The night sky is a wonderful sight, with thousands of stars, many different constellations and the misty haze of the Milky Way galaxy glowing in the vast skies above. However, experiencing such a great view of the night sky depends on one crucial factor – that no light is present to obscure any of the stars.
Aside from moonlight and the setting and rising sun, most nocturnal light is produced from human-generated sources, and often drowns out many of the stars in the night sky, including the entirety of the Milky Way.
Although urban centers make viewing the Milky Way virtually impossible, wilderness areas and national parks, particularly across the geography of the western half of the United States, are ideal for stargazing.
Light Pollution is Obstructing Star Viewing
Patches of natural dark sky over the United States are shrinking over time due to human impacts such as urbanization, but some steps are being taken to reduce this.
Despite the fact that the lightbulb has greatly enhanced our lives, there have been some drawbacks.
Almost 80% of Americans are Unable to See the Milky Way Where They Live
One of these is that levels of light pollution have massively increased across vast swathes of the United States, where light generated from numerous sources, in particular street lamps, homes, offices and traffic, have significantly reduced the visibility of the night sky. Related: How Light Pollution Affects People and the Environment
A 2016 study by an international team of scientists and researchers complied a world atlas of the intensity of light pollution across the world.
The study found that almost half of the land mass of the United States is located beneath skies that are affected by noticeable levels of light pollution, with only pockets of the USA located beneath true dark skies, where no measurable light pollution exists at all.
A staggering 99% of the American population lives underneath light polluted skies, meaning that the vast majority of Americans do not see a completely natural view of the night sky.
Light pollution varies in intensity across different parts of the United States.
Although it is most intense over cities and other large urban areas, small but noticeable levels of light pollution are also visible over many rural or semi-rural parts of the United States.
The 2016 study found that in the large urban centers, viewing the Milky Way is virtually impossible with the naked eye, making it pretty much invisible to almost 80% of Americans.
Even in rural areas close to cities, much of the natural night sky is drowned out by light from nearby urban areas – although the Milky Way may be slightly visible in these places, it is still difficult to see it in its full detail without a telescope.
Light Pollution Affects Natural Parks
Light pollution can also affect the night sky some distance away from urban centers – for example, the sky above Death Valley National Park is impacted with light from Los Angeles and Las Vegas, both of which are located over a hundred miles away.
This shows just how extensive the effects of light pollution can be, with the potential to impede views of the stars – and of the Milky Way – some distance away from large cities, even in remote and unpopulated areas.
This also proves how problematic urban expansion is in terms of threatening rural dark skies; as cities expand outward, which is occurring at a large rate in the United States, light-emitting streetlamps and buildings expand with them.
There are only a few patches of completely dark sky left in the United States, the largest of which are southeast Oregon, western Utah and northern Arizona – however, these are being encroached upon by the rapid expansion of cities such as Las Vegas and Phoenix.
Why are National Parks Ideal for Viewing the Milky Way?
Many national parks are ideal locations for viewing the Milky Way.
One of the main reasons for this is that they often cover wild and remote areas, and many are located at least a hundred miles away from urban centers – the only nearby settlements are often small towns and villages, which do not emit great quantities of light.
National Parks are protected areas, meaning that all building activity within the parks is strictly regulated, which prevents urbanization and the introduction of large freeways within their boundaries. Thus, very little light pollution is produced around, and within, many of the United States’ national parks – this makes it easy to view every single star in the night sky, which often includes the entirety of the Milky Way in full detail.
What is an International Dark Sky Park?
Many national parks are recognised as an International Dark Sky Park (IDSP) by a non-profit organization known as the International Dark-Sky Association, which campaigns to protect the night sky from light pollution.
IDSPs are certified areas of land that possess an exceptional quality of clear night skies, and work to maintain a great nocturnal environment. They take steps to reduce light sources in the park, and to educate and inform visitors of their aims, and the importance of reducing light pollution in general. Related: Niue Designated the First Dark Sky Nation
For example, the Black Canyon of the Gunnison National Park in Colorado is a recognized IDSP – it only uses artificial lighting if it is absolutely necessary, which is often for safety purposes.
Also, motion detectors are used to only switch lights on when a building, or a small and specific area of the national park, is being used. All outdoor lighting uses low-energy, low-impact bulbs that direct light to the ground, and does not scatter it in all directions.
Which US National Parks Provide the Best Views of the Milky Way?
Any national park located a good distance away from an urban area is ideal for seeing the Milky Way.
Many of these are located in the western half of the United States, from Arizona up to Montana and Idaho, as far east as the Rockies, and at least two hundred miles away from the populated cities along the west Coast.
The desert areas of Arizona, Utah and Nevada are particularly ideal due to the incredibly low population of these parts of the United States, and for their high frequency of cloudless night skies.
Great Western Starry Way
Fortunately, a large number of US national parks are spread out across this area, and have been named The Great Western Starry Way.
Many of the US national parks have been certified as International Dark Sky Parks (IDSPs), the majority of which are located in the area identified in the last paragraph, and provide particularly spectacular views of the night sky.
Viewing the Milky in Canyonlands National Park
The Canyonlands National Park, located in south-eastern Utah, is a superb stargazing location. Its remote desert location means that any light pollution is very slight, with a lack of farms or ranches close to the park; only small towns are located within a 100-mile radius of Canyonlands, and the nearest large city is situated more than 200 miles away.
Therefore, the Milky Way is visible with incredible detail.
Viewing the Milky Way in Great Basin National Park
The Great Basin National Park is also great for stargazing. Located in eastern Nevada, it is a long distance from the nearest large city, and is surrounded by vast areas of open and sparsely-populated land.
Much of the park reaches an altitude of more than 8,000 feet above sea level, with its highest peaks maxing out at above 11,000 feet. This means that the national park is above any minimal light pollution from below, which struggles to reach this high up, but that there is less atmosphere above the surface of the Great Basin than there is in many other US national parks.
As a result, the stars in Great Basin National Park appear clearer than in lower-altitude parks.
Viewing the Milky Way in Bryce Canyon National Park
However, Bryce Canyon, another certified IDSP, is perhaps the most ideal national park for observing the night sky.
Located in southern Utah, it is placed right in the heart of the United States’ dark sky area, with a low number of settlements in the surrounding area, and a dry and often cloudless desert climate.
Like Great Basin National Park, Bryce Canyon also has a rather high altitude, topping out at 8,000 feet above sea level. On a clear and moonless night, thousands of stars can be seen, with the Milky Way crossing the night sky from horizon to horizon.
Milky Way Seasonality
The northern hemisphere sees the Milky Way begin to rise from the south during the spring. Therefore, all of the US national parks begin to see the galactic core rise a few hours before sunrise, from as early as mid-March.
Much of the Milky Way is the most visible during the summer months, when its center is clearly visible as soon as the sun sets.
During the fall months, the galactic core becomes increasingly less visible, with its appearance increasingly limited to the early evening.
The core of the Milky Way is not visible in the northern hemisphere during the winter months.
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Astronomy & night sky programs – Bryce Canyon National Park. (n.d.). NPS.gov (U.S. National Park Service). https://www.nps.gov/brca/planyourvisit/astronomyprograms.htm
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Plumer, B. (2016, June 10). The night sky is vanishing: 80 percent of Americans can no longer see the Milky Way. Vox. https://www.vox.com/2016/6/10/11905390/light-pollution-night-sky