How Starlink satellites are ‘blinding’ astronomers

At the same time, they also create “radio noise”, or unintended electromagnetic radiation (UEMR). This is what impedes the work of radio astronomers observing the sky from Earth.

Why radio astronomy matters

Radio astronomy is a branch of astronomy that studies celestial objects at radio frequencies. Unlike optical telescopes that detect visible light, radio telescopes are designed to detect radio waves (which have higher wavelengths and lower frequencies) emitted by objects in space. But just like bright visible light can blind the observer — like the bright headlights of an approaching car — the same can also happen at radio frequencies. This is essentially why radio noise is a problem.

For radio astronomers, observing while a satellite is in its field of view is like trying to see the faintest star visible to the naked eye next to a full Moon, Cees Bassa of the Netherlands Institute for Radio Astronomy (ASTRON) and the lead author of the recent study, told Science Adviser.

Benjamin Winkel, a scientist at the Max Planck Institute for Radio Astronomy who contributed to the study, said the interference is literally “blinding” scientists. “When we say ‘blinded’ it means your eye collects too much light for you to see anything, you are getting saturated. This is exactly what happens with our radio telescopes,” he told DW.

What Starlink does to space communications

Things might get worse. The recent study found that Starlink’s second-generation satellites — which currently account for less than a third of the network — emit UEMR at levels 32 times brighter than its first-generation satellites. This is despite Starlink already running into trouble about the UEMR of its first-gen satellites.

“While the generation 1 satellites indeed got dimmer in the last year — so Starlink actually did something to them [to reduce radio leaks] — the new generation unfortunately seem to be brighter again,” said Winkel.

Moreover, as launching satellites becomes cheaper, some estimate that as many as 100,000 satellites could be orbiting Earth by 2030. The number was pegged at 11,330 in June 2023 by the United Nations Office for Outer Space Affairs (UNOOSA).

Experts say that these developments signal the need for regulations for satellite operators, just like there exist regulations for radio pollution from ground-based electronic sources like cellphone towers. “There is no way to make any electrical or electronic apparatus without this kind of leakage… the question always asked is: how much is leaked?” Winkel said. This is what regulations can help minimise.

Currently, astronomers are largely reliant on forging good faith interactions with companies like Starlink, which put satellites into space.