Astronomers are concerned about this satellite that is brighter than most stars

In 2022, Texas-based AST SpaceMobile launched the BlueWalker 3 satellite into space to provide transcontinental mobile phone service. But the ambitious project shined so brightly that it was among the 10 brightest objects in the sky, according to one study. A study published this week.

“The satellite would be among the 10 brightest objects if you count the stars and the Sun. It’s incredible,” said Siegfried Egel, co-author of the study. “I think it’s a byproduct of the fact that these environmental considerations have not been made in general.”

The new study quantifies the satellite’s brightness over a period of 130 days. Amateur and professional astronomers have recorded overhead passes from Chile, the United States, Mexico, New Zealand, the Netherlands and Morocco. The researchers evaluated the glow on a magnitude scale, with smaller numbers indicating brighter objects. For example, the North Star has a magnitude of plus two. The team found that BlueWalker 3 registered a brightness of +0.4.

The problem with the BlueWalker 3 satellite is its size. Its antenna array measures 64 square metres, the size of a squash court, and is the largest commercial antenna system ever deployed in low Earth orbit. The large antenna helps cell signals bounce back and forth across the globe; The larger the antenna, the better the call quality. But the antenna also reflects a lot of light back to Earth, making it appear very bright in the sky.

“Once they opened their antennas, they became 100 or more times brighter,” said Brad Young, an amateur astronomer at the Quiet and Dark Sky Conservation Center. “It has a significant increase in the area of ​​the antenna that reflects light.”

The extra light has many implications for astronomers, but also for non-scientists. Eagle said the light interferes with data collection. For example, satellite strips can mask near-Earth objects, such as an asteroid. A previous study by Eagle showed that 50% of near-Earth objects could be affected by these lines in the data.

It could also affect radio astronomy. Light pollution affects people’s circadian rhythms and the migration patterns of other animals.

Astronomers are already combating some of these problems using swarms of satellites, including SpaceX’s Starlink communications satellites. Thousands of Starlink satellites travel across the night sky in train formation, sometimes appearing as a UFO from another world. Each individual Starlink satellite is 10 times brighter than the astronomy community wants, Eagle said. SpaceX plans to launch 40,000 satellites.

But the BlueWalker satellite could quickly make conditions much worse. The fully extended satellite is six times larger and brighter than the Starlink satellite. With the latest launch as a prototype, AST SpaceMobile plans to send hundreds more into space. Some of them could be larger.

Even without the additional light, satellite streaming can pose a problem for other objects being launched. Collisions can produce a swarm of debris, which may impact or even damage other satellites in its path.

“As astronomers, we don’t want to be the takers of economic development or the takers of new developing countries that arrive as actors on the space stage,” said cosmologist Aparna Venkatesan, who was not involved in the new study. “But at the moment, the unstructured terrain means that we are not assessing the environmental impact, the impact of light pollution or many of the other consequences of this in systematic ways.”

The goal would be to bring companies together under a regulatory umbrella, where operators could share with each other their specifications, the brightness of the satellites, the film coatings they use, and other methods to darken their business, said Venkatesan, the University of San Francisco professor. Satellites.

Astronomer Fabio Falchi, who was not involved in the research, also called for strict regulation, but for bans, not mitigations. He says astronomers are too flexible in allowing companies to launch swarms of bright satellites, and he urged more astronomers to take a stand in a commentary article published in March.

“Disrupting the pristine state of the night sky is an intangible and unprecedented attack on the cultural heritage accumulated in the night sky,” Falchi, a researcher at the Institute for Light Pollution Science and Technology, wrote to the Washington Post. “Nowhere in the world will it be possible to see the starry sky without a satellite spoiling the experience.”