How Dark is Darksat? (Not Very)

Feb. 25, 2020: Last November, SpaceX tried to save astronomy. Among 60 bright and shiny Starlink satellites that blasted off from Cape Canaveral on Nov. 11, 2019, was one “Darksat”–a Starlink satellite with an experimental anti-reflective coating. Making Starlink satellites darker could head off a brewing confrontation between astronomers and internet entrepreneurs.

“But is ‘Darksat’ really darker?” asks astrophotographer Thierry Legault. “On Saturday morning at astronomical twilight, I filmed the passage of a group of Starlink satellites at their final altitude (550 km). Darksat is one of the brightest.”

Thierry-Legault-starlink_20200222_constellations_fb_1582484902

“On the images covering more than 80° on the sky (from Lyra to Bootes), these satellites reached magnitude 2.5, which is even brighter than I expected! We are still waiting for effective albedo reduction measures, and in the meantime the launches continue…” he says.

Indeed, SpaceX has conducted three more launches since last November, bringing the total number of Starlink satellites in orbit to 300. Ultimately, the network of internet satellites could grow as large as 42,000. That’s a lot of artificial stars–and so far the Darksat experiment has not succeeded in reducing their visibility. Keep trying, SpaceX.

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