Starlink is the name of a satellite network developed by the private spaceflight company SpaceX to provide low-cost internet to remote locations. SpaceX eventually hopes to have as many as 42,000 satellites in this so-called megaconstellation.
The size and scale of the project flusters astronomers, who fear that the bright, orbiting objects will interfere with observations of the universe, as well as spaceflight safety experts who now see Starlink as the number one source of collision hazard in Earth's orbit. In addition to that, some scientists worry that the amount of metal that will be burning up in Earth's atmosphere as old satellites are deorbited, could trigger unpredictable changes to the planet's climate.
Starlink:The initial plan
SpaceX's satellite internet proposal was announced in January 2015. Though it wasn't given a name at the time, CEO Elon Musk said that the company had filed documents with international regulators to place about 4,000 satellites in low Earth orbit.
"We're really talking about something which is, in the long term, like rebuilding the internet in space," Musk said during a speech in Seattle when revealing the project. (Musk also owns electric car company Tesla, but Tesla does not produce satellites.)
Musk's initial estimate of the number of satellites soon grew, as he hoped to capture a part of the estimated $1 trillion worldwide internet connectivity market to help achieve his Mars colonization vision. The U.S. Federal Communications Commission (FCC) has granted SpaceX permission to fly 12,000 Starlink satellites, and the company has filed paperwork with an international regulator to loft up to 30,000 additional spacecraft.
To put that into perspective, as of Jan.5 2022, 12,480 satellites have been launched in all of history with only 4,900 still active, according to the European Space Agency.
SpaceX launched its first two Starlink test craft, named TinTinA and TinTinB, in February 2018. The mission went smoothly. Based on initial data, the company asked regulators for its fleet to be allowed to operate at lower altitudes than originally planned, and the FCC agreed.
The first 60 Starlink satellites launched on May 23, 2019, aboard a SpaceX Falcon 9 rocket. The satellites successfully reached their operational altitude of 340 miles (550 kilometers) — low enough to get pulled down to Earth by atmospheric drag in a few years so that they don't become space junk once they die.
How Starlink satellites work
The current version of each Starlink satellite weighs 573 lbs. (260 kilograms) and is, according to Sky & Telescope magazine, roughly the size of a table.
Rather than sending internet signals through electric cables, which must be physically laid down to reach far-flung places, satellite internet works by beaming information through the vacuum of space, where it travels 47% faster than in fiber-optic cable, Business Insider reported.
Current satellite internet works using large spacecraft that orbit 22,236 miles (35,786 km) above a particular spot on Earth. But at that distance, there are generally significant time delays in sending and receiving data. By being closer to our planet and networking together, Starlink’s satellites are meant to carry large amounts of information rapidly to any point on Earth, even over the oceans and in extremely hard-to-reach places where fiber-optic cables would be expensive to lay down.
Musk has said that the Starlink network would be able to provide "minor" internet coverage after 400 spacecraft were up and running, and "moderate" coverage after about 800 satellites became operational.
As of early January 2022, SpaceX had launched more than 1,900 Starlink satellites overall. The constellation is now providing broadband service in select areas around the world, as part of a beta-test program with download speeds of between 100 Mb/s and 200 Mb/s and latency as low as 20 milliseconds, according to a Starlink guide.
Users on the ground access the broadband signals using a kit sold by SpaceX. The kit contains a small satellite dish with mounting tripod, a wifi router, cables and a power supply, according to the company's website.
Starlink versus astronomy
Within days of the first 60-satellite Starlink launch, skywatchers spotted a linear pearl string of lights as the spacecraft whizzed overhead in the early morning. Web-based guides showed others how to track down the spectacular display.
"This was quite an amazing sight, and I was shouting 'Owowowow!' when the bright 'train' of objects entered into view," Netherlands-based satellite tracker Marco Langbroek told Space.com in 2019 via email. "They were brighter than I had anticipated."
That brightness was a surprise to almost everyone, including both SpaceX and the astronomical community. Researchers began to panic and shared photos of satellite streaks in their data, such as this one from the Lowell Observatory in Arizona.
They expressed particular concerns about future images from highly sensitive telescopes such as the Vera Rubin Observatory (formerly known as the Large Synoptic Survey Telescope), which will study the entire universe in exquisite detail and is expected to come online in 2022. Radio astronomers are also planning for interference from Starlink's radio-based antennas.
The International Astronomical Union (IAU) expressed concerns in a statement released in June 2019. "Satellite constellations can pose a significant or debilitating threat to important existing and future astronomical infrastructures, and we urge their designers and deployers as well as policy-makers to work with the astronomical community in a concerted effort to analyze and understand the impact of satellite constellations," the statement said.
In April 2021, Thomas Schildknecht, the deputy director of the Astronomical Institute of the University of Bern, who represents Switzerland in the IAU, said at the European Space Agency's space debris conference that the union was calling on the United Nations to protect pristine night sky as cultural heritage against the uncontrolled expansion of megaconstellations.
In a report released in October 2022, the American Astronomical Society (ASS) likened the impact of megaconstellations on astronomy to light pollution. The report said the sky may may brighten by a factor of two to three due to diffuse reflection of sunlight off the spacecraft.
Starlink as a major source of orbital collision risk
SpaceX received more backlash in September 2019, when the European Space Agency (ESA) announced that it had directed its Aeolus satellite to undertake evasive maneuvers and avoid crashing into "Starlink 44," one of the first 60 satellites in the megaconstellation. The agency took action after learning from the U.S. military that the probability of a collision was 1 in 1,000 — 10 times higher than ESA's threshold for conducting a collision-avoidance maneuver.
