Astronomers are expressing concerns over the plans of Elon Musk’s Space X to launch up to 42,000 satellites in a mega-constellation called Starlink. So far only 122 have been deployed — and astronomers are already reporting unwanted impacts.

With over 2,000 now active and orbiting Earth, satellites are key to modern life. Telecommunication satellites support mobile phone signals and mobile internet. As 5G services start to be deployed, a new set of satellites with the proper technology will need to be launched.

A recent incident with SpaceX raised concerns among astronomers over the consequences of Elon Musk’s plan. The 122 satellites launched by Starlink are brighter than most of the stars visible to the human eye and also move faster through the sky. This leaves a trail that can pollute astronomer’s data.

A group of 19 satellites of Starlink passed on November 18th near the Cerro Tololo Inter-American Observatory’s site in Chile. It lasted for five minutes and it affected an image taken by the Dark Energy Camera (DECam). The image shows the satellite train entering into the camera’s vision.

“Wow!! I am in shock,” wrote CTIO astronomer Clara Martinez-Vazquez on Twitter.

Satellites are usually dark in the night sky, but sunlight can reach them right after the Sun goes down or early in the morning when the sky is black, making them visible through telescopes of binoculars.

The number of Starlink satellites already launched represents only 0.3% of those proposed, so the consequences for astronomers could be worst. Looking for faint objects, which is the main goal of observatories seeking objects that could harm Earth, would be hindered, astronomers claim.

Starlink’s satellites are located in elevations of over 1,000 km, which means their orbital decay would take millennia. This can create problems with other types of satellites. For example, in September, a satellite used for Earth observation was close to crashing with a Starlink satellite. “A full constellation of Starlink satellites will likely mean the end of Earth-based microwave-radio telescopes able to scan the heavens for faint radio objects,” Swinburne University astronomer Alan Duffy told ScienceAlert in May after the first launch of Starlink satellites.

The criticism of astronomers to Starlink’s plans was dismissed by Elon Musk and SpaceX, who claimed their satellites would have a minor impact on astronomy. They said SpaceX is working on reducing the albedo of the satellites and that Starlink would adjust the satellites on-demand for astronomical experiments.

Cees Bassa from the Netherlands Institute for Radio Astronomy claims that up to 140 satellites of Starlink will be visible all times from observatories on Earth. But the difficulties could be overcome if the companies implemented some changes, according to Bassa.

Bassa suggested placing a moratorium on the launch of new satellites of Starlink until doing modifications, as well as also deorbiting the current satellites. He also said the company should redesign the satellites to reduce their reflectivity and should provide real-time information on their trajectory plans.