Jan 18, 2022 - Science

Study: SpaceX Starlink satellites seen streaking through astronomy images

The Andromeda Galaxy with a Starlink streak crossing it.

The Andromeda Galaxy with a Starlink streak crossing it. Photo: Caltech/ZTF

Twilight images taken by a telescope in California increasingly have streaks from satellites in them, according to a new study examining the effect of SpaceX's Starlink satellites on the night sky.

Why it matters: SpaceX has launched hundreds of internet-beaming satellites to orbit in recent years, stoking fears from some scientists that the small, relatively low-orbiting satellites could make astronomy harder.

  • The Elon Musk-founded company is planning to launch another clutch of 49 Starlink satellites tonight at 7:04pm ET.

What they found: The new study, in The Astrophysical Journal Letters, found that 5,301 streaks from Starlink satellites popped up in photos taken by the Zwicky Transient Facility near San Diego from November 2019 to September 2021.

  • That's an increase from 0.5% of twilight images being affected in 2019 to nearly 20%.
  • The team behind the study found the Starlink streaks mostly appeared in twilight images, which are key to finding potentially dangerous asteroids and comets that come from the same part of the sky as the Sun.
  • "We don't expect Starlink satellites to affect non-twilight images, but if the satellite constellation of other companies goes into higher orbits, this could cause problems for non-twilight observations," Przemek Mróz, one of the authors of the new study, said in a statement.
  • If SpaceX does eventually manage to create a constellation of about 10,000 satellites, the authors of the study expect every twilight image taken by the ZTF to have a streak from a Starlink satellite in it.

But, but, but: Those satellite streaks may not actually matter all that much for scientific observations with the telescope.

  • "There is a small chance that we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF," Tom Prince, another author of the study, said.
  • However, other observatories, like the Vera Rubin Observatory — expected to start science operations next year — could have more outsized effects from Starlink due to its sensitive optics.
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