Light pollution is erasing stars from the night sky at breakneck pace. It's only going to get worse.

Light pollution is worsening globally, virtually erasing stars from the night sky.
Where18 years ago, one would see 250 stars adorning the night sky, there are only 100 to be seen today. (Image credit: NOIRLab/NSF/AURA, P. Marenfeld)

Light pollution is brightening up the night sky so fast that stars are virtually disappearing in front of sky-watchers' eyes, a new study has revealed. 

Where 18 years ago, a star gazer would see on average 250 specks of light illuminating the darkness overhead. Today, only 100 would be visible, according to the study that relied on information from thousands of citizen scientists all over the world. 

The reason behind this unprecedented star loss is the increase in light pollution, the effect of artificial urban lightning that, according to the study, leads to an average 9.6% global annual rise in the brightness of the sky. This pace of sky-brightening is quite a bit faster than satellite measurements have indicated previously, the study's authors said in a statement (opens in new tab)

The sky is brightening up at a different rate in different parts of the world. In Europe, the pace appears slightly slower at 6.5% per year, whereas in North America the night glow of the sky increases by 10.4% every year, the study found.

Related: Challenge for astronomy: Megaconstellations becoming the new light pollution

"The rate at which stars are becoming invisible to people in urban environments is dramatic," Christopher Kyba, of the GFZ German Research Centre for Geosciences and lead author of the study, said in the statement. 

The study was conducted by researchers from the GFZ German Research Center for Geosciences, the Ruhr-Universität Bochum and the US National Science Foundation’s NOIRLab. The analysis, dubbed the "Globe at Night" Citizen Science Project, included 50,000 naked eye night sky observations made by volunteers between 2011 and 2022 . 

The lack of darkness at night is concerning for far more people than just professional astronomers and astronomy enthusiasts. According to Constance Walker, co-author of the study and head of the Globe at Night project of NSF's NOIRLab, the unceasing exposure to light affects all humans as well as animals living in affected regions. 

"Skyglow affects both diurnal [active during the day] and nocturnal animals and also destroys an important part of our cultural heritage," Walker said in the statement. 

The nighttime glow of the sky has not previously been measured globally, the researchers said, but estimates exist based on satellite measurements. Those measurements, however, have previously indicated that the increase in light pollution has plateaued and is even mildly decreasing in the most affected areas in Europe and North America. The new findings show that these earlier estimates were likely wrong. 

"Satellites are most sensitive to light that is directed upwards towards the sky. But it is horizontally emitted light that accounts for most of the skyglow," Kyba said. "So, if advertisements and facade lighting become more frequent, bigger or brighter, they could have a big impact on skyglow without making much of a difference on satellite imagery."

On top of that, satellite sensors are less sensitive to LED lighting that has become more common in recent years, which glows in hues of blue, compared to the orange-glowing sodium vapor lamps that were dominant in the past. 

"Our eyes are more sensitive to blue light at night, and blue light is more likely to be scattered in the atmosphere, so it contributes more to skyglow," Kyba said. "But the only satellites that can image the whole Earth at night are not sensitive in the wavelength range of blue light."

The researchers noted that one shortcoming of the study is that it didn't have enough data from the developing world where changes may be happening at an even faster rate. 

The study (opens in new tab) was published on Thursday (Jan. 19) in the journal Science.

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Tereza Pultarova
Senior Writer

Tereza is a London-based science and technology journalist, aspiring fiction writer and amateur gymnast. Originally from Prague, the Czech Republic, she spent the first seven years of her career working as a reporter, script-writer and presenter for various TV programmes of the Czech Public Service Television. She later took a career break to pursue further education and added a Master's in Science from the International Space University, France, to her Bachelor's in Journalism and Master's in Cultural Anthropology from Prague's Charles University. She worked as a reporter at the Engineering and Technology magazine, freelanced for a range of publications including Live Science, Space.com, Professional Engineering, Via Satellite and Space News and served as a maternity cover science editor at the European Space Agency.

  • FredJ1056
    I agree. Here in Michigan alone, the sky is getting so bright due to all the LED lighting that is excessive in many areas. Buildings with all the unshielded wall packs and property lights that are aimed at an angle that distract and nearly blind motorists and anyone who happens to look in the general direction. Residential lighting is becoming more of a problem too, with many of the lights without motion sensors to regulate them.
    What our state really needs sadly, is some good legislation that puts limits on how many fixtures are in a given area , types of installations, wattage of lighting, and encourages motion activation technology, to help curb this ever growing problem. 🙁
    Reply
  • Echoii
    I think we need laws on lighting, there are houses near my house that have spotlights in the driveway pointing up to light up their cars at night, WHY??!? No one wants to look at your BMW in the middle of the night!

    Pointless
    Reply
  • Classical Motion
    I had to put up an outside motion light/camera. Someone was siphoning my gasoline.
    Reply
  • Pogo
    The motion sensor is the ticket. The light going on is what alerts you, and the bad guys usually go away if it suddenly goes on.
    My neighbor has a very bright light pointing sideways across his driveway and my yard. But, he just ain’t watching the yard at 3 a.m. And half the light is wasted to my night sky. I’m lucky to see much more than the moon, Venus and Jupiter.
    Reply
  • Classical Motion
    I quit looking at the nite sky. I move here in 2001. And every DAMN time I want to look at an event..........cloud cover. It's unreal. A curse. So I wait and check things out on the net.
    Reply
  • Pogo
    @Classical Motion: you in Seattle or UK? That sounds like their standard climate situation.
    Reply
  • Classical Motion
    Roanoke, Va. And the light pollution is terrible here also. Look at the space night time view. We are a huge light emitter. One has to drive several miles and find a shadow, in order to see the nite sky.

    We do have a dark spot just north of us. You can see it on the space view. It's for the Green Bank Observatory. RF transmission is restricted in that zone. Some might want to try some of the dark spots on the image for their skyward observations.
    Reply
  • Pogo
    Eastern PA, north of Philadelphia. I can even see the sky glow from NYC. I watch the flight patterns for JFK, LaGuardia, and Newark.
    Reply