The International Astronomical Union (IAU) welcomes involvement in the International Year of Light (IYL). Innovation in solid-state lighting solutions holds the potential for meeting the objectives that astronomers seek for quality outdoor lighting. The concern of astronomers to preserve access to the dark night sky is reinforced by complementary efforts to conserve energy, protect wildlife, and enhance human health.
Light pollution is artificial light that is not needed. Huge amounts of such stray light are still needlessly being sent upwards. Substantial amounts of this wasted light are then scattered and/or refracted back down to earth. This creates a luminous glow in the sky that competes with the faint light being studied by optical astronomers and that veils the natural beauty of the sky that everyone should be able to enjoy. LED fixtures with full cutoff shielding are currently being installed in many cities that can help avoid their light being sent unnecessarily upward, by preventing any light from radiating above horizontal.
Furthermore, until recently, astronomers have been able to observe blue light from the cosmos without much interference from the artificial light from humans, thanks mainly to the widespread use of (yellow) sodium lamps; much to the chagrin of astronomers, the low-pressure sodium lamps are becoming rare and difficult to maintain. The 2014 Nobel Prize for Physics was awarded for the work on GaN LEDs – that produce a strong component of blue light. The increasing interference from blue LED light is particularly difficult for accessing the night sky. Blue wavelengths also mediate day-night signaling in the human body and provide directional and other signals for wildlife; artificial glow in that color clearly adds biological complication, and possible risks to health. Promising developments in the production of energy-efficient narrow-band amber LEDs and blue cutoff LED fixtures offer hope for mitigation.
The solid-state technology supports two other goals of quality lighting – intensity matched to the density of development and timed control of the output. Outdoor signs and lights require much less luminous output in suburban and rural areas than in the midst of a mid-city commercial district. Similarly, advertising and decorative lighting have little impact when there is no traffic to see it, so lights can be quenched during the quiet night hours.
For the IAU’s Cosmic Light Working Group, the IYL is offering a welcome opportunity to build on the clear success of the “International Year of Astronomy” 2009 in the area of outreach and education. Thousands of schools around the world showed interest and ingenuity in responding to the educational needs of humanity, which had almost unconsciously been shutting itself inside a ball of light on a tiny planet. Humanity has the right to continue to learn from what the sky can tell us. It also has the skill to develop competitive, astronomy-friendly, LED lighting – and the option to deploy it to the benefit of all.