BlueWalker 3: Satellites shine brighter than stars, and may eventually disappear

In our collective imagination, when we think about what the sky looks like at night, we imagine a long layer of dark velvet suspended above the ground. However, the night sky tends to become brighter and brighter.

In particular, the launch of the BlueWalker 3 satellite in 2022. Gradually, the latter has become one of the brightest objects in the sky, according to the conclusions of a study published on Tuesday, October 3 in the journal Science. nature.

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These latest observations add to the concerns expressed in the past by a number of specialists who have expressed concern about the challenges that await the astronomy sector: the launch of satellites, each brighter than the other, into low Earth orbits (OTB). It is a region of the Earth’s orbit extending to an altitude of up to 2000 km. It is located between the Van Allen belt and the atmosphere.

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Reflected sunlight

Sometimes, when satellites are in orbit around the Earth, they take the form of bright objects. As a result, they will reflect sunlight. Astronomers, satellite operators, and other “users” of the night sky are working on strategies to reduce brightness. However, as the number of satellites increases, this phenomenon threatens to derail space monitoring efforts.

Among the latest satellites to be launched into the night sky is BlueWalker 3. This prototype was launched just over a year ago now: September 10, 2022. It covers an area of ​​64.3 square meters, which means a relatively large reflection surface for our star’s light.

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An idea to take further into consideration?

To better understand the consequences of BlueWalker 3, an international team – made up of amateurs and professionals – conducted observations from Chile, the United States, Morocco, Mexico, New Zealand and the Netherlands.

Once this network was fully developed and deployed, it was found that the satellite in question was as luminous as Achernar and Procyon, the brightest stars in the constellations Eridanus And Canis Minoraccording to results published in the journal Nature.

These same observers reported that BlueWalker 3 periodically became hundreds of times brighter than the current International Astronomical Union recommendation requires. This regulation imposes the maximum brightness that satellites in low Earth orbit are supposed to comply with, in order to mitigate the effect of artificial interference.

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In their assessment, members of this international monitoring group recommended that the impact of satellites on the space and terrestrial environment be fully taken into account in the future launch authorization process.

Already last spring, scientists were alarmed by such light pollution in the journal Nature astronomy. They pointed out that the number of satellites in low Earth orbit has more than doubled since 2019, when the American company SpaceX launched the first “mega-constellation”, consisting of several thousand satellites.

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