Over the weekend, a “train” of 60 shiny Starlink satellites launched by the aerospace company SpaceX followed each other across the night sky, the first installment of a network of 12,000 satellites designed to bring satellite broadband to people on the surface of the planet. The sight, however, gave some astronomers pause, and many are worried that the sheer number of satellites will contaminate our views of space.
Loren Grush at The Verge reports that astronomers already have to contend with about 5,000 satellites orbiting Earth. To take an image of an object many, many light years away from the surface of the planet, astronomers need to expose their image for minutes or even hours. If a bright, shiny satellite zooms through the image, it can cause problems.
“It’s going to become increasingly likely that the satellites will pass through the field of view and essentially contaminate your view of the Universe,” Darren Baskill, physics and astronomy outreach officer at the University of Sussex tells Grush. “And it’s going to be really difficult to remove that contamination away from our observations.”
It’s not completely clear how bright the 500-pound Starlink satellites will be when they reach their final orbit. Nadia Drake at National Geographic reports that at first the satellites registered a brightness of magnitude 2, a tad bit dimmer than the North Star. But observations since the May 23 launch show that as the satellites slowly ascend to their orbital height of about 342 miles, the Starlinks have mostly dimmed to magnitude 5 to 7, but they can flare if sunlight hits them just right.
Cees Bassa, an astronomer at the Netherlands Institute for Radio Astronomy, tells Hannah Devlin at The Guardian that after analyzing the trajectory and brightness of the first 1,584 Starlink satellites scheduled for launch, about 15 satellites will be visible to the naked eye three to four hours after sunset. After all 12,000 satellites go into orbit, he estimates 70 to 100 will be visible all night during the summer.
It’s not just optical telescopes that could face problems. Radio telescopes, which observe radio waves coming from distant objects in the universe, could also face interference from the constellation of satellites, which use frequencies close to those studied by astronomers.
Starlink, for its part, is trying to fix or avoid some of these problems, reports National Geographic’s Drake. Indiana University astronomer Liese van Zee, who is also the chair of the National Academy of Science’s Committee on Radio Frequencies, says her committee is working on a coordination agreement with Starlink to limit radio interference, an arrangement similar to those made with other telecom companies that use satellites.
And over the weekend, in response to worries that the satellites were too bright, Musk affirmed on Twitter that his company was committed to science, and that he had instructed his team to look into lowering the albedo, or brightness, of the Starlink satellites. He also claimed that his team could tweak the orientation of the satellites when necessary to help out with any sensitive astronomy projects.
Astronomers already deal with satellites in their images and have techniques to compensate. In a tweet, Bruce Macintosh, an exoplanet researcher at Stanford University, said the new constellation of satellites is more of a “nuisance than a disaster.”
However, with other proposed projects getting off the ground, that nuisance will only grow. Another company, OneWeb, launched the first of 650 internet satellites in February, and Amazon recently announced it wants to deploy over 3,200 satellites for its own broadband project.