SpaceX; Kevork Djansezian/Getty; Business Insider
The company's planned network could eventually include up to 42,000 satellites.
Too many bright satellites could make astronomy "impossible," one scientist told the New York Times.
Sending many satellites into orbit also increases the risk of collisions. In the worst case scenario, crashes could spiral into a catastrophe that cuts off our access to space.
SpaceX launched 60 internet satellites into space on Monday.
The recent batch — the second such group Elon Musk's rocket company has sent into orbit — is part of SpaceX's plan to blanket Earth in high-speed satellite internet. The company launched its first batch of 60 satellites in May and hopes to finish the project, called Starlink, in 2027. By then, the network could include up to 42,000 satellites.
But that plan has many scientists worried about the future of astronomy.
They fear that the SpaceX satellites are too bright and could form a "megaconstellation" that blots out the stars. If that happens, astronomers wouldn't be able to observe the universe from Earth.
"If there are lots and lots of bright moving objects in the sky, it tremendously complicates our job," astronomer James Lowenthal told the New York Times. "It potentially threatens the science of astronomy itself."
What's more, 42,000 satellites would be more than eight times the total number of satellites in orbit today, according to estimates by the European Space Agency. Adding that much more material to Earth's orbit would increase the risk that a catastrophic series of collisions could turn the region into a minefield of debris.
In the worst-case scenario, a spiraling space-junk disaster could cut off our ability to leave Earth.
'It will look as if the whole sky is crawling with stars'
Mark Handley/University College London
When SpaceX launched its first set of Starlink satellites, many astronomers were alarmed by how bright the new objects were. In the days following the launch, people across the world spotted the train of satellites, as bright as stars.
"I felt as if life as an astronomer and a lover of the night sky would never be the same," Lowenthal said.
SpaceX did not respond to Business Insider's request for comment about this or other points in this story in time for publication.
Most of the company's Starlink satellites have since moved into higher ranges of orbit, but some are still visible in rural areas with dark night skies, according to the Times.
If SpaceX launches thousands more satellites, "it will look as if the whole sky is crawling with stars," Lowenthal said.
A telescope on Earth that's designed to look for distant, dim objects would easily pick up these false stars.
The upcoming Large Synoptic Survey Telescope (LSST) in Chile is one such telescope. Scheduled for completion in 2022, it will study the mysterious forces of dark matter and dark energy. The LSST will also chart objects that change or move across the sky, including potentially hazardous asteroids flying dangerously close to Earth.
Researchers worry that Starlink satellites could mess with that data. A single satellite could create a long streak of light across the telescope's long-exposure images of the sky, creating false signals and blocking astronomers' view of the objects they want to study.
These streaks would be even worse in summer, according to an editorial in the journal Nature, because satellites would be visible for longer periods of time. That seasonal imbalance would skew LSST data in long-term studies.
Researchers are exploring their ability to maneuver the LSST around the new satellites. But simulations based on earlier SpaceX plans to launch 12,000 satellites (30,000 less than the current plan calls for) suggested the satellites would be unavoidable 20% of the time, the Times reported.
The satellites would be most visible around dusk and dawn — when telescopes are best able to track asteroids flying too close to Earth.
"We're redoing the models now just to see what's visible at any one time — and it's really quite frightening," Patrick Seitzer, an astronomer who has been running such simulations, told the Times.
SpaceX's plan could make astronomy 'impossible'
SpaceX via Twitter
SpaceX has said it plans to paint its satellites black on the sides that face Earth, making them less reflective. (It did not appear to have done so for the recently launched batch, however.) But even if it did paint them, telescopes like LSST would still be able to detect the satellites' light, Tyson said.
What's more, the black paint would do nothing to cover radio waves.
Satellite communications use wavelengths similar to the ones radio telescopes on the ground use to study objects in space. For now, the radio interference from satellites is manageable for most telescopes. But that would likely change if the number of satellites in orbit grows from the current total of 2,000 to something closer to 50,000.
The National Radio Astronomy Observatory has been talking with SpaceX about switching satellite communications to different radio frequencies, Nature reported.
