Stars disappearing from human sight at ‘astonishing rate’, say scientists

Stars in the night sky are disappearing from human sight at an “astonishing rate” due to rapidly growing light pollution, scientists have warned.

Astronomers believe an increase in the use of light-emitting diode (LED) bulbs – which are more energy efficient compared to traditional lights – may be contributing to the trend.

They said artificial lighting, also called skyglow, had increased the overall sky brightness at a rate of 9.6% per year – with stars disappearing from human sight more rapidly than indicated by satellite measurements.

Dr Christopher Kyba, a researcher at the German Research Centre for Geosciences, said: “At this rate of change, a child born in a location where 250 stars were visible, would be able to see only about 100 by the time they turned 18.”

The researchers said that on a clear dark night, the human eye should be able to see several thousand stars.

But they added that growing light pollution meant that around 30% of people around the globe were unable to get a nightly view of their home galaxy – the Milky Way.

For the study, Dr Kyba and his team of researchers analysed more than 50,000 observations made by citizen scientists as part of the Globe at Night project run by the US National Science Foundation’s NOIRLab.

They looked at observations submitted between 2011 and 2022, focusing on data from Europe and North America.

Their findings showed an increase in sky brightness at a rate of 9.6% per year in the last 12 years – much greater than the roughly 2% per year increase calculated using satellite data, which the team described as “astonishing”.

According to the researchers, this was because existing satellites were not well suited to measuring skyglow as it appeared to humans – particularly LEDs.

Dr Kyba said: “This shows that existing satellites aren’t sufficient to study how Earth’s night is changing.”

He added: “Since human eyes are more sensitive to these shorter wavelengths at night-time, LED lights have a strong effect on our perception of sky brightness.

“This could be one of the reasons behind the discrepancy between satellite measurements and the sky conditions reported by Globe at Night participants.”

The researchers said light pollution had many detrimental effects on human health and wildlife, as it disrupted the transition from sunlight to starlight that biological systems have evolved to depend on.

Connie Walker, an astronomer at the National Radio Astronomy Observatory in the US, said: “The increase in skyglow over the past decade underscores the importance of redoubling our efforts and developing new strategies to protect dark skies.”

The findings are published in the journal Science Advances.