As a night-sky enthusiast, I enjoy spending time just looking up to the cosmos and marveling at all the celestial objects. There they are, suspended in the air, moving ever so slowly across the night sky. However, every once in a while, I catch a faint glimpse of something tiny and dim moving slightly faster against the background of stars.
Satellites! There are hundreds of them up there orbiting out planet. Over 900, in fact. Most of them are small and inconspicuous. But there are many bigger ones that can catch your eye if look in the right place at the right time!
The biggest and brightest earth-orbiting object (other than the Moon), is the International Space Station (ISS). Its solar arrays span more than 240 feet from tip to tip, nearly as long as a football field. And when those puppies catch the sunlight just right, the reflection can be super bright. Brighter than even the planet Venus. Only the Moon and the Sun shine brighter than ISS at its peak!
The ISS shines because of the Sun's light reflecting off the solar arrays and the rest of the giant space station's body. But how does the Sun light it up when it is dark out? Good question! You see, even though the Sun has set and it is dark outside, the ISS orbits the Earth at an extremely high altitude, 230 miles above the Earth to be exact. So, even though the Sun has set, the space station is high enough to catch some of the rays streaming beyond the horizon. Well, that is until the ISS finally orbits around into Earth's shadow, which doesn't take too long. The ISS orbits Earth at roughly 4.8 miles per second (287 miles per minute or 17,250 miles per hour), completing nearly 16 loops around our planet everyday.
A couple good places to go to find out when and where to spot the ISS and other bright satellites are www.Heavens-Above.com and www.spaceweather.com/flybys/. These sites will list bright satellite passes over your location for the next several days. Put in your location and look for a date and time that will have a nice, bright, visible ISS fly-over. Go outside a couple minutes before the designated start time and scan the sky in the general direction of the beginning of the fly-over as described at the website. For the ISS, look for a bright, slow-moving object. Depending on the angle of the fly-over, the ISS could be as bright or brighter than the planet Venus. It will appear to move in a relatively straight line a little bit slower than a high-flying airplane. An ISS fly-over will generally last anywhere from four to six minutes before it finally dips into the Earth's shadow. Once you spot it, be sure to give a nice big wave to the astronauts aboard!
Since OneDarkSky is based in Elgin, IL, I will start posting some of the upcoming brighter ISS fly-overs that can be seen from this area. Look for the updates and forecasts in the Satellites forum.