Helena Joyce
Light pollution is a growing problem for observatories around the world. A recent study found that three quarters of major observatories are affected by light pollution, with only seven out of 28 major sites considered to be uncontaminated. The problem is particularly acute in North America, but even observatories in South America are not immune. The Tokyo Atacama Observatory in Chile experiences strong light pollution, and a planned renewable energy project in the country could threaten the European Southern Observatory's Very Large Telescope, one of the world's most powerful sky-watching instruments. With light pollution levels continuing to rise, immediate action is needed to protect the future of ground-based astronomy.
| Characteristics | Values |
|---|---|
| Number of major observatories with light pollution | 21 out of 28 |
| Percentage of major observatories with light pollution | 75% |
| Number of observatories with light pollution below 1% threshold | 7 |
| Number of observatories with light pollution below 1% threshold at 30 degrees above the horizon | 1 |
| Maximum allowable artificial brightness threshold for major observatories | 10% |
| Number of observatories that exceed the 10% threshold | 2/3 |
| Worst light pollution in US cities | Charlotte, North Carolina; Detroit, Michigan; Washington, D.C. |
| Cities with the best conditions for stargazing | New Orleans, Louisiana; Denver, Colorado; Phoenix, Arizona; Chicago, Illinois; New York City, New York |
| Worst light pollution in observatories | Tokyo Atacama Observatory (TAO) in Chile; Paranal Observatory in Chile |
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What You'll Learn
Light pollution is spreading to previously dark skies
Light pollution is increasingly becoming a problem for observatories, with artificial light contaminating the night sky and impairing our view of the cosmos. A recent study published in the Monthly Notices of the Royal Astronomical Society found that three-quarters of major observatories are affected by light pollution, with only seven out of 28 major sites considered "uncontaminated". This is due to a variety of factors, including urban sprawl, industrial activities, and even light emitted from temporary workers' lodging near observatories.
One notable example is the Mt. Wilson Observatory in California, which was constructed in the early 1900s when it was far from the lights of Greater Los Angeles. Today, the LA area has a population of 18.6 million, and Mt. Wilson faces much more light pollution due to the urban development that has brought civilisation closer to the observatory. Similarly, the Kitt Peak National Observatory in Arizona, which was once far from the city of Tucson, now faces increased light pollution as the area's population has grown to one million.
Even observatories in darker, more secluded regions are not immune to light pollution. For instance, the Tokyo Atacama Observatory (TAO) in Chile experiences strong light pollution from the Atacama Large Millimeter/submillimeter Array, operated by radio astronomers. In addition, the Paranal Observatory, also in the Atacama Desert in Chile, is affected by light pollution from workers' lodging near the European Southern Observatory's under-construction Extremely Large Telescope.
The problem of light pollution is not limited to specific observatories but is spreading globally. The World Atlas of Artificial Sky Brightness shows that light pollution is strongest in the eastern half of North America, but it is also creeping up on observatories in the western half. South America, while having lower levels of light pollution overall, is not exempt, with observatories in northern Chile experiencing light pollution from industrial activities.
The impact of light pollution on astronomy is significant. It reduces the number of stars and galaxies that can be observed, impeding projects such as the Vera Rubin Observatory's mission to map the distribution of dark matter in the universe by collecting a sample of 2.6 billion galaxies. To address this issue, efforts must be made to decrease light pollution levels and protect the future of ground-based astronomy. This includes reducing outdoor lighting from buildings, roads, and advertising, which can interfere with the study of the universe by astronomers.
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Light pollution affects even remote observatories
Light pollution is a growing problem for observatories around the world, even those in remote locations. A recent study by researchers from Italy, Chile, and Spain examined light pollution levels at almost 50 observatories, ranging from large professional observatories to smaller amateur facilities. The results showed that only 7 out of 28 major observatories had light pollution levels below the expected natural sky brightness threshold of 1%. This means that the remaining 21 sites, or three-quarters of all major observatories, are considered contaminated by light pollution.
One of the most surprising findings of the study was the strong light pollution affecting the Tokyo Atacama Observatory (TAO) in Chile, which turned out to be caused by the nearby Atacama Large Millimeter/submillimeter Array. The Paranal Observatory, also located in the Atacama Desert in Chile, was found to have the darkest sky of all the observatories studied, despite temporary light pollution from workers' lodging near the under-construction Extremely Large Telescope.
Light pollution can have a significant impact on the ability of observatories to study the cosmos. For example, the Las Campanas Observatory in Chile is heavily affected by a single partially illuminated highway 40 km away. In addition, the European Southern Observatory's Very Large Telescope in the Atacama Desert, which is covered by strict national regulations protecting the dark sky, faces challenges due to light pollution from industrial activities such as open-pit mining and oil and gas facilities in the region.
Even remote observatories are not immune to light pollution. For instance, the Kitt Peak National Observatory in Arizona was constructed in the late 1950s far from the city of Tucson, but today the area's population has grown to 1 million, and the observatory faces much more light pollution. This urban influence hampers visibility for astronomical observations, as the glare from city lights scatters in the atmosphere.