In August 2021, Hugh Lewis, the head of the Astronautics Research Group at the University of Southampton, U.K. and Europe's leading space debris expert, told Space.com that Starlink satellites represent the single main sources of collision risk in low Earth orbit.
According to computer models, at that time, Starlink satellites were involved every week in about 1,600 encounters between two spacecraft closer than 0.6 miles (1 kilometer). That's about 50% of all such incidents. This number rises with every new batch of satellites launched into space. By the time Starlink deploys all 12,000 satellites of its first-generation constellation it could reach 90%, Lewis said.
Lewis also expressed concerns that Starlink's operator SpaceX, a newcomer into the satellite business, is now the single most dominant player in the field whose decisions can affect safety of all operations in low Earth orbit.
Starlink's effects on the atmosphere
SpaceX plans to refresh the Starlink megaconstellation every five years with newer technology. At the end of their service, the old satellites will be steered into Earth's atmosphere where they will burn up. That is certainly commendable when it comes to space debris prevention, however, there is another problem.
The vast amount of satellites that will be burning in the otherwise pristine upper layers of the atmosphere could actually alter the atmospheric chemistry and have unforeseen consequences for life on the planet.
In a paper published in May 2021 in the journal Scientific Reports, Canadian researcher Aaron Boley said the aluminum the satellites are made of will produce aluminum oxide, also known as alumina, during burn-up. He warned that alumina is known to cause ozone depletion and could also alter the atmosphere's ability to reflect heat.
"Alumina reflects light at certain wavelengths and if you dump enough alumina into the atmosphere, you are going to create scattering and eventually change the albedo of the planet," Boley told Space.com.
That could lead to an out-of-control geoengineering experiment, a change in the Earth's climate balance. The effects of such alternations are currently unknown.
Karen Rosenlof, an atmospheric chemistry expert at the National Oceanic and Atmospheric Administration (NOAA), told Space.com she too was concerned about the effects of the particles from the burning satellites in the atmosphere. Rosenlof actually has expertise in modelling the effects of geoengineering interventions.
David Fahey, the Director of NOAA's Chemical Sciences Laboratory, and Martin Ross, a physics and meteorology scientist at the Aerospace Corporation, both told Space.com that more research is urgently needed to understand the effects of burning increasing amounts of satellites in the atmosphere.
The problem, the scientists said, is that in those high layers of the atmosphere, the particles are likely going to stay forever.
Boley said that while the amount of satellites burning in the atmosphere will be considerably smaller than the amount of meteorites, the chemical composition of the artificial objects is different, thus the presence of the products of their burning is something scientists know nothing about.
"We have 54 tonnes (60 tons) of meteoroid material coming in every day," Boley said. "With the first generation of Starlink, we can expect about 2 tonnes (2.2 tons) of dead satellites reentering Earth's atmosphere daily. But meteoroids are mostly rock, which is made of oxygen, magnesium and silicon. These satellites are mostly aluminum, which the meteoroids contain only in a very small amount, about 1%."
As the accumulation of those particles would increase over time, so would the intensity of the effects. It thus cannot be ruled out that over decades the pollution from burning megaconstellation satellites could lead to changes on a scale akin to what we are currently experiencing with fossil-fuel-induced climate change.
"Humans are exceptionally good at underestimating our ability to change the environment," said Boley. "There is this perception that there is no way that we can dump enough plastic into the ocean to make a difference. There is no way we can dump enough carbon into the atmosphere to make a difference. But here we are. We have a plastic pollution problem with the ocean, we have climate change ongoing as a result of our actions and our changing of the composition of the atmosphere and we are poised to make the same type of mistake by our use of space."
Starlink did not respond to Space.com requests for comment.
What SpaceX plans to do
SpaceX has stated that it will work with organizations and space agencies to mitigate the impacts of its megaconstellation. And the company has tried to assuage astronomers' concerns over Starlink's effect on the night sky.
"SpaceX is absolutely committed to finding a way forward so our Starlink project doesn't impede the value of the research you all are undertaking," Patricia Cooper, SpaceX's vice president of satellite government affairs, told astronomers at a January 2020 meeting of the American Astronomical Society in Honolulu, Nature reported.
SpaceX has taken action to this effect. For example, recently launched Starlink satellites sport visors designed to prevent sunlight from glinting too brightly off their most reflective parts.
But the huge numbers of satellites in megaconstellations from SpaceX and other private space companies, such as OneWeb, suggest that light-pollution and other issues may continue, and advocates have called for greater regulations from government agencies.
"Here is a gift for the leaders of the world, a task more non-partisan than any other which has come before: protect our skies," stargazer Arwen Rimmer wrote in The Space Review, a weekly online publication devoted to essays and commentary about space, in early 2020.
- Watch this video describing the Starlink satellite project, from SpaceX.
- Read how astrophysicist Ethan Siegel thinks SpaceX can fix the damage Starlink satellites are causing to astronomy, published in Forbes.
- Follow the #starlink hashtag on Twitter to catch the latest news and opinions about Starlink.
NOIRLab, Report of the SATCON2 Workshop: Executive Summary, July 16, 2021 https://noirlab.edu/public/media/archives/techdocs/pdf/techdoc031.pdf
Boley, A., Byers, M. Satellite mega-constellations create risks in Low Earth Orbit, the atmosphere and on Earth, Scientific Reports, 20 May, 2021 https://www.nature.com/articles/s41598-021-89909-7
McDowell, J. The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink Constellation, The Astrophysical Journal Letters, April 6 2020 https://iopscience.iop.org/article/10.3847/2041-8213/ab8016/meta
Massey R. et al. The challenge of satellite megaconstellations, Nature Astronomy, 6 November, 2020
This article was updated on January 6, 2022 by Space.com senior writer Tereza Pultarova.