There’s a new kind of pollution showing up in our night skies and it’s getting worse.
Just a few years ago, when I saw an occasional streak of light on a photo of the night sky, my initial presumption was that it was a meteor. Now, I see streaks on many night sky photos and I assume they’re satellites in Earth orbit.
A dozen satellites photo-bombed this image of the Milky Way.
Satellites are critical to modern life. They provide communications and internet access; they collect data to forecast the weather and climate; they observe changes in the Earth’s surface; they provide navigation aid; and they help keep our country safe, to name but a few examples.
The biggest and brightest satellite in Earth orbit (excluding the Moon) is the International Space Station (ISS), the only satellite with humans aboard. Under the right conditions (i.e., the level of darkness and the optimal angle of reflection between the Sun, the ISS, and the observer), the ISS is the brightest object in the night sky, with the exception of the Moon.
The International Space Station (lower right) and an Iridium communication satellite (top center) bracket the Andromeda Galaxy (center). The Iridium satellite flared when sunlight hit its door-sized solar panel. Satellites appear as slowly moving ‘stars,’ but show as lines on this time exposure photo. The constellation Cassiopeia is at the left; the Double Cluster of Perseus is at lower left.
Satellites used to be so expensive to launch into Earth orbit that only governments had the resources to do it. However, through competition with private industry, launch costs have significantly decreased and the number of satellites in orbit is now increasing at an alarming rate. Consider the following statistics:
- There are approximately 5,000 stars in the night sky that can be seen with the naked eye. About 2,000 of these can be seen at any given time, the other 3,000 being below the horizon.
- According to n2yo.com, a site that tracks satellites, there are over 6,000 satellites in Earth orbit and the number increases every year. About half of these satellites are no longer operational (these estimates exclude classified satellites, whose numbers are unknown).
It’s worth noting that, in the last three years, SpaceX has launched over 1,000 Starlink communication satellites into Earth orbit. These Starlinks are placed into orbit in groups that look like satellite trains, slowly and silently drifting as they follow one another across the sky. They’re quite beautiful to see, but they’re becoming a real nuisance to astronomers and astrophotographers. I applaud the efforts made to make Starlink satellites less visible, but the camera still sees what the unaided eye may miss.
A ‘train’ of a dozen Starlink communication satellites cross the Double Cluster of Perseus. The satellites look like slowly drifting stars that seem to follow one another, but appear as lines on this time exposure photo. I believe that the satellites’ paths don’t overlap because the Earth is rotating beneath them. Note the two other satellites traveling in a different orbit that appear to intersect with the Starlink train toward the bottom left (their proximity is a matter of perspective).
In addition to satellites, there’s a lot of ‘space junk’ up there (e.g., spent rocket boosters). The website n2yo.com is currently tracking more than 22,000 objects in Earth orbit. That number, too, grows annually.
It’s true that some satellites are too faint to be seen and, because most satellites are in low Earth orbit and shine by reflected sunlight, they’re mostly seen for an hour or two after dark and before dawn. But, as the sheer number of satellites and pieces of space debris increase, satellites will soon be placed in higher orbits – resulting in more satellites, seen for longer periods of time. Euroconsult estimates that, within seven years, there will be 15,000 satellites in Earth orbit. That’s a ratio of three satellites to every one visible star – think about that.
The US Commerce Department has the authority to regulate American satellites. If something isn’t done to better regulate the number of satellites and make them less reflective, we’ll soon have a situation in which the night sky is in perpetual motion – observing this night sky of the near future will be like having a psychedelic LSD trip without the LSD! And I thought airplanes were the bane of astrophotographers…
However, proper satellite regulation will be difficult to achieve because the US is not the only country placing satellites in orbit — there are almost 100 countries or partnerships capable of launching satellites today.
I’m not ‘anti-satellite,’ I know they’re beneficial to humankind. But, at least paint them black or make them non-reflective, so they aren’t visible. Three satellites for every visible star will destroy our night skies. And while the number of visible stars in the sky is constant during our lifetime (ignoring the effects of light pollution), the number of satellites will eventually increase beyond the projected 15,000. We could end up with a satellite to star ratio of 5:1 or even 10:1. Where do we draw the line? Do we wait until the satellite trains become runaway trains?
One last point – ‘what goes up, must come down.’ Satellite orbits eventually decay, causing them to fall back to Earth. Gravity wins every time. Do we want 15,000 satellites raining down upon Earth over a period of years? Granted, 70% of the Earth is covered by water, so only 4,500 of the 15,000 should hit land (OK, some portion of these might completely burn up upon re-entry). Satellite re-entry is one of the reasons all satellites and space debris are continuously monitored.
Nobody’s been hurt by a falling satellite (yet). But, the odds increase as we launch more and more satellites over our heads.
I’m in no way suggesting that Save The Night Sky 285 take on satellite-related issues. Organizations like the United Nations Office For Outer Space Affairs and the US Commerce Department, as well as advocacy groups like the Union of Concerned Scientists exist to grapple with these challenges.
But, if something doesn’t change real soon, it may be time for me and others to get a new hobby!