American satellite raises concerns for being brighter than 99.8% of stars in the sky

BlueWalker 3 Experimental Satellite with a Massive 64m² Reflective Antenna Causes Astronomical Observation Challenges.

BlueWalker 3, a satellite from the American company AST SpaceMobile, is brighter than 99.8% of the stars visible to the naked eye, according to a report by New Scientist on November 26. Launched in September, BlueWalker 3 aims to test a mobile connectivity technology, including 4G or 5G Internet, directly from the satellite to mobile phones, providing coverage to remote areas.

The 64m² reflective antenna of the BlueWalker 3 satellite after deployment in orbit. (Photo: AST SpaceMobile)

According to plans, AST SpaceMobile will launch an additional 100 satellites named Bluebird. The CEO of AST SpaceMobile, Abel Avellan, stated that the Bluebird satellites may be twice the size of BlueWalker 3, making them even brighter.

Astronomers are concerned that BlueWalker 3, with its 64m² reflective antenna and the Bluebird satellites, could interfere with astronomical observations by creating bright streaks in images captured by ground-based telescopes.

In the 64 days following the launch of BlueWalker 3, astronomer Anthony Mallama and his colleagues monitored its brightness from Earth, using binoculars to observe the experimental satellite and compare it with known stars. At the time of its strongest reflection—during sunrise and sunset—they noted it reached a brightness level of +1.5 on the apparent magnitude scale (the smaller the number, the brighter the object).

“Only 14 stars in the night sky are brighter than +1.5. This means that under typical conditions, BlueWalker 3 is brighter than 99.8% of the stars visible to the naked eye“, said John Barentine from the American company Dark Sky Consulting.

The reflection of Bluebird at dawn and dusk could alter the sky for stargazers and affect cultural events that rely on stars and constellations visible at these times, according to expert Aparna Venkatesan from the University of San Francisco, California. “Eventually, these satellites will appear at higher altitudes, above the horizon, and will be visible for longer periods as they reach their planned higher orbits”, she stated.

“We aim to use the latest technologies and strategies to minimize the impact on astronomy. We are actively working with experts on the latest improvements, including anti-reflective materials”, a spokesperson from AST SpaceMobile said.