GoKawiilPress Release
"Beyond the limit": one million satellites and mirrors in space pose grave threat to the night sky
A new European Southern Observatory (ESO) study has found that current proposals to launch over 1.7 million satellites into orbit, including extremely bright ones, would have “devastating consequences for astronomy.” According to the study, no more than 100 000 faint satellites, below naked eye visibility, should orbit Earth, to safeguard our ability to observe the night sky with modern telescopes. The study is the first to compute the extent to which large and bright satellite constellations — which have also raised concerns about their impacts on health and the environment — would affect astronomical observations by making the night sky brighter.
Since 2019, the number of satellites orbiting Earth has increased rapidly, to over 14 000 today [1] — dominated by SpaceX's Starlink telecommunications satellites. Satellite proposals have also escalated, both in number and in potential impact. "Until now we have managed, but it's getting worse," stresses Olivier Hainaut, who has been involved in developing recommendations to mitigate the impact of satellite constellations on astronomy. While companies like SpaceX have taken measures to make their satellites less bright, current satellite proposals are going “beyond the limit” of what astronomy can withstand, he says. Hainaut, an astronomer at ESO for over 30 years, is the author of the peer-reviewed study on the impacts of satellite constellations accepted for publication in Astronomy & Astrophysics.
SpaceX plans to send one million more satellites into orbit, for space-based data centres, which would significantly alter the appearance of the sky. The new study shows that, for a large fraction of each night, hundreds of satellites would be visible and, at certain times, up to several thousand, similar to the number of stars seen with the naked eye in good conditions. Other planned satellite constellations such as E-Space's Cinnamon and China’s CTC-1 and 2 would add hundreds of thousands more satellites into orbit, compounding the problem.
Reflect Orbital, a US start-up, aims to launch a constellation of very large mirror-like satellites to provide sunlight at night, with reflected beams that span at least five kilometres on Earth's surface. They intend to start with a prototype satellite in orbit this year and plan to increase their satellite population to 50 000 by 2035. These satellites would be the brightest ever in orbit, with damaging consequences for dark skies on Earth. Hainaut's calculations show that the full constellation would fill the night sky with hundreds of very brightly visible satellites. Seen from within a reflected beam, the satellite delivering sunlight would appear four times brighter than the full Moon. Even if no satellite points its beam directly at an observer, each would be as bright as the planet Venus, the ‘morning star’. From a light-polluted city, like Munich, Germany, these hundreds of satellites would be the only ‘stars’ visible in the night sky.
These proposals, combined with others considered in the study, would dramatically brighten the night sky, hindering humankind’s ability to observe faint cosmic targets, including far-away galaxies, some Earth-like planets around other stars, and even asteroids potentially dangerous to Earth.
Bright trails and brighter skies
Hainaut explains that "satellites, illuminated by the Sun, are much brighter than distant galaxies. When a satellite crosses what we observe, it makes a bright streak on our image, zapping whatever is behind it."
To compute the impact of this and other effects of satellite constellations on astronomical observations, Hainaut simulated the positions, motion and brightness of all present and planned satellite constellations.
... continue reading