ROCHESTER, N.Y. (WROC) — On Sunday night, for those who were out late and had a clear view north, brilliant greens, reds, and even some purples danced across the sky. For those few, they caught a rare, for our area, glimpse of the Aurora Borealis, more commonly known as the Northern Lights.

What causes the aurora?

One of the key players in the aurora, even though it’s dark when you can see it, is the sun. Without it, none of this would be possible. The sun, if you didn’t know, is a giant reactor producing tons and tons of energy through a process known as fission. Occasionally, not all of this energy can be contained by the sun’s magnetic field, and bursts of energy can erupt from the sun and head toward the earth. These bursts are called solar flares, everything that is ejected with it is referred to as a coronal mass ejection (CME).

The CME is made of plasma, the fourth state of matter which in this case is composed of charged, or ionized particles, of helium and hydrogen. Also embedded in the plasma are loose electrons, which hold a negative charge, and protons, which hold a positive charge. As these race towards earth, they eventually hit what’s known as the magnetosphere, or earth’s magnetic field which is produced by the core of the planet.

A diagram of the earth’s magnetic field. The sun-facing side is compressed due to the solar wind, a constant stream of plasma that is emitted from the sun.

The magnetic field then draws the charged plasma to the north or south poles, and as it descends into the atmosphere, the electrons, or negatively charged particles, begin to collide with the nitrogen and oxygen atoms. This collision results in a release of energy, in the form of, you guessed it: Light!

The different colors of the aurora are caused by this process too. Depending on what gasses the electrons are colliding with, and at what height in the atmosphere determines if you’ll see just the eerie green glow or more brilliant reds, pinks, and purples.