2022-12-06 08:00:00
If you were to look up at the night sky, it could vary from a dusty glow to an inky black expanse with thousands of sparkling stars, depending on where you are.
on a clear night, estimates suggest A few thousand stars are visible to the naked eye, but the light pollution glare of city and small town lights prevents us from getting a view of the cosmos in all its glory.
To describe how much light pollution a particular location has, astronomers use the Bortle scale, which ranks visibility from level one to nine. John Bortle first described it in a 2001 issue of Sky & Telescope, an astronomy magazine.
Each level classifies the night sky based on their cosmic views. You can find the Bortle scale level for your night sky using the interactive map tool at lightpollutionmap.info.
These images show how much more stars you can see in really dark skies, outside of cities, suburbs and other human light sources:
Level nine classifies downtown, the worst for stargazing. (Tony Flanders)
What is observable: the Moonnearest planets, and a handful of the brightest stars
Where to find it in the US: New York, Las Vegas, Los Angeles
A sky with extremely bright light pollution, mostly found over large cities, glows orange. Although it may not be as potentially harmful as other types of pollution, light pollution can affect human health.
Multiple studies have indicated that exposure to light at night can disrupts the body’s biological clockwhat is linked to health complicationsinclusive obesity, depressionand sleep disorders.
Level eight classifies city skies, where you may only see faint constellations. (Sriram Murali)
What is observable: Constellations may be slightly visible
Where to find it in the US: Boston, Massachusetts; Austin, Texas; Indianapolis, Indiana
At level eight, the sky could be so clear from light pollution that you could read through it. Most stars and even constellations will be invisible to the naked eye.
Level seven classifies the transition from urban to suburban areas, the third worst for stargazing. (Sriram Murali)
What is observable: star cluster M44 and the Andromeda galaxy is very indistinct, and the Milky Way is totally invisible or nearly so
Where to find it in the US: Seattle, Washington; Savannah, Georgia; Salt Lake City, Utah
The light pollution in these areas makes the entire sky appear pale gray in color, and the Milky Way is effectively invisible.
A 2016 study estimated that even on the clearest night, one third of humanity cannot see the milky way.
Level six classifies clear suburban skies where some stars are visible. (Tony Flanders)
What is observable: the Andromeda galaxy is only faintly visible
Where to find it in the US: Albuquerque, New Mexico; Lincoln, Nebraska; Bloomington, Indiana
At level six, clouds appear quite clear and the sky glows a greyish white. Light pollution under these conditions is very bright.
Level five classifies suburban airspace where you may faintly see the Milky Way. (Sriram Murali)
What is observable: the Milky Way galaxy can look washed out
Where to find it in the US: Burlington, Vermont; Santa Fe, New Mexico; Grand Junction, Colorado
Most of us spend our lives in this Bortle scale level or higher, according to Telescope Shop OPT Telescopes.
At level five, light pollution will be visible in most, if not all, directions. Clouds are brighter than the sky itself, and the Milky Way is faint.
Level four classifies the transition from suburban to rural areas, where you can see the Milky Way. (Sriram Murali)
What is observable: the Milky Way, the Triangle Galaxy
Where to find it in the US: Twin Falls, Idaho; Flagstaff, Arizona; Wind River Indian Reservation, Wyoming
Light pollution is visible in various directions. Under this sky, the sky background begins to appear gray instead of black.
Level three classifies rural skies where you can see the dusty Milky Way. (Sriram Murali)
What is observable: the Milky Way Galaxy, and densely packed collections of stars such as M4, M5, M15and M22
Where to find it in the US: Yosemite National Park, California; Everglades National Park, Florida; Great Smoky Mountains National Park, Tennessee
You can see the Milky Way, but the fine detail is gone. Some clouds lighten in the direction of light sources, but overhead clouds remain dark.
Level two classifies typical dark-sky sites, the second best for viewing the cosmos. (Sriram Murali)
What is observable: the Milky Way Galaxy, the Magellanic Clouds
Where to find it in the US: Cherry Springs State Park, Pennsylvania; Adirondack Park, New York; Joshua Tree National Park, California
The Milky Way is highly visible to the naked human eye. Heaven glowsa haze of light from scattered light sources on the ground, may be faintly visible along the horizon.
Level one classifies prime dark-sky sites, best for stargazing. (Sriram Murali)
What is observable: the Milky Way Galaxy, the Andromeda Galaxy, the Orion Nebula
Where to find it in the US: Big Bend National Park, Texas; Grand Canyon National Park, Arizona; Denali National Park, Alaska
Level One skies offer an unobstructed view of the cosmos, comparable to that seen by Galileo. The night sky is full of stars, making it more difficult to analyze faint constellations. The Milky Way is so bright that it is capable of casting shadows.
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