Milky Way from Voyageur’s National Park (via National Park Service)
Cook County, Minnesota is holding its annual Dark Sky Festival this weekend. The county boasts the darkest night skies in Minnesota and indeed the entire eastern U.S.
In 2020, the nearby Boundary Waters Canoe Area Wilderness was designated an International Dark Sky Sanctuary by the International Dark-Sky Association. Cook County wants to capitalize on that recognition by inviting tourists to experience the night in a way that isn’t possible from the light-polluted population centers where most of us live.
This map, for instance, shows the intensity of light pollution across the state. It’s derived from a 2016 study that used both satellite and ground-based measures of nighttime brightness.
Areas colored black and gray are untouched or only minimally affected by artificial light at night. The only places in the state to experience those near-primordial skies are in the far northern tier, in a region running from Beltrami Island State Forest in the northwest through the Boundary Waters region near Grand Marais.
But wherever there are towns and people, there are lights. The smallest cities create relatively tiny, isolated light domes. But as towns get bigger and closer together those domes all merge together, creating uninterrupted tracts of light polluted skies.
Medium blue on the color scale marks the threshold for what the International Astronomical Union considers light polluted. By the time you get into the reds and oranges, the Milky Way is no longer visible even in the summer when it’s at its brightest. And people living in the white and pinkish areas, which include the core Twin Cities metro, effectively never experience true nighttime darkness. Skies in those places are effectively bathed in an artificial twilight all night long.
Light pollution doesn’t just ruin star gazing, however. It wreaks havoc on ecosystems, disorienting birds and insects and other creatures adapted to life under dark skies. Too much artificial light at night also interrupts human circadian rhythms, which may have ripple effects on everything from cancer incidence to preterm births.
Plus, light pollution is wasteful from a purely economic perspective – poorly designed fixtures that direct light away from the ground and up toward the sky cause billions in excess energy costs each year, according to the International Dark-Sky Association. For an explanation of how that works, check out this adorably earnest video from the rangers at Theodore Roosevelt National Park in North Dakota.
Practically speaking, here’s an illustration of what differences between polluted and non-polluted skies might look like to the naked eye. On the left, a simulation of the night sky in Minneapolis this evening at about 10 PM, looking to the northwest. On the right, that same swath of sky at the same time, except seen from the Boundary Waters wilderness. In the former, just a few pinprick stars are visible. The latter, on the other hand, shows a tapestry of twinkling lights suspended among the delicate structures of the winter Milky Way.
People who’ve seen night skies like this tend not to forget it, and they often find it’s something they want to experience again. That’s what places like Cook County are hoping to capitalize on – that the night sky itself can become a tourist draw just like any other natural resource, like a lake or a mountain or a park.
One word of warning, however, to people thinking of making the trip up there this weekend: The forecast calls for lots of clouds. But festival organizers promise they’ve got plenty of activities to keep people busy.
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