The Importance of Astronomy Light

Light is crucial to astronomy – not just for human eyes but also for telescopes, cameras, and other instruments. Whether it’s visible light, infrared, or radio waves, astronomers use this energy to study the Universe. The visible part of the electromagnetic spectrum contains all the colors of the rainbow. The shorter wavelengths correspond to blue, the longer ones to red and everything in between. Most celestial objects emit some visible light.

Stars, for example, glow in the visible light from their hot, glowing cores and radiate invisible light that astronomers detect in other ways, such as radio waves. Other stars and planets give off a glow called infrared light when their atoms or molecules absorb and radiate this energy. And, like a mirror reflecting the Sun’s rays, the surfaces of these objects reflect different colors of light depending on their composition and how that light hits their surface.

This is called scattering. Light that reflects off a surface can have properties that tell scientists about the materials on that surface. For example, the way Mars reflects light can tell astronomers about its mineral composition and whether it has water or rock on its surface. And, when high-energy particles bombard a planet’s magnetic poles, they can create beautiful displays of ultraviolet light in the form of auroras, as seen by Hubble on Jupiter.

Then there are the invisible parts of the spectrum that astronomers can detect by using special instruments. For instance, when a galaxy or other cosmic object emits radiation at the same frequency as a nearby star, it leaves behind a trail of “light echos.” This echoes are observed with an infrared camera and reveal the location of the source.

Astronomers can also use light echoes to find out what a galaxy or other distant object has done in its past. They can also measure the size of objects by looking at a pattern of dark lines in a spectrum, called a spectrogram. These patterns of dark and bright lines are like fingerprints for atoms and molecules. By studying these, astronomers can unlock secrets about an object’s composition, temperature, and even its age.

The most common source of astronomy light is our own star, the Sun. But, a telescope can also catch light from other sources in the Universe. This includes other galaxies, star clusters, and individual stars and planets. For this reason, it is important to protect the skies from unnecessary light pollution. Light pollution distorts the natural spectrum and washes out and obscures the faint, fuzzy nebulas, stars, and galaxies that we see when looking at the night sky. In addition, certain types of lights (such as low-pressure sodium, or LED) can interfere with astronomical observations. The best lights to use around the house or observatory are the lowest-powered, high-quality models that avoid the blue end of the spectrum. These are usually labeled as “non-fluorescent” or “energy efficient.” For astronomical observatories, shielded, low-pressure sodium lights work best because they contain less of the blue light that our observing instruments cannot handle.