Artificial Luminosity: Enormous Satellite Rivals the Brightness of Only the Most Luminous Celestial Bodies

Satellite clusters, exemplified by the prototype known as BlueWalker 3, have sparked apprehensions among the astronomical community over potential interference with both nocturnal sky observations and radio astronomy. Striking a balance between meeting the demands of global communications and safeguarding astronomical investigations is essential. Source: AST SpaceMobile

Low Earth Orbit Telecommunication Satellites May Impede Astronomical Studies

The BlueWalker 3 prototype satellite, based on observations, ranks as one of the most luminous objects in the night sky, outclassing nearly all but the most brilliant stars.

Scientists in the field of astronomy warn that, without appropriate countermeasures, assemblies of these large satellites could inhibit our observational capabilities of celestial bodies and compromise radio astronomical studies.

Several corporations are in the planning stages of launching satellite ‘constellations,’ which could consist of hundreds of individual satellites intended to provide mobile or broadband connectivity across the globe.

The requirement for these satellites to operate in low-Earth orbit, coupled with their substantial dimensions, elevates concerns about their ability to disturb nighttime sky observations.

BlueWalker 3’s Trail over the Observatorio Astronomico Nacional, San Pedro Martir, Mexico, captured on November 12, 2022. Interruptions in the visual trail are a result of gaps between successive exposure frames that were combined to generate this visual. Source: I. Plauchu-Frayn

Consequences of BlueWalker 3 for Astronomy

An interdisciplinary group of researchers, led by experts from the IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (hosted jointly by NSF’s NOIRLab and the SKAO), and featuring scholars from Imperial College London, have disseminated a paper in the journal Nature. This paper evaluates the comprehensive impact of the BlueWalker 3 prototype on the field of astronomy.

Dr. Dave Clements, affiliated with the Department of Physics at Imperial College London, articulated, “The night sky serves as an unparalleled laboratory, facilitating scientific inquiries that are unfeasible within Earth-bound labs. Observations of the cosmos have yielded groundbreaking insights into fundamental physics and other domains at the frontier of human understanding, while also reshaping our collective perception of our position in the universe.”

Clements further noted that the untainted night sky constitutes an integral component of our collective cultural heritage and ought to be conserved for the benefit of society and future progeny.

Data Pertaining to BlueWalker 3

BlueWalker 3 was propelled into a low-Earth orbit on September 10, 2022, by AST SpaceMobile. It serves as a prototype for a planned fleet of more than one hundred analogous satellites aimed for use in mobile telecommunication. Observations conducted shortly after its launch indicated its high level of luminosity.

To gain a more thorough understanding of its implications for astronomy, the IAU and CPS initiated a global observation campaign. Contributions for this endeavor were received from multiple international locations, including Chile, the United States, Mexico, Aotearoa New Zealand, the Netherlands, and Morocco.

Data released subsequent to tracking BlueWalker 3’s luminosity over a 130-day duration revealed a sudden escalation in brightness following the complete deployment of its antenna array, measuring 64 square meters—the largest commercial antenna system ever to be launched into a low-Earth orbit.

Radio Frequency Interference Challenges

Beyond its impact on visible-light observations, BlueWalker 3 could potentially disrupt radio astronomical studies due to its use of wavelengths proximate to those utilized by radio telescopes. Even though some telescopes are situated within designated quiet radio zones, existing protective measures are not necessarily sufficient to guard against satellite-based transmissions.

Dr. Mike Peel, a co-leader at IAU CPS’s Sathub and a researcher in the Department of Physics at Imperial College, stated, “Radio frequencies emitted by BlueWalker 3 are perilously close to those allocated for radio astronomy. Current protective measures for observatories might be inadequate. Hence, more research is required to devise protective strategies for existing and future telescopic installations against the swarm of satellites scheduled for upcoming launches.”

Future Prospects

While recognizing the crucial role new satellite constellations play in enhancing global communications, the IAU and CPS underscore the need to assess their unintended consequences on astronomical studies carefully. Their deployment should be executed with meticulous consideration for their potential detrimental effects on our cosmic understanding.

Observations regarding BlueWalker 3 are slated to persist, with plans to examine its thermal emissions in the later part of this year. The subject will continue to be a point of discussion at the forthcoming IAU Symposium: Astronomy and Satellite Constellations: Pathways Forward, scheduled for October.

Reference: Article detailing the high optical brightness of BlueWalker 3, authored by a consortium of international researchers, published on October 2, 2023, in the journal Nature. DOI: 10.1038/s41586-023-06672-7

Frequently Asked Questions (FAQs) about BlueWalker 3 Impact on Astronomy

More about BlueWalker 3 Impact on Astronomy

• IAU Centre for the Protection of the Dark and Quiet Sky
• Imperial College London Department of Physics
• Nature Journal
• AST SpaceMobile
• NSF’s NOIRLab
• SKAO
• IAU Symposium: Astronomy and Satellite Constellations: Pathways Forward
• DOI for the Original Research