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Satellites, space debris may have already brightened night skies 10% globally – and it's going to get worse

Goodbye darkness, my old friend

Constellations of satellites and chunks of space debris orbiting Earth and reflecting sunlight may have lightened our night skies by more than 10 per cent, scientists say. We're also told the light pollution is increasing.

“We expected the sky brightness increase would be marginal, if any, but our first theoretical estimates have proved extremely surprising and thus encouraged us to report our results promptly," said Miroslav Kocifaj, a senior researcher at the Slovak Academy of Sciences and lead author of a study into the light pollution, published today in the Monthly Notices of the Royal Astronomical Society.

Astronomers have previously complained that SpaceX’s Starlink sats flitting across the sky get in the way of astronomical observations. Gleaming from the Sun's brilliance, they can appear as a moving string of lights. Although concerns have been raised about the increased brightness from stuff in orbit, the International Astronomical Union initially said it did not yet have a good grasp on their wider impact.

Now, a team of researchers have calculated that the overall brightness of Earth's night sky may have been raised by more than 10 percent above natural light levels by humankind's space-faring activities. Thus, truly dark nights – wherever you are, even away from cities and towns – could be increasingly hard to find.


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“Unlike ground-based light pollution, this kind of artificial light in the night sky can be seen across a large part of the Earth’s surface,” said John Barentine, co-author of the paper and director of public policy for the International Dark-Sky Association, a non-profit org led by astronomers. The expansive glow means that even the darkest parts with little light pollution will still be affected.

“Astronomers build observatories far from city lights to seek dark skies, but this form of light pollution has a much larger geographical reach,” he added.

The problem will only get worse as more satellites are flung into the sky. Other culprits also include spent rocket components and other bits of debris that reflect and scatter light from the Sun.

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Here’s an extreme example of just how bright these objects can be. Last week, it appears one of SpaceX’s Falcon 9 rockets, which was launched on March 4 to put a bunch of Starlink birds into orbit, reentered our atmosphere over the west of the United States. Whatever it was – likely the rocket's second stage – it put on an unexpected light show for Americans. No debris was reported making it to ground level. Below is a video capturing the moment:

SpaceX is attempting to fix the glaring brightness of its satellites. Last year, it launched one that sported a visor to deflect sunlight.

“Our results imply that many more people than just astronomers stand to lose access to pristine night skies,” Barentine said. “This paper may really change the nature of that conversation.” ®

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