Astronomy Report Says Private Satellites Will Diminish Night Sky

simulations show satellite-free night skies could become rare

By Jonny Lupsha, Wondrium Staff Writer

A new report published by NOIRLabs says SpaceX and OneWeb will cause problems for the night sky. The Elon Musk-owned space program launched 60 satellites in May 2019. Several computer simulations projecting their orbits show that they may crowd the sky, diminishing Earth-based astronomy. Many factors affect stargazing already.

Woman sitting stargazing
Stargazing has long been affected by weather conditions and light pollution, and now by prolific numbers of man-made satellites. Photo By varuna / Shutterstock

According to a report by NOIRLabs, the sky may soon look more crowded than most of us would expect. “Initial visibility simulations have shown the significant negative impacts expected from two communications-focused low-Earth orbit satellite (LEOsat) constellations—StarLink (launched by Space Exploration holdings, LLC (SpaceX)) and OneWeb,” the report said.

“Simulations were performed of the visibility of LEOsats with 30,000 second-generation StarLink satellites below 614 km and ~48,000 OneWeb satellites at 1,200 km, in accord with the FCC filings for these projects.”

The simulations found that, at nighttime, some satellites can be seen all night long during the summer months. Scientists are collaborating with SpaceX to fix the problem. Observatories will adjust observation schedules while SpaceX will adjust satellite body orientation to reduce sunlight reflection.

Stargazing is already a more refined process than most of us think, involving three kinds of twilight and light pollution.

From Twilight to Starlight

Astronomers have differentiated when the sun is just below the horizon into three twilight phases.

“Right after sunset, we have civil twilight, and during civil twilight you can still read outside without artificial light,” said Dr. Edward M. Murphy, Associate Professor, General Faculty at the University of Virginia in Charlottesville. “Only the brightest stars and planets are visible in the sky, so we can see Venus or Jupiter or the bright star Sirius.”

Dr. Murphy said the second kind of twilight is called nautical twilight. It gets its name from the fact that during nautical twilight, several of the bright stars needed for navigation at sea become visible, but the horizon can still be seen well enough to determine those stars’ altitudes. It’s neither too early nor too late for seafarers to guide their ships.

“Finally, we reach astronomical twilight when there’s not enough light to clearly see that horizon,” he said. “At the end of astronomical twilight the Sun no longer illuminates the sky and the faintest stars and nebulae are visible in a telescope.”

Give a Hoot, Don’t Pollute

As professional and home astronomers wait patiently for twilight to end, another factor besides satellites contends with their ability to see beyond the atmosphere: light pollution.

Light pollution is the illumination of the night sky by stray light from human activities,” Dr. Murphy said. “In the light-polluted sky, the stray light from the city has lit up the distant horizon and the sky. There are no stars visible just above the city, and even high overhead there are fewer stars visible than what you would see under dark skies.”

Dr. Murphy said that light pollution is symbolic of three kinds of waste: wasted light, wasted energy, and wasted money. Anyone who’s seen a picture of the nighttime Earth from orbit will recognize clusters of lights in cities all around the world, which he said waste resources while ruining our view of the night sky.

“Light pollution can be prevented by using full cutoff light fixtures that put the light on the ground instead of the sky,” Dr. Murphy said. “An ideal observing location will have little or no stray light from bright nearby lights, such as homes and stores and street lights, and it will have clear skies and low humidity. Higher altitudes also help.”

Ideally, our interests in observing the wonders of the universe from Earth will find compromise with our endeavors in orbit.

Edited by Angela Shoemaker, Wondrium Daily

Dr. Edward M. Murphy contributed to this article. Dr. Murphy is Associate Professor, General Faculty at the University of Virginia in Charlottesville. He earned his bachelor’s degree in Astronomy from the University of Illinois, Urbana–Champaign, and his PhD in Astronomy from the University of Virginia in 1996.