|Image assembled from Clker clip art and a NASA image of the M-81 galaxy.|
Most stars congregate into gravitationally bound structures called galaxies. The sun is part of the Milky Way, a large galaxy containing about two hundred billion stars. It is about one hundred thousand light years across. Dwarf galaxies are much more numerous than large galaxies. Green peas are a rare type of dwarf galaxies, which are, at most, 10% the size of the Milky Way.To read the rest of the article in context, peas click on "Are Green Pea Galaxies a Problem for Creationists?" Much obliged, pod-ner.
The name for green peas comes from their round shape and green color. A galaxy’s color normally is a composite of its stars’ colors. But stars never appear green, so how do green peas get their distinct color? Indeed, it is this question that led to the recognition of the green pea class of galaxies less than a decade ago. The answer lies in very strong emission at a wavelength of 500.7 nanometers (a nanometer is one-billionth of a meter). This is smack in the middle of the green part of the spectrum, and the emission is so strong that it dominates the light of pea galaxies. The emission comes from doubly ionized oxygen in the interstellar medium, the space between the stars in the galaxy.