Causes of Light Pollution
Light pollution is the biggest menace faced by astronomers. Like all types of pollution, light pollution is man-made. With light pollution, the light from artificial sources like street lights, vehicles, buildings, airports and many other sources illuminates the sky in such a way that the faint astronomical objects like stars, shooting stars, galaxies etc, become invisible to the observers on Earth. Most of these artificial sources are poorly designed so that the light from these sources is directed toward the sky. These light rays are then scattered by the microscopic particles in the atmosphere. The air pollution has increased the density of particulate materials like dust, smoke and soot. Besides that, the air molecules and water vapor droplets are present everywhere. The scattering of light by these cause sky glow and glare, thus making it impossible to observe the faint stars with naked eye. As the sky becomes more and more illuminated, the visibility of dimmer objects in the sky like fainter stars, diffuse galaxies and nebula diminishes considerably.
In addition to the decreased visibility, light pollution is causing another problem for astronomers. Usually, astronomers rely on the spectra of astronomical objects to study their constituents, and the speed with which it is approaching or receding from our galaxy. Each line in the spectrum signifies an element present in the astronomical object under study. Hence, these spectra are powerful tools in the hands of astronomers. But, the light from artificial sources interferes with spectra, making it difficult to distinguish between the spectral lines by the astronomical object and those from artificial sources. These problems force astronomers to depend on more and more advanced telescopes to observe the night sky or space based instruments.