The recent large scale deployment of the first piece of the SpaceX satellite constellation triggered a controversy among astronomers and astro-photographers. With the planned launch of 12,000 satellites by the mid-2020s, some people fear the worst. What is really going on?

The Starlink concept is simple: inject thousands of satellite in low earth orbit to create a space-based Internet communication system that will provide worldwide coverage anywhere on the planet. Unfortunately, regular star observer knows that orbiting satellites can become visible when they reflect the sunlight back to earth. The observability of a satellite depends of several factors such as the size and nature of the object, the angle of the sunlight in relation to the ground, the orientation of the solar panels of the spacecraft, the distance from earth, and the time of the day. But with 12,000 satellites scheduled for lift-off, several astronomers are concerned about the potential light pollution that could be caused by the Starlink constellation. Astro-photographers could also be impacted since this type of imagery requires long exposure and having thousands of artificial stars crisscrossing the sky at any moment may not be helpful.

Bill Kell, an astronomy professor at the University of Alabama says: “I saw a pass of the Starlink Train about 15 degrees from zenith over Tuscaloosa. Some of them showed very systematic flaring, flashing brightly at nearly the same location in the sky. The brightest flares reached a magnitude of 2 for about 5 seconds.” "For reference, that’s 50% brighter than Sirius, the brightest star in the sky" explains space weather archive.

Elon Musk initially discarded the concerns but he finally asked his engineers to reduce the albedo of the satellites (decrease the light reflection).

There are already 4900 satellites in orbit, which people notice ~0% of the time. Starlink won’t be seen by anyone unless looking very carefully & will have ~0% impact on advancements in astronomy. We need to move telelscopes to orbit anyway. Atmospheric attenuation is terrible. pic.twitter.com/OuWYfNmw0D — Elon Musk (@elonmusk) May 27, 2019

Agreed, sent a note to Starlink team last week specifically regarding albedo reduction. We’ll get a better sense of value of this when satellites have raised orbits & arrays are tracking to sun. — Elon Musk (@elonmusk) May 27, 2019

However, as the satellites are gaining altitude, they should be less visible. For Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics: “It’ll be weeks or months before we can fully assess the situation.”

In any case, if this concern is justified, M. Musk promised that his team will "make sure Starlink has no material effect on discoveries in astronomy. We care a great deal about science."

Cover Photo by SpaceX on Unsplash.