#Jessica Heim
Since time immemorial, humans around the world have gazed up in wonder at the night sky. The starry night sky has not only inspired countless works of music, art and poetry, but has also played an important role in timekeeping, navigation and agricultural practices in many traditions.
For many cultures, the night sky, with its stars, planets and the Milky Way, is considered just as important a part of the natural environment.
However, the night sky is changing. Not only is ground-based light pollution increasing rapidly, but growing numbers of satellites and space debris in orbit around Earth are also impacting the night sky.
Earlier research showed that satellites and space debris may increase the overall brightness of the night sky.
A brighter sky
Since 2019, the number of functional satellites in orbit has more than doubled to around 7,600. The increase is mostly due to SpaceX and other companies launching large groups of satellites to provide high-speed internet communications around the world.
By the end of this decade, we estimate, there may be 100,000 satellites in orbit around the Earth. Collisions that generate space debris are more likely as space fills with new satellites. Other sources of debris include the intentional destruction of satellites in space warfare tests.
Increasing numbers of satellites and space debris reflect ever more sunlight towards the night side of Earth. This will almost certainly change the appearance of the night sky and make it harder for astronomers to do research.
One way satellites impact astronomy is by appearing as moving points of light, which show up as streaks across astronomers' images. Another is by increasing diffuse night sky brightness. This means all the satellites that are too dim or small to be seen individually, as well as all the small bits of space debris, still reflect sunlight, and their collective effect is to make the night sky appear less dark.
Brighter night skies mean longer exposures through telescopes are needed to see distant objects in the cosmos. This will mean that for projects with a fixed amount of observing time, less science will be accomplished, and there will be increased competition for telescope access.
In addition, brighter night skies will also reduce the detection limits of sky surveys, and dimmer objects may not be detected, resulting in missed research opportunities.
