connections between Io and Jupiter.

And these particular connected magnetic field interact with the solar wind and then amplify the auroras when the Io orbiting around Jupiter.

It just makes them more spectacular?

It makes it sometimes become stronger and sometimes becomes weaker while Io orbiting around Jupiter.