AAS Resolution on Light Pollution

Adopted 4 January 2017, Revised 7 June 2025

Astronomy has benefited from dark skies for thousands of years, but now the rapid growth of artificial sky glow – as fast as 10% per year – is jeopardizing all of humanity’s ability to see, study, and enjoy the cosmos from the Earth’s surface. More than half of all major observatories worldwide now operate under skies that are significantly brighter than natural darkness. Abundant scientific research demonstrates that light pollution also disrupts natural ecosystems, harms human health, and wastes energy.

To realize its mission to enhance and share humanity's scientific understanding of the universe as a diverse and inclusive astronomical community, the AAS calls on its members to enact the following lighting principles locally, regionally, and nationally in support of the protection and restoration of dark skies. Artificial light at night should be:

Useful: Start with natural darkness and add light only if needed. Areas around observatories should be kept naturally dark.

Targeted: Use shielding to target the direction of light so that it points downward and does not spill beyond where it is needed. Glare should be minimized.

Low Level: Light should be no brighter than necessary. Use the lowest light level that will serve the intended purpose.

Controlled: Use controls such as timers or motion detectors to ensure that light is available only when it is needed, dimmed when possible, and turned off when not needed.

Warm-colored: Limit shorter wavelength (blue-violet) light to the least amount needed. When light is needed near major observatories and sensitive natural sites, it should be monochromatic and long wavelength.

In conjunction with this call to action, which is aligned with DarkSky International / Illuminating Engineering Society’s joint statement, "Five Principles for Responsible Outdoor Lighting,” the AAS endorses:

  • IAU 2009 Resolution B5 "In Defence of the Night Sky and the Right to Starlight," affirming that access to a dark night sky is a universal human right, making quality outdoor lighting a worldwide imperative;
  • the American Medical Association's CSAPH Report 2-A-16 (May 2016) on "Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting";
  • the United Nations Office of Outer Space Affairs / IAU Dark & Quiet Skies I and II reports and recommendations (2020, 2022) for stopping and reversing the growth of light pollution and artificial sky glow; and
  • the United Nations Environment Programme / International Union for the Conservation of Nature’s report, “The World at Night: preserving natural darkness for heritage conservation and night sky appreciation” (2024).