To address the issue of light pollution, some regions have enacted laws to stop the spread of light pollution and secure unhindered views of the cosmos. However, these strategies do not appear to be particularly effective, and immediate action is needed to decrease the amount of contamination from artificial light. This includes implementing night-sky-friendly lighting fixtures and considering the overall average brightness across the sky, as well as how artificial light illuminates the ground.
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Light pollution is caused by human activities
Light pollution is a growing problem for observatories, with artificial light contaminating the night sky and impairing our view of the universe. Sources of light pollution include outdoor lighting for buildings, roads, advertising billboards, and industrial activities such as mining and oil and gas facilities. Even remote observatories are not immune, with light pollution spreading to previously dark sites.
A recent study by researchers from Italy, Chile, and Spain examined light pollution levels at almost 50 observatories worldwide, including both large professional observatories and smaller amateur facilities. The results showed that only 7 out of 28 major observatories had light pollution levels below the expected threshold of 1% of natural sky brightness. This means that the remaining 21 sites, or three-quarters of all major observatories, are considered contaminated by artificial light.
One surprising source of light pollution affecting the Tokyo Atacama Observatory (TAO) in Chile was found to be the Atacama Large Millimeter/submillimeter Array, operated by radio astronomers. Another observatory impacted by light pollution is the Kitt Peak National Observatory in Arizona, which was once far from the city of Tucson but now faces much brighter skies due to urban sprawl. Even telescopes in darker regions, such as northern Chile or western Texas, are not exempt from light pollution caused by industrial activities.
The problem of light pollution is not limited to observatories but also affects people's ability to stargaze and appreciate the night sky. Cities with high light pollution, such as Charlotte, North Carolina, and Detroit, Michigan, have radiance values that overwhelm the light from the stars. To combat light pollution, it is essential to reduce artificial lighting and protect dark skies, ensuring that both astronomers and the general public can continue to explore and discover the wonders of the universe.
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Light pollution is increasing at a rate of 10% per year
Light pollution is becoming an increasingly pressing issue, with the night sky brightening by an average of 9.6% to 10% each year. This is largely due to the proliferation of artificial lighting, which is having a detrimental effect on observatories around the world.
A recent study published in the Monthly Notices of the Royal Astronomical Society found that three-quarters of major observatories are affected by light pollution. This includes some of the world's largest professional observatories, as well as smaller amateur facilities. The study utilized a model of light propagation in the Earth's atmosphere, applying it to night-time satellite data to determine light pollution levels.
The impact of light pollution on observatories is significant, with only a handful of major observatories remaining below the 1% threshold for natural sky brightness. The majority of sites have light pollution levels above this limit, with two-thirds exceeding the more relaxed 10% limit set by the International Astronomical Union in the 1970s. This means that even at major observatories, the night sky is more polluted than previously assumed.
The sources of light pollution vary, with some unexpected contributors. For example, the active Kilauea volcano in Hawaii emits light at infrared wavelengths, but some of it spills into the visible range. Another example is the Tokyo Atacama Observatory in Chile, which is affected by light pollution from the Atacama Large Millimeter/submillimeter Array.
The increase in light pollution has serious implications for astronomy, the environment, and the health of both humans and wildlife. It is essential to take immediate action to reduce light pollution levels and protect the future of ground-based astronomy and the natural darkness of the night sky.
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Light pollution is worse in some cities than others
Light pollution is a growing problem for observatories around the world, with artificial light contaminating the night sky and impairing our view of the cosmos. A recent study found that three-quarters of major observatories are affected by light pollution, which is even encroaching on observatories in previously pristine locations. This is a concern for astronomers, who are finding it harder to study the universe due to the glare and noise of artificial light.
The impact of light pollution varies between cities and observatories, with some sites experiencing more severe contamination than others. For example, the Tokyo Atacama Observatory (TAO) in Chile suffers from strong light pollution, which, ironically, comes from the nearby Atacama Large Millimeter/submillimeter Array. In the United States, Charlotte, North Carolina, and Detroit, Michigan, are known for their high levels of light pollution, making them poor choices for stargazing.
On the other hand, some cities offer better conditions for astronomy enthusiasts. New Orleans, Louisiana, stands out for its low light pollution and high elevation, providing a clear view of the night sky. Denver, Colorado, boasts the highest elevation of all the cities analysed, at 5,280 feet, making it a prime location for stargazing.
The problem of light pollution is not limited to a single city or region but is a global issue. Even observatories in remote locations are not immune, with sites in northern Chile and western Texas experiencing light pollution from industrial activities. To address this issue, efforts must be made to reduce light pollution levels and protect the future of ground-based astronomy.
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Frequently asked questions
It is hard to say which single observatory experiences the worst light pollution, but a 2022 study found that 21 out of 28 major observatories were above the expected threshold of 1% of natural sky brightness.
The expected threshold is 1% of natural sky brightness, which means that anything above this level can be considered contaminated.
The zenith is the point in the sky directly above an observer. It is the darkest portion of the night sky and is, therefore, the least polluted by light.
Light pollution is caused by artificial light sources such as outdoor lighting for buildings, roads, and advertising. These light sources can add glare and noise to the night sky, reducing the number of visible stars and galaxies.
Light pollution can make it harder for astronomers to study the cosmos as it reduces the number of galaxies that can be reliably measured. It can also increase the total exposure time required to get the same results as in a darker sky.
