There are over 40,000 pieces of tracked space debris, and while many occupy low-Earth orbit, there are a large number of objects whose orbits extend many thousands of miles/kilometers away from the Earth. With enough objects in low-Earth orbit, a solar flare will potentially disable them, leading to not only a collision, but a chain reaction of collisions. In the worst-case scenario, Kessler syndrome becomes a real risk. (Credit: NOIRLab/NSF/AURA/P. Marenfeld)

Will Musk’s Starlink satellites lead to Kessler syndrome?

Space weather poses a tremendous threat to all satellites, knocking all computer systems offline. Is that a recipe for Kessler syndrome?

Ethan Siegel

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Starts With A Bang!

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10 min read

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5 days ago

Over the course of the 2020s and 2030s, the night sky and the volume of space that surrounds the Earth are both poised to become very different than they’ve been for all of human history. As of 2019, all of humanity had launched an estimated total of between 8,000 and 9,000 satellites, where approximately 2,000 of them were still active back then, mostly in low-Earth orbit. As many companies now scramble to provide worldwide 5G coverage from space — led most prominently by Elon Musk’s and SpaceX’s Starlink, which has by far the most satellites — humanity is now beginning to enter the era of satellite mega-constellations.

As of today in 2023, however, there are nearly 9000 active satellites, with active Starlinks making up the overwhelming majority of them: 4755 out of the 8647 active satellites, or 55% of them. While media coverage has largely focused on only one detrimental effect so far — the damage that these satellites have already caused and are still causing to astronomy — there’s a second consequence that could be even more disastrous over the long-term: Kessler syndrome. With tens or even hundreds of thousands of satellites in orbit, a single collision could trigger a chain reaction. With the realities of solar flares, coronal mass ejections, and other forms of space weather, the era of mega-constellations may usher in a new type of natural disaster, making Earth’s orbit impassable to all future space-based missions.

Over a hundred thousand human-made objects — 95% of them “space junk” — occupy low and medium Earth orbit. Each black dot in this image shows either a functioning satellite, an inactive satellite, or a large-enough piece of debris. The current and planned 5G satellites will vastly increase both the number and the impact that satellites have, and raise the potential for Kessler syndrome.

The idea of Kessler syndrome is a simple one: if there are too many satellites around Earth, an unfortunate collision between any two of them could create enough debris that another collision becomes inevitable. Although there is not widespread agreement on when that point will be reached, it’s widely recognized that greater numbers of larger satellites greatly increases this risk. With Starlink alone proposing a total of 42,000 satellites in three different orbital…