“The astronomy community was not ready for this, and certainly not funded for it,” said Tony Tyson, chief scientist at the Rubin Observatory.
SpaceX did not respond to requests for comment.
Starlink is a satellite-based Internet constellation intended to cover the planet in high-speed broadband, and is often touted as a way to bring connectivity to billions of people who still lack reliable Internet access. The idea requires swarms of satellites operating in low Earth orbit, about 340 miles high, in the case of SpaceX, to provide continuous coverage.
Other companies have tried and failed to build such an internet constellation for decades. But SpaceX is already launching new satellites at an unprecedented rate. More than 400 Starlink satellites have been deployed since January, and SpaceX plans to grow Starlink to include more than 40,000 satellites. That’s five times the total number of satellites that humans have launched since the dawn of space flight.
There are no formal rules that regulate the brightness of new satellites. And a host of other companies, including Amazon and OneWeb, are building, or plan to build, Starlink-like satellite internet constellations.
Tyson said SpaceX deserves credit for making a sincere effort to mitigate the problems that these satellites will pose to astronomers.
But the question academics, experts, and other stakeholders are now asking is: How permanently and severely will the commercial space race alter the night sky?
“I am always optimistic,” Tyson told CNN Business. “But frankly, I’m scared.”
SpaceX vs. astronomy
From the moment SpaceX launched its first batch of 60 Starlink satellites into Earth’s orbit last year, alarms have sounded for people who spend time studying the sky.
Astronomers captured what looked like traces of glowing ants crawling through telescopic lenses. Some amateur astronomers had fun. But for a cohort of professional astronomers, it was horrible. Many aired their complaints on social media.
At first, SpaceX CEO Musk was on the defensive.
Starlink satellites “will not be seen by anyone unless you look very carefully,” and they will not have a “significant impact on advances in astronomy,” Musk said in a May 2019 tweet.
But that was not true. Astronomers discovered that the Starlink satellites’ rather large size (573 pounds or 260 kg) and their low altitude made them appear particularly bright from the ground. They can even be seen without a telescope in some areas. If the Starlink constellation grows to include thousands of satellites, “they will potentially outnumber all visible stars in the sky,” said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who studied the subject.
SpaceX quietly started working with the astronomy community last year and tried various methods to reduce the brightness of the satellite.
Those efforts, detailed in a recent blog post, include tilting satellites to avoid the sun’s rays. SpaceX also said that each of the 57 Starlink satellites to be launched on its next mission, scheduled for this month, will be equipped with a retractable visor.
“SpaceX is committed to making future satellite designs as dark as possible,” SpaceX said in its blog post, which spanned 2,900 words.
But even at best, Starlink satellites could significantly harm astronomers’ ability to study the sky.
Magnitude 7
SpaceX acknowledged in its blog post that Starlink satellites pose a particularly apparent problem for the Rubin Observatory, a $ 500 million telescope funded by the US National Science Foundation, the Department of Energy, and private donations. It is named after the late astronomer Vera Rubin, who provided some of the first evidence for the existence of dark matter.
The observatory, which looks like a robotic snail perched on a mountain in Chile, will capture 1,000 images every night starting in 2022.
Unlike other telescopes, the Rubin Observatory will be able to photograph the entire sky in just three nights. And when the survey is complete, it will create an unprecedented “cinematic view of the cosmos,” according to the Association of Universities for Research in Astronomy. That will give scientists an unprecedented opportunity to study everything from the origins of the universe to the unknown contents of the Milky Way.
It could prove the existence of Planet 9, which some scientists predict is a world larger than Earth, that could be responsible for the inexplicable movement of other objects in the far reaches of our solar system. If Planet 9 is out there, it could reshape theories about how our solar system was created, wrote astronomer and journalist Stuart Clark in an article published this week.
The Rubin Observatory will also be particularly useful for tracking near-Earth asteroids that may one day threaten our planet. Those observations could be further damaged by satellite interference. Astronomers often search for asteroids at twilight, at the same time of day that Starlink satellites appear brightest, Tyson said.
The size and sensitivity of the Rubin Observatory telescope also make it more vulnerable to light pollution from Starlink. The observatory’s camera lens is “infinitely focused” to capture distant celestial bodies, Tyson said. That means that objects in the foreground, such as bright satellites in low Earth orbit, appear out of focus, creating an enlarged light blur.
Scholars who studied the issue made it clear in May: “If not controlled,” reads an executive summary from the Rubin Observatory, Starlink and other similar satellites, “they could jeopardize the early discoveries of the Rubin Observatory.”
The study suggested that SpaceX would need to darken its satellites to 7th magnitude.
Magnitude is a measure of brightness in which higher numbers signify a fainter appearance. For example, Neptune has an apparent magnitude of about 7.7. Most Starlink satellites already in orbit are much brighter than that. Even a dark-coated experimental satellite that SpaceX launched in January was still twice as bright as the seventh magnitude.
It is still unclear whether the visors SpaceX developed for the new satellites will reduce their brightness to that level. Astronomers have not had a chance to observe a satellite that the viewer tested, which SpaceX launched in April, said Meredith Rawls, an astronomer who co-authored the study.
Due to the Covid-19 pandemic, many observatories are closed.
The terrifying part, Rawls added, is that even if SpaceX can dim Starlink satellites to 7th magnitude, it will still affect data from the Rubin Observatory. Lost pixels would correlate with “several months of observation time,” according to the study that Rawls co-authored.
And the more the satellites interfere, the more likely it is that astronomers will make a mistake or come to an inaccurate conclusion. Making sure that doesn’t happen will require finding better ways to clean up faulty images, and that takes time and money.
“There is no clear mechanism to finance that work,” Rawls said. “There are no longer enough funds for all the great science that astronomers would like to do.”
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