Controlling Light Pollution

The effects of light pollution on a pristine night sky, with the Bortle scale shown at the bottom.
Image credit: NOIRLab/NSF/AURA, P. Marenfeld

Quick Links

Introduction

For many people, the greatest joy in astronomy comes from simply standing beneath a clear, dark night sky and marvelling at the heavens. Today, however, a growing majority of people can no longer see the true beauty of the night sky from their homes. Even some of the brightest stars are lost in the glare of light pollution from our towns, cities, roads and urban areas. For many people, the sight of the Milky Way stretching across the night sky is a childhood memory; sadly, today, a new generation is growing up that has never seen our own galaxy, the place we call home in the Universe. (e.g., Falci et al., 2016)

Though there is no set definition of light pollution, one that astronomers generally use is: any adverse consequence or impact of artificial light at night. The most obvious everyday manifestation of light pollution is in the increasing illumination of our night sky and the subsequent difficulties in observing astronomical objects from polluted locations (e.g., Green et al., 2022). Light from poorly designed, incorrectly directed light fixtures shines into the sky. There, it is scattered by air molecules, moisture and aerosols in the atmosphere causing the night sky to take on an often bright orange appearance, a phenomenon known as “sky-glow” (e.g., Hänel et al., 2018; Barentine, 2022).

Impacts of Light Pollution

The problem of light pollution is not only a menace to astronomers. People who have no interest in astronomy are affected by the intrusion of light into their properties, be it a street lamp that shines into their bedroom or the danger caused to motorists by the glare from poorly designed or placed streetlights and floodlights. Light pollution has numerous direct impacts on the environment (e.g., Gaston & Sánchez de Miguel, 2022; Gaston, Gardner, & Cox, 2023). Not only do lights consume a substantial amount of energy (e.g., Sánchez de Miguel et al., 2021), but the strain on wildlife in both urban and rural locations is great (e.g., Longcore & Rich, 2004). Light pollution is also an unnecessary waste of energy that eventually gets translated into a great and unnecessary cost to economies worldwide (e.g., International Dark-Sky Association, 2016).

Humans, too, are impacted by light pollution. The day-night cycles that are typically regulated by sunlight get interrupted, thereby suppressing the melatonin levels in our brains and making it more difficult to fall asleep (e.g., Touitou, Reinberg, & Touitou, 2017). Though LED lights were meant to be efficient light alternatives to incandescent bulbs, many health officials have actually expressed concern over the widespread use of white/blue LEDs (e.g., Ticleanu & Littlefair, 2015). Light pollution is also having a devastating impact on Indigenous communities who view the night sky as a vital part of their cultural identity (e.g., Hamacher, de Napoli, Mott, 2020).

Light pollution and other such electromagnetic interference (from radio waves, for example) have an outsized effect on astrophotographers, amateur astronomers, and professional astronomers alike. Today, several bodies within the International Astronomical Union attend to protecting our dark skies.

IAU and Dark Sky Protection

For example, Commission B7 works to protect existing and potential observatory sites from pollution at all wavelengths of the electromagnetic spectrum. With this in mind, Commission B7 works to preserve (and seeks to defend) important dark sky sites around the world. These include the professional observatories of Hawai‘i, continental Spain, the Canary Islands, North America, South Africa, Chile and Australia.

Some of the Commission’s members are also involved with scientific projects such as monitoring and modelling light pollution (e.g., Sánchez de Miguel et al., 2017). Recent research from a citizen science project shows that the issue of light pollution is only getting worse. If we, as a global society, do nothing to change our behaviour, light pollution will increase at an average rate of almost 10% each year (Kyba et al., 2023).

