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
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 four Virginia state parks have gained recognition as an International Dark Sky Park:4
Staunton River State Park - 2015
James River State Park - 2019 Sky Meadows State Park - 2021
Natural Bridge State Park - 2021
Shenandoah National Park offers an annual Night Sky Festival
Source: NASA, Night Sky
To get designated, at Natural Bridge State Park the lights pointed upward to illuminate the bridge all night were realigned. The Rockbridge County Board of Supervisors and the Lexington City Council both supported the designation, and will need to 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
Source: Tim Wallace, Descartes Labs, National Atlas (using nighttime data from the National Oceanic and Atmospheric Administration)
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
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)