Astronomers alarmed by satellite that outshines all but 7 stars
Path of BlueWalker 3 crossing the night sky, taken from a yard in Tucson, Arizona
A. Block/IAU CPS
A prototype satellite for a proposed space-based mobile cellphone network is brighter than all but seven stars in the night sky. The satellite and other folks like it could pressure floor-dependent telescopes to either keep track of and dodge satellite trails or extend their observations to collect adequate unspoilt facts.
In 2022, Texas-primarily based firm AST SpaceMobile put its BlueWalker 3 satellite into orbit to check the feasibility of a cell cell phone community orchestrated from area. Early observations of BlueWalker 3’s 64-sq.-metre reflective antenna recommended it was brighter than most stars in the sky.
That has now been confirmed by a yr-very long checking marketing campaign utilizing telescopes in the US, Chile, the Netherlands and New Zealand. Siegfried Eggl at the International Astronomical Union in France and his colleagues have uncovered that BlueWalker 3 is even brighter than former measurements and has a identical brightness to the brightest stars in the constellations Canis Minor and Eridanus.
This offers a substantial risk to floor-dependent astronomy, says Eggl, primarily for vast-angle surveys of the night sky, these types of as 1 that will be carried out at the Vera C. Rubin Observatory in Chile. “If there’s a bunch of these actually brilliant objects, I consider the danger is that there is going to be likely significant-scale knowledge reduction, if not damage to detectors, if that is not mitigated,” he says.
Some of this may possibly be avoided if telescopes adopt monitoring and avoidance strategies, but these techniques can even now are unsuccessful mainly because satellites are difficult to observe. This may possibly necessarily mean that telescopes would need to have to periodically shut down when a satellite moves above their line of sight, likely delaying observations or skewing datasets.
Eggl and his group also uncovered that BlueWalker 3’s brightness fluctuated above time, dependent on the perspective, or angle, at which it faced the sunshine. Organizations like AST SpaceMobile have handle about this angle, so they engage in a considerable job in producing certain that the satellite reflects minimum mild, claims Eggl.
In a statement, an AST SpaceMobile spokesperson mentioned it is “collaborating with NASA and selected astronomy operating teams to produce highly developed sector solutions, together with opportunity operational interventions.” It is also keeping away from broadcasts in places delicate to radio astronomy, the spokesperson claimed, as very well as controlling the satellite’s mind-set to minimise brightness and producing anti-reflective coatings for its upcoming generation of satellites, which it states will selection about 90.
Many much more observations are required to operate out the full extent of the affect on astronomy, particularly for more time wavelengths of light, this sort of as the radio band. Satellites like BlueWalker 3 are outfitted with impressive radio transmitters, so they have the possible to do a lot more harm to radio-based mostly astronomy, suggests Eggl. “For optical light-weight, these issues are as vibrant as the stars in the sky, but for radio astronomy, they can be as vibrant as the sunshine,” he claims.
In depth observation strategies like this a single are important, says Aparna Venkatesan at the University of San Francisco, California, because “an individual satellite’s brightness is a complex, time-various function of its design, region, viewing angle and altitude”.
“With at any time much more satellite launches planned by a rapidly increasing amount of state and non-public room actors, we have to now take into account not only the light-weight air pollution and electromagnetic interference from a diverse variety of particular person satellites, but the mixture effects of all the satellite constellations slated for lower Earth orbit,” she suggests.
