You are seeing stars — and even weirder, I can confirm that the green and red flashes of light in the heavens are not figments of your imagination!

It is not that you bumped your head, nor do you need glasses. And you are not hallucinating traffic lights in the night sky. This time of year, it is common to observe a light that appears to flicker in color, twinkling red and green low in the northeast sky.

Capella is to blame. It is a star system that contains two double pairs of stars, which produces the unique light show. There are two main reasons that this particular star system lights up the night in technicolor.

One reason is its size. The brightest star of Capella is about three times larger, 50 times brighter, and 80 times more luminous than our sun, though roughly the same temperature. In fact it is the sixth brightest (not counting our sun) star in the earth’s sky and the third brightest star in the northern hemisphere, after Arcturus and Vega.

Reflection and refraction are the other factors that cause the color. The atmosphere acts as a prism, so when the light from the stars shines though the earth’s atmosphere, it is bent and scattered, producing color. When the light source is low in the sky, as Capella is this time of year, the light passes through a larger cross section of atmosphere (compared to a star that is directly overhead), and thus the light is bent more, producing more color. Early evening is the best time to see this phenomenon.

Capella is located in the constellation Auriga. To locate this constellation, find the Big Dipper first. Look for the two top bowl stars of the dipper which will point you in the direction of Capella or just glance in the direction opposite the dipper’s handle.

The constellation Auriga is known as the Charioteer, with Capella being the goat. The translation of Capella from Latin means she-goat or nanny goat. South of Capella, find her kids, a little triangle of stars that is also a part of this constellation.

Roman mythology maintains that Capella represented the goat Amalthea (tender goddess), the foster mother that suckled Zeus. Amalthea broke its horn and filled it with flowers and fruits and gave it to Zeus. In thanks, he placed it in the sky together with the goats. This horn became the symbolic cornucopia, or horn of plenty, that fills itself with whatever one desires.

Regardless of your desires, there is plenty to see in the cornucopia of constellations that are found in the night sky. Take a cue from Capella’s celestial traffic lights — red means stop and green means go. In the case of the October night sky, stop what you are doing and go outside to see the stunning stars. And if the colorful beauty causes you to hear the music of the spheres, it just might be a capella.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.