Astronomy may become a lost art.

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The night sky is in danger. This has been true for years as urban landscapes became increasingly light-polluted. But now there's a new threat, one you can't escape by driving into the countryside. It's the "mega-constellation." Companies are planning to launch tens of thousands of internet satellites into low-Earth orbit. The recent launch of just 240 SpaceX Starlink satellites has already ruined many astronomical observations.

This week the International Astronomical Union (IAU) issued a new press release describing the impact of satellite mega-constellations on astronomy. IAU astronomers simulated 25,000 satellites similar in type to the satellites of SpaceX, Amazon, and OneWeb, and here are their results:

1. The number of satellites above the horizon at any given time would be between ~1500 and a few thousand. Most will appear very close to the horizon, with only a relative few passing directly overhead.

2. When the sun is 18 degrees below the horizon--that is, when the night becomes dark--the number of illuminated satellites above the horizon would be around 1000. These numbers will decrease during the hours around midnight when many satellites fall into Earth's shadow.

3. At the moment it is difficult to predict how many of the illuminated satellites will be visible to the naked eye because of uncertainties in their reflectivity. Probably, the vast majority will be too faint to see. This depends to some degree on experiments such as those being carried out by SpaceX to reduce the reflectivity of their satellites with different coatings.

4. Even if most satellites are invisible to the naked eye, mega-constellations pose a serious problem for professional astronomy. The trails of these satellites are bright enough to saturate modern detectors on large telescopes, and wide-field scientific astronomical observations will be severely affected.

5. The Vera C. Rubin Observatory currently under construction in Chile will be particularly hard-hit. The innovative observatory will scan large swaths of the sky, looking for near-Earth asteroids, studying dark energy, and much more. According to the IAU, up to 30% of the 30-second images during twilight hours will be affected. In theory, the effects of the new satellites could be mitigated by accurately predicting their orbits and interrupting observations, when necessary, during their passage, but this is a burdensome procedure.

Source: http://www.spaceweather.com of 14 September 2020

It haven't seen the Milky Way since 1999.

The Milky Way is our galaxy. It is a spiral arm galaxy and our solar system is in the plane of the spiral arms. I live in the countryside and when I look up, I can often see it if there are no clouds overhead. It looks like a fuzzy line across the sky, a high density of stars spanning from one side of the sky to the other side.

Between the light pollution and the high rise buildings blocking the sky it was just the Moon and bright planets in Philadelphia.

I only recently saw the milky way (and was aware of what I was seeing) for the first time. During one of the power outages we had here recently. I was out on my porch that night, and because all of the lights in the area were off, I don't think I've ever seen the sky like that. It makes me wish even more that maybe cities could tone down their lighting a little bit.

Have seen it in West Virginia and in Colorado out in the mountains at night. Not recently.

South Florida never seems to get really dark. The sky always has a milky glow all night when you walk around at night in Ft.Lauderdale. Partially the urban lights.. But also it must be some combination of the low altitude and the high humidity.

on a clear day, the anaheim sky, even at 1 in the morning, has a constant deep blue glow to it. the whole city never sees darkness, it's awful.