Alongside other international organisations, the International Astronomical Union (IAU) participated in the Starlight Declaration of 2007, which positioned the act of experiencing a dark night sky as “a fundamental socio-cultural and environmental right” and recognised the importance of awareness and spreading public knowledge about the issue of light pollution (2007). The IAU Resolution B5 of 2009 resolved to encourage its membership to raise awareness of and attempt to abate light pollution at local, regional, national, or international levels (IAU, 2009). More recently, the IAU, the UN Office of Outer Space Affairs, and the Government of Spain organised two workshops in 2020 and 2021, Dark and Quiet Skies I and II, which addressed light pollution and its link to cultural heritage, dark sky oases, astrotourism, and the bio-environment (Walker & Benvenuti, 2021; Dark Sky Oases Working Group et al., 2022).

International Efforts

Beyond the IAU, there are many organisations aiming to combat light pollution on an international and national scale. This includes:

International
- DarkSky International (formerly International Dark-sky Association; and all their regional offices)
- UN Office for Outer Space Affairs (UNOOSA)
- UNESCO’s International Day of Light
- Globe at Night (and all their partners)
- Starlight Foundation
- European Southern Observatory
National
- Australia: Australian Dark Sky Alliance
- Chile: Oficina de Protección de la Calidad del Cielo del Norte de Chile
- France: Association Nationale pour la Protection du Ciel et de l’Environnement Nocturnes
- Ireland: Dark Sky Ireland
- Italy: CieloBuio
- Japan: NAOJ Spectrum Management Office
- Morocco: Atlas Dark Sky
- Nigeria: Nigerian Conservation Foundation
- Serbia: Carpe Noctem
- Slovakia: Slovenská astronomická spoločnosť
- Spain: Cities at Night
- Switzerland: Dark-Sky Switzerland
- United States of America: Light Justice

… and many more.

Take Action

For problems as widespread as light pollution, it can seem as though there’s nothing for the ordinary person to do. However, you have more power than you think.

Tips for fighting light pollution:

Consider DarkSky International's Five Principles for Responsible Outdoor Lighting when deciding when, where and how to light outdoor spaces.
Change the lightbulbs in your home from blue LEDs to warm (less than 3000K LEDs). These are more energy efficient and cost-effective in the long run.
Avoid using floodlights outside your home, and endeavour to position all outdoor lights to only illuminate the intended space (e.g., shield the lights to only point downward and not into your neighbours’ yards).
Make sure to only use lights in your home and outside your home when you need them. If possible, use a motion sensor with outdoor lighting and/or a timer with indoor and outdoor lighting.
Ensure that the amount of light used for a particular application is appropriate to the task and is neither too little nor too much so as to ensure safety.
Perhaps the best way to understand why the dark night sky is so important is to experience it to its fullest extent for yourself. Try searching for a local astronomy club, planetarium, or astrotourism group that will show you a true dark sky.
If there are no astrotourism guides, observatories, or astronomy clubs near you, try organising something yourself by hosting a star party in a dark part of your community to highlight the beauty and importance of dark skies.
Start a conversation about light pollution in your community to raise awareness and educate your neighbours on the ill effects of light pollution.
Sign the Dark and Quiet Sky Protector Pledge and make your commitment to fighting light pollution today.
Petition your local lawmakers and community leaders to take a stance on light pollution using the email template we provide after signing the Pledge.

IAU OAO – Kainaat Cosmic Gup Shup

How Serious is the Problem of Light Pollution?

Watch the video below for more perspectives on light pollution.

Acknowledgements

We thank John Barentine for his generous contributions to the article and IAU Director of Communications Lars Christensen for authoring the article on which this was based. We also thank Kainaat Studios for their collaboration on the video.

References

Barentine, J. C. (2022). Night sky brightness measurement, quality assessment and monitoring. Nature Astronomy, 6(10), pp.1120–1132. https://doi.org/10.1038/s41550-022-01756-2

Dark Sky Oases Working Group, Optical Astronomy Working Group, Bioenvironment Working Group, Satellite Constellation Working Group, & Radio Astronomy Working Group. (2022). Dark and Quiet Skies for Science and Society: Report and recommendations. Zenodo. https://doi.org/10.5281/zenodo.5898785

