Astronomers have classified a new object among the brightest in the sky. It is not a star nor a planet: it is BlueWalker 3, the prototype of a new fleet of dozens of satellites that will provide a 5G connection from space. Achieving the technological challenge of being able to be connected anywhere on the planet is leading us to cross another frontier. After changing many landscapes and altering the climate of the entire planet, human civilization is also transforming the appearance of the night sky.
In the eyes of anyone, not just astronomers, looking at the sky began to look radically different in 2019. Then, Elon Musk’s SpaceX company began deploying Starlink, the largest of the so-called mega satellite constellations, which are putting new operators in orbit that offer global high-speed internet coverage (among them are amazon and OneWeb). Now these types of satellites have broken their brightness record, because according to a study published by the scientific journal Natureif we consider BlueWalker 3 a star, would be among the 10 brightestof the total of 9,096 stars that the human eye can distinguish with the naked eye.
The authors of the study warn that the current uncontrolled proliferation of these artificial stars is a risk for science: “All branches of observational astronomy can be affected. Despite the measures we are taking, these satellites can become confused with variable astronomical objects, or leave remains in our data that have unexpected repercussions,” says Meredith Rawls, who participated in the research from the University of Washington (USA). In addition, the astronomical community is beginning to study its environmental impact. Given the forecast that in a few years there will be hundreds of thousands of these satellites on the low earth orbitthere is concern that they contain materials that can trigger damage to the ozone layer.
For those who are interested in astronomy, these changes in the sky are a new element, which makes it more dynamic. The spectacle offered by a very dark night sky is no longer only starring stars and planets, which we see standing still above the celestial vault. Now we also see these satellites, which move, and that movement distinguishes them from the natural stars. As explained the astrophysicist Borja Tosar, In his introductory talks on astronomy, “satellites do not shine because they have their own light, but rather they reflect the light of the Sun. They are built with highly reflective materials and, therefore, even though they are so small (the Starlinks are like a washing machine, that deploys a solar panel the size of a motorhome) we see them as bright as a star millions of kilometers in radius, located several light years away.” Tosar stands out especially how Starlink satellite trains attract attention, which move in a line during their ascent to their final orbit at 550 kilometers altitude. “They arouse a lot of curiosity and, frequently, I receive reports from people who witness this phenomenon and believe they have seen a UFO,” adds this expert.
Astronomy apps for mobile phones, and also web pages like Heavens Aboveare used by amateurs and professionals to know precisely when satellite passes such as BlueWalker 3. This information is very useful both for those who go hunting for these artificial stars and for those who try to avoid them. Óscar Blanco plays that double role. He teaches how to identify them to visitors to the Trevinca Astronomical Center, which he directs in A Veiga (Ourense). And he manages to avoid the scratches that satellites leave in astrophotographs. These images take at least several seconds with the camera lens open, and that causes the moving dots of the satellites to become streaks that cross the sky.
“Fortunately, astrophotographers have computer programs that can erase these satellite traces. But to do this you need to take several images, and they cannot always be eliminated,” explains Blanco. The sleeplessness caused by the satellites—which in summer are visible almost all night and reach a considerable height above the horizon—gives a good idea of the interference that the new megaconstellations can pose for astronomical research.
From the Atacama Desert (Chile), Jeremy Tregloan-Reed dedicates himself to the study of exoplanets. He is one of the lead authors of the scientific paper on the glow of BlueWalker 3 and decided to investigate it “because there was talk that it would be the beginning of the end of astronomy, when it was deployed in November 2022. But the same thing was also said when we started to see the flashes of the Iridium satellites, at the end of the 20th century. ”.
‘BlueWalker 3’ and the end of astronomy
Tregloan-Reed maintains that overall, and at the moment, it doesn’t seem like a big problem. But it can become so, “if proliferation is not controlled and action is not taken to reduce the amount of sunlight reflected by satellites. The passage of a satellite with a brightness greater than the recommended limit of 7 could ruin an entire image of specific telescopes, such as that of the Vera C. Rubin Observatory [en construcción en el norte de Chile]”.
And according to the results of his recent research, BlueWalker 3 It reaches a brightness of magnitude 0.4. The figure may seem reassuring, but it is not: it implies that it is 437 times brighter than recommended. As Tregloan-Reed clarifies, the luminosity of celestial bodies is measured on an inverse scale: “The greater the brightness, the lower the magnitude number; and it is also a logarithmic scaleso decreasing five units means that the object will be 100 times brighter.”
Experts agree that the problem is not this specific device, but rather that by 2030 there are expected to be hundreds of thousands of satellites, launched by many different companies. BlueWalker 3which has broken records due to its gigantic 64 square meter antenna, is just a test for the new network of the operator AST SpaceMobile, which will have about 90 satellites up to seven times larger, called BlueBirds. This would make them at least as bright as Sirius, the brightest star in the sky.
“The look of the night sky could change forever. There is a risk that this view is dominated by moving satellites, rather than stars,” explains Mike Peel, from Imperial College London (United Kingdom), and also a participant in the research published by Nature. “To avoid this there is the general recommendation of the limit of magnitude 7, which implies a brightness so weak that it cannot be seen with the naked eye,” adds Peel.
The International Astronomical Union (IAU) has dedicated itself to this problem a symposium held in October on the Canary island of La Palma. The Spanish researcher David Galadi, member of the IAU commissions that study how satellite megaconstellations affect astronomy, highlights that at the La Palma scientific meeting the impact on the environment came to the fore: “There is considerable concern about the effect on the atmosphere from the increase in satellite launches; and also re-entries, since everything that goes up to low Earth orbit ends up falling again,” says Galadí.
Study the effects on the ozone layer
Maintaining these swarms of hundreds of thousands of satellites will mean that every now and then one will fall and disintegrate on its re-entry into the atmosphere, according to Galadí. “This will inject quantities of vaporized foreign substances, such as aluminum, into the upper layers of the atmosphere at a rate up to 10 times higher than the natural contribution from meteorites. And the formation of aluminum oxides can affect the ozone layer,” explains the researcher.
Given this theoretical possibility of damage to the ozone layer, explored in a communication from the La Palma symposium, Galadí points out the need for more research to quantify this impact. And he criticizes that the companies that launch satellite megaconstellations are not required to carry out these environmental impact studies in the upper layers of the atmosphere, in the absence of international regulations that regulate the use of low Earth orbit: “It is like the Wild West. “They are occupying a lawless territory and they can do whatever they want,” he adds.
While the investigation of this new type of environmental pollution is taking its first steps, the light pollution that this proliferation of satellites will bring is much more studied. Jeremy Tregloan-Reed warns that “even if all operators complied with the recommendation that their satellites have a maximum brightness of magnitude 7, and thus were not visible to the naked eye, they would contribute to increasing the background glow of the sky.” According to this researcher, this would erase from the sky the faintest stars that the human eye can detect, if the more than half a million satellites planned for 2030 become a reality. They confirm this risk the data from a recent study by the Spanish Salvador Barápublished in Nature Astronomy. And this effect will be more noticeable, precisely, in places that now have a darker sky, ideal for contemplating the stars.
For Meredith Rawls, this new form of light pollution is totally different from the usual one, from which we could escape by going to a location far from cities and towns. “However, satellites orbit around the entire planet. When all these megaconstellations are complete, there will be nowhere on Earth to escape to observe a dark, clean night sky,” Rawls laments.
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