In the ever-evolving realm of technology, we find ourselves continuously pushing the boundaries of innovation. One such innovation that has captured the world’s attention is the advent of massive satellites that shine brighter than even the most radiant stars in our night sky. These manmade celestial bodies are a testament to human ingenuity, but they also raise important questions and concerns. In this article, we delve into the world of massive satellites, their impact on our night sky, and the potential threats they pose.
Massive Low Earth Orbit Communications Satellites Could Disrupt Astronomy
The BlueWalker 3 prototype satellite has been observed to be one of the brightest objects in the night sky, glowing brighter than all except the stars.
Trails in the night sky left by BlueWalker 3 over the Observatorio Astronomico Nacional, San Pedro Martir, Mexico, observed on November 12, 2022. The breaks in the trail are caused by breaks between the exposures that were stacked to create this image. Credit: I. Plauchu-Frayn
The capacity to watch the stars from Earth and conduct radio astronomy may be interfered with if groupings of enormous satellites are not mitigated, according to astronomers.A number of businesses are developing satellite “constellations,” which are collections of perhaps hundreds of satellites that can bring mobile or internet services anywhere in the world.However, because these satellites must be in ‘low-Earth’ orbit and have a huge maximum size, it is possible that they will interfere with night-sky studies.
Impact of BlueWalker 3 on Astronomy
A paper evaluating the specific effects of the prototype BlueWalker 3 satellite on astronomy has now been published in Nature by an international team of scientists led by astronomers from the IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS, co-hosted by NSF’s NOIRLab and the SKAO).
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An image of the 8 meter x 8 meter BlueWalker 3 satellite as seen from the ground. Credit: M. Tzukran
“The night sky is a unique laboratory that allows scientists to conduct experiments that cannot be done in terrestrial laboratories,” stated Dr. Dave Clements of the Department of Physics at Imperial. Astronomical observations have altered human perceptions of our place in the cosmos and given us new insights into fundamental physics and other fields of inquiry at the frontiers of our knowledge.
“The pristine night sky is also an important part of humanity’s shared cultural heritage and should be protected for society at large and for future generations.”
Observational Data on BlueWalker 3
On September 10, 2022, AST SpaceMobile launched BlueWalker 3 into low-Earth orbit as the first satellite in a constellation of more than a hundred similar ones that would be used for mobile communications. The satellite was one of the brightest objects in the sky, according to observations made just a few weeks after launch.
However, the CPS started an international observing campaign to better understand its effects on astronomy. Professional and amateur observations from locations in Chile, the US, Mexico, Aotearoa New Zealand, the Netherlands, and Morocco were included in this endeavour.
The recently made public data show a dramatic rise in brightness for BlueWalker 3 that coincides with the antenna array’s full unfolding. At 64 square metres, the antenna array is the largest commercial antenna system ever put into low-Earth orbit.
The BlueWalker 3 satellite captured on April 3, 2023. The optical brightness of the 8 meter x 8 meter satellite — one of the brightest objects in the night sky having reached a peak brightness of magnitude 0.4 — is exhibited here as it travels across the starry backdrop. For comparison, two fainter satellites can also be seen in the footage; Starlink-4781 (in front of BlueWalker) and Starlink-4016 (paralell and slightly behind BlueWalker in a few frames). Credit: Delft Technical University/M. Langbroek
The satellite’s trajectory over time was calculated using a portion of the observations. The authors were able to assess the accuracy of predictions and how this can change due to factors like atmospheric drag by comparing the anticipated path with the observations made.
Astronomers should be aware of the satellites’ positions so they can attempt to avoid them or at least know where they will appear in the data. Beyond hiding their position and erasing data for that region of the sky, it is challenging to mitigate the brightness.
Radio Interference Issues
BlueWalker 3 could obstruct not just visual observations but also radio astronomy because it observes at wavelengths that are near those used by radio observatories. Despite the fact that certain telescopes are situated in radio silent zones, they are not necessarily shielded from satellite broadcast because the regulations in place to safeguard these areas now only apply to terrestrial transmitters.
“BlueWalker 3 actively transmits at radio frequencies that are close to bands reserved for radio astronomy, and existing observatory protections from radio interference may not be sufficient,” said Dr. Mike Peel, co-lead of the IAU CPS’s Sathub and researcher in the Department of Physics at Imperial. Therefore, more study is necessary to develop methods for shielding current and future telescopes from the numerous satellites scheduled for deployment over the next
Looking Ahead
The new satellite constellations are acknowledged as playing a significant role in enhancing global communications by the IAU and CPS partners. However, they could seriously impede the development of our understanding of the universe by interfering with astronomical data. Therefore, their deployment should be carried out while giving proper regard to their adverse effects and making an effort to lessen their impact on astronomy.
Astronomers will continue to monitor BlueWalker 3 and have plans to observe its thermal emission later this year. At the next IAU Symposium: Astronomy and Satellite Constellations: Pathways Forward in October, astronomers will continue their conversation on this subject.
Reference: “The high optical brightness of the BlueWalker 3 satellite” by Sangeetha Nandakumar, Siegfried Eggl, Jeremy Tregloan-Reed, Christian Adam, Jasmine Anderson-Baldwin, Michele T. Bannister, Adam Battle, Zouhair Benkhaldoun, Tanner Campbell, J. P. Colque, Guillermo Damke, Ilse Plauchu Frayn, Mourad Ghachoui, Pedro F. Guillen, Aziz Ettahar Kaeouach, Harrison R. Krantz, Marco Langbroek, Nicholas Rattenbury, Vishnu Reddy, Ryan Ridden-Harper, Brad Young, Eduardo Unda-Sanzana, Alan M. Watson, Constance E. Walker, John C. Barentine, Piero Benvenuti, Federico Di Vruno, Mike W. Peel, Meredith L. Rawls, Cees Bassa, Catalina Flores-Quintana, Pablo García, Sam Kim, Penélope Longa-Peña, Edgar Ortiz, Ángel Otarola, María Romero-Colmenares, Pedro Sanhueza, Giorgio Siringo and Mario Soto, 2 October 2023, Nature.
DOI: 10.1038/s41586-023-06672-7
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