The most beautiful phenomenon in the sky: Polar Aurora
When it occurs in the northern hemisphere, the phenomenon is known as the aurora borealis, a term originally used by Galileo Galilei referring to the Roman goddess of dawn, Aurora, and the titan that represents the winds, Boreas. It normally occurs between September and October and March and April. In the southern hemisphere, the phenomenon is called the Southern Aurora, after James Cook, a direct reference to the fact that it occurs in the south.
Even though auroras are best seen at night, they are actually caused by the Sun.
The Sun sends us more than heat and light; it sends lots of other energy and small particles our way. The protective magnetic field around Earth shields us from most of the energy and particles, and we don't even notice them.
But the Sun doesn't send the same amount of energy all the time. There is a constant streaming solar wind and there are also solar storms. During one kind of solar storm called a coronal mass ejection, the Sun burps out a huge bubble of electrified gas that can travel through space at high speeds.
When a solar storm comes toward us, some of the energy and small particles can travel down the magnetic field lines at the north and south poles into Earth's atmosphere.
There, the particles interact with gases in our atmosphere resulting in beautiful displays of light in the sky.
Oxygen gives off green and red light. Nitrogen glows blue and purple.
Do other planets get auroras?
They sure do! Auroras are not just something that happen on Earth. If a planet has an atmosphere and magnetic field, they probably have auroras. We've seen amazing auroras on Jupiter and Saturn.
These swirls of red light are an aurora on the south pole of Saturn.
The NASA Hubble Space Telescope took this picture of an aurora on Jupiter using ultraviolet (UV) light
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