Astronomers alarmed by BlueWalker 3 satellite that outshines all but seven stars

A prototype satellite for a proposed space-based cell phone community is brighter than all but seven stars within the evening sky. The satellite and others prefer it might pressure ground-based telescopes to both observe and dodge satellite trails or lengthen their observations to collect sufficient unspoilt information.

In 2022, Texas-based firm AST SpaceMobile put its BlueWalker 3 satellite into orbit to check the feasibility of a cell phone community orchestrated from area. Early observations of BlueWalker 3’s 64-square-metre reflective antenna advised it was brighter than most stars within the sky.

That has now been confirmed by a year-long monitoring marketing campaign utilizing telescopes within the US, Chile, the Netherlands and New Zealand. Siegfried Eggl on the International Astronomical Union in France and his colleagues have discovered that BlueWalker 3 is even brighter than earlier measurements and has the same brightness to the brightest stars within the constellations Canis Minor and Eridanus.

This presents a major menace to ground-based astronomy, says Eggl, particularly for wide-angle surveys of the evening sky, reminiscent of one that might be carried out on the Vera C. Rubin Observatory in Chile. (*3*) he says.

Some of this may be prevented if telescopes undertake monitoring and avoidance methods, but these strategies can nonetheless fail as a result of satellites are onerous to trace. This may imply that telescopes would wish to periodically shut down whereas a satellite strikes over their line of sight, probably delaying observations or skewing datasets.

Eggl and his crew additionally discovered that BlueWalker 3’s brightness fluctuated over time, relying on the angle, or angle, at which it confronted the solar. Companies like AST SpaceMobile have management over this angle, so that they play a major function in ensuring that the satellite displays minimal gentle, says Eggl.

In a press release, an AST SpaceMobile spokesperson stated it’s “collaborating with NASA and certain astronomy working groups to develop advanced industry solutions, including potential operational interventions.” It can also be avoiding broadcasts in areas delicate to radio astronomy, the spokesperson stated, in addition to controlling the satellite’s angle to minimise brightness and growing anti-reflective coatings for its subsequent technology of satellites, which it says will quantity round 90.

Many extra observations are wanted to work out the total extent of the influence on astronomy, particularly for longer wavelengths of sunshine, such because the radio band. Satellites like BlueWalker 3 are geared up with highly effective radio transmitters, so that they have the potential to do extra harm to radio-based astronomy, says Eggl. “For optical light, these things are as bright as the stars in the sky, but for radio astronomy, they can be as bright as the sun,” he says.

Comprehensive remark campaigns like this one are important, says Aparna Venkatesan on the University of San Francisco, California, as a result of “an individual satellite’s brightness is a complex, time-varying function of its design, area, viewing angle and altitude”.

“With ever more satellite launches planned by a rapidly rising number of state and private space actors, we must now consider not only the light pollution and electromagnetic interference from a diverse range of individual satellites, but the aggregate effects of all the satellite constellations slated for low Earth orbit,” she says.