A recent study found that the night sky is getting brighter by about 10% every year and is wiping stars out of our view due to increased levels of light pollution.
The warning comes from astronomers who are monitoring an international citizen science project called Globe at Night that has been collecting visibility data for prominent constellations for more than a decade.
Scientists have said our change of heart is a loss to scientists who rely on dark skies to study the universe, and a loss to our “cultural heritage.”
Professor Chris Impey of the University of Arizona and Dr. Connie Walker of the National Research Laboratory for Optical and Infrared Astronomy explained: “For decades, astronomers have been building telescopes in the darkest places on Earth to avoid light pollution. Today, most people live in cities or suburbs that shed light. Excessive light in the night sky, which greatly reduces the visibility of the stars.
Satellite data show that light pollution in North America and Europe has remained stable or declined slightly over the past decade, while it has increased in other parts of the world such as Africa, Asia and South America.
However, the satellites transmit the blue light of LEDs that are commonly used for outdoor lighting, resulting in less light pollution.
The Globe at Night project is recruiting members of the public as “citizen scientists” to measure how people’s view of the sky is changing on a daily basis.
“By relying on citizen scientists, it’s very easy to take multiple measurements of the night sky over time from different locations,” said Empy and Dr. Walker.
To provide data for the project, volunteers enter the date, time, location, and local weather conditions into the online reporting page at any time about an hour after sunset on certain nights of each month. The page then displays eight panels, each showing a constellation visible at that time of year, such as Orion (or Gemini) in January and February.
The first panel, which is a brightened night sky, shows several brighter stars. Each panel shows gradually fading stars, representing a darker sky. Participants then match what they see in the sky with one of the panels.
The Globe at Night team launched the reporting page as an online application in 2011, when LED lighting began to become widespread.
In a recently published study, researchers looked at data collected since then, first filtering out potentially unreliable reports, such as those collected at dusk when the moon brightened the sky or when the sky was covered with clouds.
This left them with 51,000 data points, most of which were recorded in Europe and North America.
The team found that, on average, the night sky gets 9.6% brighter each year, meaning that the night sky now appears to many to be twice as bright as it was just eight years ago.
As Prof. Impey and Dr. Walker note, “If this trend continues, a child born today in a place where 250 stars are now appearing will only see 100 stars by their 18th birthday.”
The duo continued: “The main reason for the increase in the brightness of the night sky is urbanization and the increasing use of LEDs for outdoor lighting. The loss of dark skies due to light pollution, as well as the increase in the number of satellites orbiting the Earth, threatens our ability as astronomers to do science.”
They continued: “Light pollution also interferes with the diurnal cycle of light and dark that plants and animals use to regulate sleep, nutrition, and reproduction.”
However, there are steps people and their communities can take to reduce light pollution, such as protecting street lights to shine down, replacing white light with yellow alternatives, and setting lighting on timers or motion sensors.
The full results of the study are published in the journal Science.