Star visibility rapidly eroding as night sky brightens: study

Star visibility rapidly eroding as night sky brightens: study

Rapidly growing light pollution -- skylight -- is making it harder to see stars in the night sky with the naked eye

Rapidly growing light pollution — skylight — is making it harder to see stars in the night sky with the naked eye.

Light pollution is growing rapidly and in some places the number of stars visible to the naked eye in the night sky is being reduced by more than half in less than 20 years, according to a study released on Thursday.

The researchers, whose results were published in the journal Sciencewho said that the increase in light pollution—skyglow—they found was much greater than that measured by satellite observations of the Earth at night.

To study the change in global sky brightness from artificial light, the researchers used stellar observations from 2011 to 2022 submitted by more than 51,000 “citizen scientists” around the world.

Participants in the “Globe at Night” project run by the US National Optical-Infrared Astronomy Research Laboratory were given star maps and asked to compare them to the night sky at their location.

The change in the number of visible stars reported was equivalent to a 9.6 percent annual increase in sky brightness, averaged over the participants’ locations, the researchers said.

Over a period of 18 years, given such a change in star brightness, that number would be reduced to 100 in a location where 250 stars are visible.

Credit: NOIRLab

Most of the naked-eye star sightings came from Europe and the United States, said Christopher Kyba, one of the authors of the study, but there was also good participation in Uruguay, South Africa and Japan.

“The global trend in skyglow that we measure probably reflects the trend in countries with the fastest increases in economic development, because the rate of change in light emissions is highest there,” the researchers said.

The study coincided with the replacement of many outdoor lights with light-emitting diodes (LEDs), but the researchers said the impact on skyglow from the switch to LEDs is unclear.

“Some researchers have predicted that it will be beneficial; others, that it could be harmful due to spectral changes or rebound effect, in which the high luminous efficiency of the LEDs is the result of installing more lights or brighter lights or longer operating hours,” they said.

According to the study, the share of the global LED market for new general lighting grew from less than one percent in 2011 to 47 percent in 2019.

“The visibility of stars is rapidly deteriorating, despite (or perhaps because of) the introduction of LEDs in outdoor lighting applications,” the researchers said.

“Current lighting policies are not preventing increases in skyglow, at least on continental and global scales.”

‘Fighting the cosmos’

Kyba, a physicist at the German Research Center for Geosciences, told AFP that while the team was able to assess the erosion of star visibility due to the sky, little research has been done on its ecological impact.

“There is a lot of research on the light shining directly on animals and plants,” he said. “But it is very difficult to do experiments on the influence of the sky.

“You’re not going to do something like just turn off New York and see what happens in the East River.”

Science aside, light pollution has changed the character of the night sky.

“For all of human history, when people went out at night, they were sort of against the cosmos, at least on clear nights with no moon,” Kyba said.

“You walk outside and the stars are there, the Milky Way is there. It’s there and it’s shining down on you,” he said.

“And now that’s like a really unusual experience,” he said. “It certainly makes a difference to us as people who don’t have this experience which used to be a very universal experience.”

The Globe at Night campaign is hosting an interactive data map at and is looking for volunteers to collect more observations in 2023.

More information:
Citizen scientist Christopher CM Kyba reports rapid global declines in star visibility from 2011 to 2022, Science (2023). DOI: 10.1126/science.abq7781.

Fabio Falchi et al, Light pollution is skyrocketing, Science (2023). DOI: 10.1126/science.adf4952 ,

More information on “Globe at Night” can be found here.

© 2023 AFP

Quote: Star visibility eroding rapidly as night sky brightens: study (2023, January 22) retrieved January 22, 2023 from -rapidly-night.html

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