Light Pollution and Dark Skies in Virginia

satellite image of lights at night
Source: Defense Meteorological Satellite Program, Global City Lights

As the population of Virginia increases, artificial illumination at night expands and spoils the view of the stars and planets.

In many cases, mercury vapor security lights are placed on a pole near the house in isolated valleys. In urban settings, lights on streets, in shopping centers, and across developments create an environment in which children are never exposed to the constellations. Only during major power failures (blackouts) do residents in urbanized areas get to see the Big Dipper or Orion. According to the National Park Service:1

...roughly 80% of people in North America cannot see the Milky Way due to electric lights at night. In other words, our dark night skies often really aren't all that dark.

night lights of Virginia, showing concentrations of human settlement
night lights of Virginia, showing concentrations of human settlement
Source: National Atlas

Star visibility can be measured by identifying the magnitude of the faintest stars that are visible. People with excellent visual acuity might spot 8.0 magnitude stars, without a telescope, in a place with no artificial light intrusion. In an urban setting, stars with a magnitude beyond 4.0 are rarely visible.

The Bortle Dark-Sky Scale provides nine categories based on the overall brightness of the sky and the visibility of objects such as nebulae and galaxies. Under the best Class 1 conditions ("observer's Nirvana!"), the galaxy M33 is an obvious naked-eye object. In a Class 9 inner-city sky, no Messier objects are visible to the unaided eye except perhaps the Pleiades.2

Shenandoah National Park started an annual Dark Sky Festival in 2016, to interpret a natural resource about which many visitors were unfamiliar. The National Park Service later partnered with the Illuminating Engineering Society (IES) to develop lighting standards and best practices so future construction projects in units of the National Park System would be "night sky friendly."3

Sky Meadows State Park has recognized that it has a natural asset valued by Northern Virginians - a dark sky where stars are visible. The state park sponsors special astronomy programs, and offers a perspective on the natural world just as valuable as hikes along the Appalachian Trail. It is one of five Virginia parks have gained recognition as an International Dark Sky Park:4

Shenandoah National Park offers an annual Night Sky Festival
Shenandoah National Park offers an annual Night Sky Festival
Source: NASA, Night Sky

To achieve designation, Natural Bridge State Park realigned the lights that were pointed upward to illuminate the bridge all night. The Rockbridge County Board of Supervisors and the Lexington City Council both supported the designation, and indicated they would prevent new light pollution near the park so it can retain the designation. Some communities away from state parks, such as Charlottesville, also are implementing "dark sky" ordinances that require shields on lights so the illumination is directed towards the ground.

amount of light emitted per person in Virginia
amount of light emitted per person in Virginia
Source: Tim Wallace, Descartes Labs, National Atlas (using nighttime data from the National Oceanic and Atmospheric Administration)

Even in urbanized Fairfax County, there was an opportunity to create a dark sky park. In October 202, the Fairfax County Park Authority nominated Observatory Park at Turner Farm in Great Falls for "dark sky" designation by the International Dark Sky Association.5

Fairfax County Park Authority sought dark sky designation in 2021 for Observatory Park (red X), about six miles northwest from Tysons
Fairfax County Park Authority sought dark sky designation in 2021 for Observatory Park (red X), about six miles northwest from Tysons
Source: ESRI, ArcGIS Online

Links

lights of Norfolk (southeast corner), Richmond, and Northern Virginia reveal the crescent of dense population in Virginia
lights of Norfolk (southeast corner), Richmond, and Northern Virginia reveal the crescent of dense population in Virginia (Lynchburg is circled in red, Charlottesville in yellow)
Source: NASA, Earth's City Lights

References

1. "Night Sky," Shenandoah National Park, National Park Service, https://www.nps.gov/shen/learn/nature/nightsky.htm (last checked February 15, 2020)
2. "Introducing the Bortle Dark-Sky Scale," Sky and Telescope, February 2001, https://www.skyandtelescope.com/astronomy-resources/light-pollution-and-astronomy-the-bortle-dark-sky-scale/ (last checked February 15, 2020)
3. "Night Sky Festival," Shenandoah National Park, National Park Service, https://www.nps.gov/shen/planyourvisit/night-sky-festival.htm; "National Park Service Partners with Illuminating Engineering Society," National Park Service, https://www.nps.gov/orgs/1207/04-06-21-nps-partners-with-illuminating-engineering-society.htm (last checked April 13, 2021)
4. "The sky above Natural Bridge State Park is now dark - officially," Richmond Times-Dispatch, April 7, 2021, https://richmond.com/news/state-and-regional/the-sky-above-natural-bridge-state-park-is-now-dark-officially/article_c7217093-73fd-57b6-a63d-aec0677a67cc.html; "Virginia's newest dark sky park opens Oct. 7," Cardinal News, September 29, 2021, https://cardinalnews.org/2021/09/29/virginias-newest-dark-sky-park-opens-oct-7/ (last checked September 30, 2021)
5. "Fairfax officials seek 'dark-sky' status for park in Great Falls," InsideNOVA, October 10, 2021, https://www.insidenova.com/news/fairfax/fairfax-officials-seek-dark-sky-status-for-park-in-great-falls/article_64225114-293e-11ec-a22d-5b270b9de817.html (last checked October 11, 2021)

light pollution is one of the most pervasive forms of environmental alteration
light pollution is one of the most pervasive forms of environmental alteration
Source: Fabio Falchi et al., Science Advances, The new world atlas of artificial night sky brightness (June 10, 2016)


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