Last week SpaceX launched the first 60 satellites in its Starlink Internet transmission network. Although people are currently excited at spotting the satellite train, astronomers – both amateur and professional – are worried about what they will do to the night sky in future, and they're not finding Elon Musk's response satisfying.
In places where Internet cables are lacking, Starlink's promise of ultrafast Internet access could prove very attractive, but the price could be losing something humans have always cherished – the beauty of the night sky.
When Starlink was proposed astronomers anticipated the satellites would be faint enough to limit the problem. With the first deployment proving brighter than expected, fears are escalating, although it is hoped they will dim significantly once the solar panels are properly orientated.
These days anyone spending time staring at the night sky away from city lights will see satellites. They've allowed astonishing improvements in global communication and saved millions of lives through the improvements they've offered in weather predictions. Poets might mourn confusing them with “shooting stars”, but astronomers have learned to live with the lines they produce across space photographs.
At the moment, the Starlink satellites are different only in that they form a train following each other. Indeed, as a novelty, they've attracted more people to look at the sky to seek the line of moving dots, like an unseasonal Santa's sleigh whizzing across the sky.
What has a lot of people worried, however, is that SpaceX has sought approval to deploy 12,000 of them, compared to 5,000 satellites currently in orbit. This could make for a night sky in which artificial glints are the norm, and stars the exception.
Satellites don't produce their own light, so they can't be seen when they are in Earth's shadow. According to Musk, and some who agree with him, that will be most of the time.
However, astronomers have pointed out that satellites in these orbits stay visible for longer at higher latitudes. In summer, when looking at the sky is most popular, much of Starlink's fleet could be visible from Europe and northern North America through the entire night.
There are other concerns as well. Starlink satellites will be placed in low-Earth orbit. This is cheaper than going higher up, but that area of space is getting crowded. Any object struck by a piece of spacejunk could break up into dozens of pieces, each of which will be a menace to every other satellite at similar heights. For decades space scientists have feared what they call the Kessler Syndrome, the avalanche that could be produced in such a scenario. The more objects we put there, the greater the danger becomes.
To avoid this, Starlink satellites will be on the lookout for threats, and have the capacity to move to adjust their orbits. However, Dr Alice Gorman of Flinders University fears this capacity may not be enough.
Two-thirds of Starlink's proposed satellites will be in low enough orbits that drag from the outer atmosphere will cause them to spiral in, and eventually burn up, soon after their mission ends. Unfortunately, the other third are much higher, and will last for thousands of years unless we find some way to dispose of them.