One of the great wonders of the night sky is the exquisite light display known in northern latitudes as the northern lights or aurora borealis, after the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas. In southern latitudes it is known as the southern lights or aurora australis, from the Latin word meaning “of the south.” The display may take the form of a diffuse glow or of great curtains of light, and may appear static or to be changing constantly. The most common color for auroras is green. Less common are pink, light green mixed with red, pure red, yellow, with the rarest being blue. Auroras are most commonly visible at night within a ring just within the Arctic and Antarctic circles. They most often occur near the equinoxes, the time of year in the spring and fall when the length of day and night are equal. Auroras have even been observed on other planets.
So what exactly is the aurora, and how does it work? The intense heat of our Sun causes a flow of hot plasma (free electrons and protons too hot to form atoms) to radiate in all directions, including towards our Earth. We call this flow of charged particles the solar wind. When the solar wind encounters the earth’s magnetic field these particles flow towards the earth’s magnetic poles where the lines of magnetic force are greatest, and accelerate towards Earth. Collisions between these charged particles and nitrogen and oxygen atoms in the Earth’s upper atmosphere result in the release of energy in the form of photons of light. The color of the resulting aurora depends in part on the amount of energy involved in the collision and also on whether the collision involves oxygen or nitrogen atoms. During periods of heightened sun spot activity auroras occur more often, appear brighter, and are sometimes visible at more temperate latitudes than usual, including here in southern New England. This is because the greater intensity and frequency of coronal mass ejections resulting from sun spots increase the intensity of the solar wind. While the next peak is due around 2013, it is not expected to be as intense as the last one in 2001. People have been in awe of the aurora for centuries, attributing to it magical powers and origins. Today, despite our scientific understanding of the phenomenon, it is still a wonder to behold.
This month join the Springfield STARS Club for movie night. The documentary The Journey to Palomar will be shown on Tuesday, November 23rd at 7:30pm at the Springfield Science Museum at the Quadrangle. This remarkable film tells the story of astronomer George Ellery Hale as he strives to build some of the greatest telescopes of the 20th Century, culminating in the construction of the giant 200-inch telescope on Mount Palomar, beginning in the 1930s. His observations changed the way we view the universe. Refreshments will be served, and the public is welcome free of charge.
Copyright © Amanda Jermyn