The American Astronomical Society (AAS) has also been meeting with SpaceX to discuss the impact of its satellites, according to the Times. Lowenthal is one of the experts on that committee.
"So far, they've been quite open and generous with their data," he said. "But they have not made any promises."
Other companies, including Amazon, Telesat, and OneWeb, are also working on plans to launch their own satellite constellations, though none are as expansive as SpaceX's.
"There is a point at which it makes ground-based astronomy impossible to do," astronomer Jonathan McDowell told the Times. "I'm not saying Starlink is that point. But if you just don't worry about it and go another 10 years with more and more mega-constellations, eventually you are going to come to a point where you can't do astronomy anymore."
Too many satellites could lead to a space-junk catastrophe
Over 100 million bits of junk surround Earth, from abandoned satellites, spacecraft that broke apart, and other space missions. Each piece of debris, no matter how small, travels at speeds high enough to inflict catastrophic damage to vital equipment. A single hit could be deadly to astronauts on a spacecraft.
The more stuff we put into orbit, the higher the risk of collisions becomes.
Any potential collision would fragment satellites or other orbiting objects into smaller pieces, making additional collisions more likely. If such a situation were to spiral out of control, that could spur a catastrophic chain of crashes known as a Kessler event.
Theoretically, one collision could create and spread bits of junk that then cause another collision, which in turn begets more debris and leads to a chain of crashes. Eventually, Earth would wind up surrounded by a field of debris so impassible that any spacecraft passing through would be unable to avoid catastrophic collisions.
Donald J. Kessler, who used to work at NASA's Johnson Space Center, first put forward this worst-case scenario in a 1978 study. In it, he calculated that it could take hundreds of years for such debris to clear up enough to make spaceflight safe again.
Most astronomers agree that a Kessler event is unlikely today, however.
Starlink satellites have already raised concerns about collisions
When launching its first batch of Starlink satellites, SpaceX said it planned to "deorbit" two satellites by using ion engines to move them into Earth's atmosphere, where they would burn up. This would demonstrate how the company could remove old or broken satellites from orbit, thereby lowering the risk of collisions.
Those satellites had not yet deorbited as of October 27, according to observations by McDowell.
SpaceX and Amazon are also both designing their satellites to be able to avoid collisions through automatic or operator-directed maneuvers. But even so, a recent Amazon filing to the FCC suggested that if 5% of its satellites fail (or their avoidance systems do), the risk of a collision in a large constellation would be around 6%.
Such a rate is "well beyond what Amazon would view as expected or acceptable," the company wrote in a letter to the FCC.
For its part, SpaceX has seen a 5% failure rate with its first batch of 60 Starlink satellites: Three stopped working after their deployment. (Since that batch of satellites was experimental, Elon Musk had told reporters before the launch that failures were possible.)
Those three defunct satellites will circle the planet until Earth's gravity pulls them back towards the ground. As they fall into the atmosphere, they'll burn up, likely within a year. But until then, they'll stay in orbit with no way of communicating with operators on the ground.
"A 5% failure rate is actually better than most historical constellations, particularly for this size," Brian Weeden, a program director at the space sustainability organization Secure World Foundation, told Forbes. "But it is definitely not nearly good enough for a very large constellation of hundreds or thousands of satellites. The goal should be a failure rate of at least 1% or lower, and even that will lead to dozens of dead satellites."
Even SpaceX satellites that aren't dead have already caused collision problems: On September 2, the European Space Agency (ESA) revealed that it had to move its Aeolus satellite to avoid a possible collision with a SpaceX Starlink satellite.
SpaceX plans to start providing Starlink internet service in the US and Canada after six launches, sometime in 2020. It plans to have "near global coverage" in 2021.
But given the risks for telescope observations and space junk, some astronomers think that pace is too fast.
"I would prefer the licensing authorities required a slower phase-in so we can get experience with a 500-sat[ellite] constellation before going to 5,000 sats and so on," McDowell said on Twitter.
Dave Mosher contributed reporting to this post.