Thursday, July 22, 2021

What are these tracks in Orion?

They are reflections of sunlight from various Earth-orbiting satellites. Appearing to the naked eye as a series of successive dots floating in the twilight sky, the growing number of communication satellites, including the SpaceX Starlink satellites, is causing concern among many astronomers. On the positive side, Starlink and similar constellations make the post-sunset sky more dynamic, global satellite-based communications are faster and help provide digital services to rural areas that are currently underserved.

On the downside, however, these low-Earth orbiting satellites make some deep astronomical imaging programs more difficult, in particular observational programs that need images taken just after sunset and before dawn. Future sets of planned satellites operating in higher orbits could impact deep-universe investigations planned for large ground-based telescopes anytime during the night. The bands in Orion are not from Starlink, but from satellites in high geosynchronous orbit. The picture shown, taken in December 2019, is a digital combination of over 65 3-minute exposures, with some images taken to highlight the Orion nebula in the background, while others show satellites passing by. 

(2021 June 1st)Image credit: Amir H. Abolfath

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