M-16 Eagle Nebula

Nebula

Nebulae are clouds of dust and gases located within our own galaxy. Some of these nebulae are regions where new stars are being born. Others are actually created by the explosions of dying stars. The gases in some nebulae are hot enough to produce their own light. Other types of nebulae are lit up by nearby stars...like a headlight in the fog.

What is H-alpha?

Hydrogen is the most common gas in a nebula. When starlight energizes it, the hydrogen gives off light at a few exact colors. The brightest is a deep red called H-alpha, at a wavelength of 656.3 nanometers, near the red edge of what our eyes can see.

An H-alpha filter lets through only a very narrow band of light around that one color and blocks the rest. The glowing hydrogen clouds stand out clearly, while most other light, including city light pollution, is cut out. That's why these images show the nebula's red, glowing gas in such detail.

Source: Hydrogen-alpha, Wikipedia