The Hubble Space Telescope, known for recording impressive images of the cosmos while advancing the field of astronomy, is under threat.

Private companies launch thousands of satellites that bombard the telescope, producing long light trails and light curves that may be impossible to remove. And the problem is only getting worse.

A study, published Thursday in the journal Nature Astronomy, reveals an increase in the percentage of images recorded by Hubble that are spoiled by passing satellites. And the data only goes to 2021. Thousands more satellites have been launched since then by SpaceX and other companies, and many more are expected to go into orbit in the coming years, affecting Hubble and potentially other telescopes in space.

“We will live with this problem. And astronomy will be impacted,” said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who was not involved in the study. “There will be science that cannot be done. There will be science that will cost a lot more to do. There will be things we will miss.

The legacy of the Hubble Space Telescope cannot be overstated. Thanks to the observatory, we now know, for example, that the universe is 13.8 billion years old, that most galaxies contain a supermassive black hole at their center, and that stars form in violent processes. Hubble’s images – including the magnificent clouds of gas and dust in the ‘Pillars of Creation’ and the sight of nearly 10,000 galaxies in the ‘Hubble Ultra Deep Field’ – never fail to inspire .

But the number of satellites in orbit has grown dramatically since Hubble launched in 1990, and now it’s looking at the cosmos through a field of satellites.

In May 2019, SpaceX launched its first batch of Starlink satellites, designed to broadcast internet signals around the world. Soon after, an outcry erupted among astronomers who feared the Starlink footage would jeopardize a number of campaigns to observe the universe from telescopes on Earth.

In response, Elon Musk, founder and CEO of SpaceX, suggested that astronomers get around the problem by moving telescopes into orbit.

But Hubble, which lives in low Earth orbit about 335 miles above the Earth’s surface, actually resides less than 10 miles below most Starlink satellites. This means that the observatory and other orbiting space telescopes still face interference from satellite constellations. “Not only do you have to place your telescopes in space, but you also have to place them above all other traffic,” Dr. McDowell said.

“I think we will be forced to do this in the decades to come,” he said. But that’s not possible for today’s low-Earth-orbit telescopes or spacecraft that governments are building and launching in years to come.

To quantify the effect of satellite constellations on Hubble, Sandor Kruk, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany, and his colleagues analyzed an archive of images taken from 2002 to 2021.

They had the help of hundreds of citizen scientists who scoured the images to mark those with clear satellite streaks. This dataset was then used as a training set for a machine learning algorithm that analyzed over 100,000 individual Hubble photos. Their results show that the probability of seeing a satellite in a Hubble image from 2009 to 2020 is only 3.7%. But the chance of seeing one in 2021 is 5.9% – an increase they say matches Starlink. As of the date of the analysis, 1,562 Starlink satellites were in orbit. Another company, OneWeb, had launched 320 satellites.

Mark McCaughrean, an astronomer at the European Space Agency and co-author of the new study, is confident in their analysis, but notes that this is only a minor issue at the moment. Typically, Hubble takes multiple images stacked on top of each other – a technique that wipes out all satellites.

And NASA agrees. “Although such analyzes may show a gradual increase in detected satellite trails over time, most of these trails are easily removed using standard data reduction techniques, and the majority of affected images are still usable. “, a spokeswoman said of the latest study. “Satellite footage does not currently pose a significant threat to scientific efficiency and analysis of Hubble data.”

This threat is higher when Hubble is monitoring a wide swath of sky. Then he can take only one or two images before redirecting his camera. If a satellite bombards one of these images, the image may need to be discarded.

Additionally, satellites could pose a serious threat to a telescope that has yet to be launched. At the end of this year, China plans to send Xuntian, also known as the Chinese Space Telescope, into low Earth orbit. Xuntian will have a wider field of view than Hubble, which will make it much more difficult for satellites to pass undetected.

“He’s going to be very badly affected by these satellites right off the bat,” Dr McDowell said.

And Xuntian can’t just launch into a higher orbit. China’s plan is for the telescope to share an orbit with the Tiangong space station so that astronauts can refurbish it if needed.

A SpaceX spokesperson declined to comment on the new study, but pointed to the company’s past efforts to mitigate the effects of Starlink. The company has tried various methods to darken its satellites, including mirror film designed to direct light away from the ground. But Meg Schwamb, a planetary scientist from Queen’s University Belfast who was not involved in the study, fears the light may be directed upwards and could potentially make things worse for space telescopes.

There are simply too many unknowns right now, including the ultimate number of satellites.

SpaceX hopes to eventually expand the size of its fleet to 42,000 Starlink satellites. Many other companies are also in the market: Amazon, UK satellite provider OneWeb, a Chinese company called Galaxy Space and even governments. A total of 431,713 satellites are expected to be launched in the coming years.

“It’s a bit of a feeding frenzy right now,” Dr. McCaughrean said.

This estimate is based on documents filed with the US Federal Communications Commission and the International Telecommunication Union. But even if just 100,000 satellites were launched, it would increase the number of satellites in orbit by a factor of 10 since the new study, meaning around 50% of Hubble’s images would spot a satellite. And if all the other images had satellite footage, researchers worry about the amount of usable scientific data that could be collected.

“When will Hubble no longer be useful?” asked Dr. McCaughrean. “It could be 10 or 20 years from now, but it’s not inconceivable that there will be a time when you say, ‘Don’t bother us anymore. “”