Sputnik 1 was launched into Earth's orbit in 1957. Since then, more than 8,300 satellites have been launched into orbit at various altitudes, with and without people aboard. Many of those satellites have long since burned up in the Earth’s atmosphere due to orbital decay. Others, mainly occupied by humans, have successfully reentered the atmosphere to either land on the ground or splashdown in the ocean.

The really cool thing is that stargazers can see many of these satellites with the naked eye. It’s hard to go more than a half-hour without seeing one zip along. Most satellites move from west to east, but some are in polar orbits. The best time to see them is in the early evening for a couple of hours after evening twilight or a couple of hours before the start of morning twilight. That’s because satellites have to reflect sunlight to be visible.

Just before morning twilight, and for a little while after evening twilight, there’s no direct sunlight available to us on the ground, but high in space, there’s still enough sunlight to bathe satellites, sending secondhand sunshine our way. During the middle of the night, the sun is entirely behind the Earth, so all satellites pass over in total darkness.

By far, the easiest satellite to spot in the Rochester sky is the International Space Station, or ISS for short. It’s as bright as a jetliner passing over. Its first component, or module, was launched in 1998, and the station was completed in 2011. It’s longer than a football field! What makes it so bright are the eight solar panels that are over a hundred feet long and nearly 40 feet wide! They bounce a lot of secondhand sunshine our way!

The ISS orbits the Earth about every 90 minutes traveling at almost 5 miles a second. It moves in a general direction from west to east across the dome of the sky. The ISS doesn’t pass over the same location each orbit. That’s because of the nature of its orbit and the fact that Earth is rotating. There can be stretches of nights when it doesn’t pass over at all. That’s why you need to have an app or a website that will let you know where and when to look. Some apps will even alert you when the ISS is expected to pass over your location on Earth.

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My favorite website for keeping up with the travels of the ISS is www.heavens-above.com. With Heavens-Above, all you have to do is configure it for your location with their massive database. Among many of its features, it’ll provide a schedule for ISS flyovers and even a sky map to track it. You can also find out when other bright satellites will be passing over. My favorite free app for tracking the ISS is ISS Tracker. Allow that app to know your location, and you’re good to go.

Depending on where it’s crossing your sky, the ISS can take up to around five minutes to pass. It resembles a super-bright star. Depending on when you’re watching it, in the early morning or early evening, it can suddenly disappear in the sky as it enters the Earth’s shadow, or pop into view coming out of the shadow in the early morning.

As much fun as it can be to observe satellites among the stars, I’m afraid that in the future, skies may become too crowded. I’m worried that it’s already beginning to happen. In particular, I’m referring to Starlink satellites launched by the Space Exploration Technologies Corporation, otherwise known as SpaceX, a private space-transportation enterprise founded in 2002 by South African native Elon Musk. He has very ambitious plans that include Earth-orbiting satellites, some with humans aboard, and also designing spacecraft that would travel back to the moon and even Mars.

SpaceX’s most ambitious project currently involves launching a possible total of 12,000 internet Starlink satellites that can provide much more available access to the internet throughout the world, even in remote areas. Already, there are 400 very reflective Starlinks in orbit, and it’s very easy to see them, sometimes in groups or lines. As it is with the International Space Station, you can keep up with all of them on the Heavens-Above website.

The big fear is that the natural beauty of the night sky could be ruined with too many satellites. Earth-based astronomical observations, both done by professionals and by amateur astronomers, are going to be interfered with significantly. I believe there must be some international regulations to keep this from happening. I can tell you as an astrophotographer, that it’s getting tougher and tougher to get time-exposure images that aren’t marred by satellite streaks.

Watching satellites is a lot of fun, but let’s not get the heavens too congested!

Possibly bright comet on the way

There are no guarantees, but as May continues, we could see a comet, maybe even with the naked eye. Comet Swan may just put on a nice show. In fact, toward the end of this week, Comet Swan may be visible very early morning pre-twilight. Look for it between about 4:15 a.m. and about 4:45 a.m. in the very low northeast sky. It’ll only be about 5 to 10 degrees above the horizon. Ten degrees is about the width of your fist held at arm’s length. You may see it with the naked eye, but you’ll probably have to use binoculars. Honestly, no one really knows just how bright it’s going to be. This melting dirty cosmic snowball will resemble a fuzzy star with a tail pointing to the upper right. Comet Swan is passing between 50 million to 55 million miles of Earth this week. Toward the end of May, Comet Swan may be visible in both the early morning and early evening sky. Stay tuned. I’ll have more on Comet Swan in next week’s Skywatch column.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications. Send questions to mikewlynch@comcast.net.

The Rochester Astronomy Club welcomes new members and puts on public star parties. Their website is rochesterskies.org.