Falchi, F., Cinzano, P., Duriscoe, D., Kyba, C. C. M., Elvidge, C. D., Baugh, K., Portnov, B. A., Rybnikova, N. A., & Furgoni, R. (2016). The new world atlas of artificial night sky brightness. Science Advances, 2(6). https://doi.org/10.1126/sciadv.1600377

Gaston, K. J., Gardner, A. S., & Cox, D. T. C. (2023). Anthropogenic changes to the nighttime environment. BioScience, 73(4), pp. 280–290. https://doi.org/10.1093/biosci/biad017

Gaston, K. J., & Sánchez de Miguel, A. (2022). Environmental Impacts of Artificial Light at Night. Annual Review of Environment and Resources, 47(1), pp. 373–398. https://doi.org/10.1146/annurev-environ-112420-014438

Green, R. F., Luginbuhl, C. B., Wainscoat, R. J., & Duriscoe, D. (2022). The growing threat of light pollution to ground-based observatories. The Astronomy and Astrophysics Review, 30(1). https://doi.org/10.1007/s00159-021-00138-3

Hamacher, D., de Napoli, K., & Mott, B. (2020). Whitening the Sky: light pollution as a form of cultural genocide, arXiv preprint. https://doi.org/10.48550/arXiv.2001.11527

Hänel, A., Posch, T., Ribas, S. J., Aubé, M., Duriscoe, D., Jechow, A., Kollath, Z., Lolkema, D. E., Moore, C., Schmidt, N., Spoelstra, H., Wuchterl, G., & Kyba, C. C. M. (2018). Measuring night sky brightness: methods and challenges. Journal of Quantitative Spectroscopy and Radiative Transfer, 205, pp. 278–290. https://doi.org/10.1016/j.jqsrt.2017.09.008

International Astronomical Union (2009). Resolutions of the XXVIIth IAU General Assembly. https://www.iau.org/static/resolutions/IAU2009_English.pdf

International Dark-Sky Association. (2016). Light Pollution Wastes Energy and Money. International Dark-Sky Association. https://www.darksky.org/light-pollution/energy-waste/

Kyba, C. C. M., Altıntaş, Y. Ö., Walker, C. E. & Newhouse, M. (2023). Citizen scientists report global rapid reductions in the visibility of stars from 2011 to 2022. Science, 379, pp. 265–268. https://doi.org/10.1126/science.abq7781

Longcore, T. and Rich, C. (2004), Ecological light pollution. Frontiers in Ecology and the Environment, 2, pp. 191–198. https://doi.org/10.1890/1540-9295(2004)002[0191:ELP]2.0.CO;2

Sánchez de Miguel, A., Aubé, M., Zamorano, J., Kocifaj, M., Roby, J., & Tapia, C. (2017). Sky quality meter measurements in a colour-changing world, Monthly Notices of the Royal Astronomical Society, 467(3), pp. 2966–2979. https://doi.org/10.1093/mnras/stx145

Sánchez de Miguel, A., Bennie, J., Rosenfeld, E., Dzurjak, S., & Gaston, K. J. (2021). First Estimation of Global Trends in Nocturnal Power Emissions Reveals Acceleration of Light Pollution. Remote Sensing, 13(16). https://doi.org/10.3390/rs13163311

Starlight. (2007). Declaration in defence of the night sky and the right to starlight. Starlight. https://starlight2007.net/index_option_com_content_view_article_id_185_starlight-declaration_catid_62_the-initiative_itemid_80_lang_en.html

Ticleanu, C., & Littlefair, P. (2015). A summary of LED lighting impacts on health. International Journal of Sustainable Lighting, 1(1). https://doi.org/10.26607/ijsl.v17i0.11

Touitou, Y., Reinberg, A., & Touitou, D. (2017). Association between light at night, melatonin secretion, sleep deprivation, and the internal clock: Health impacts and mechanisms of circadian disruption. Life Sciences, 173, pp. 94–106. https://doi.org/10.1016/j.lfs.2017.02.008

Walker, C. & Benvenuti, P. (Eds.). (2022). Dark and Quiet Skies II working group reports. Zenodo. https://doi.org/10.5281/zenodo.5874725