For a detailed image from Earth, space is needed in places where as little disturbing light as possible disrupts the measurements. One such place is Chile’s Atacama Desert, where there are a number of telescopes. However, light reflected from satellites is now increasingly disrupting research work. Scientists show in the journal ‘Nature’ that the ‘BlueWalker 3’ satellite can shine up to a hundred times brighter than recommended by researchers.
The satellite in question was developed by the American company AST Space Mobile and launched into space on September 10, 2022. About two months later, the 64 square meter antenna of the prototype telecommunications satellite type was deployed in a near-Earth orbit, at an altitude of 500 to 600 kilometers, of which about 100 units will be in orbit in the future from there to serve the world with an additional broadband internet service.
One of the brightest objects in the night sky
“BlueWalker 3” has since been considered one of the brightest artificial objects in the night sky. A team of scientists and amateur astronomers wanted to know exactly how bright. To do this, they pointed large and small telescopes from Chile, the US, Mexico, New Zealand, the Netherlands and Morocco at the satellite. The current analysis by the team led by first author Sangeetha Nandakumar from the Universidad de Atacama (Chile) and Austrian astrophysicist Siegfried Eggl from the University of Illinois (USA) makes astonishing findings.
As a board member of the International Astronomical Union Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS), Eggl’s job is to determine the brightness of newly launched satellites regardless of the manufacturer’s information, explained the man of the interface between space travel and scientists researching astronomy. The problem with reflected sunlight from satellites is becoming increasingly virulent and is now causing problems for high-tech research with highly sensitive detectors, as well as for amateur stargazers.
Up to 40,000 satellites in orbit
“Since the company SpaceX launched thousands of ‘Starlink’ satellites, many ‘night owls’ have noticed this, especially shortly after the satellites launch when they move in a ‘string of pearls’ over the horizon. “But that’s just the beginning,” says Eggl. The current number of approximately 7,000 to 8,000 satellites in orbit will “increase to more than 40,000” due to SpaceX’s ambitions alone.
No fewer than twenty countries are currently planning to build their own internet access in space. Then there would be considerably more artificial celestial bodies in motion than visible stars. This becomes an even bigger problem for astronomers and others working in the radio frequency range, because here any satellite can appear as bright as the sun, Eggl explains. Because there are still no laws to protect the night sky, the IAU CPS is working with satellite operators to find a solution so that the reflections from the devices exceed the astronomical pain threshold of seven magnitudes (of values above seven: a satellite is no longer with the visible to the naked eye; note).
In any case, “BlueWalker 3” is well above this pain threshold: in its brightest phase during the observation period, the satellite reached a magnitude or “apparent brightness” of 0.4. This makes it as bright as Procyon and Achernar, the two brightest stars in the constellations “Little Dog” and “River Eridanus” respectively. In their article, the study authors recommend that a critical assessment of satellites’ impact on space and Earth’s environment should be part of pre-launch approval processes.
Source: Krone
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