What’s that big, bright, moving light in the sky at dusk? Chances are it’s the International Space Station (ISS). The world’s largest and brightest satellite returns for easy viewing during early evening hours this month. The ISS snuck up on me several evenings ago while I was out photographing the northern lights. Great to see it back beaming across the autumn constellations.
Just a quick summary on when to find out when it will pass over your town:
- Go to Spaceweather’s Satellite Flybys page and key in your zip code
- Pick your location in Heavens Above and you’ll get a list of predictions with local times, where to look and a nice map of each pass
- Sign up for NASA e-mail alerts
- Download a free phone app for iPhone or Android
When you know the time the ISS is expected, head out a few minutes early to make sure you’re facing in the right direction and await its arrival. The sight always seems a bit magical, since the predictions are so dead-on.
The ship’s eight huge solar panels are made of layers of thin gold Mylar plastic; they’re highly reflective and give the station a lemony color to the naked eye. If you’re fast enough to point a telescope at the moving dot of light, 60x easily reveals individual, gold-colored solar panels. Try it sometime, and you’ll be amazed at the sight.
The ISS makes a pass about every 90 minutes, so if you catch it in early twilight, you might see Act II at nightfall. Later than that and Earth’s shadow reaches so high into the sky that it blocks sunlight from reaching the station. That’s how we see it in the first place — sunlight still shines 250 miles overhead when it’s getting dark down here on Earth.
An orbit is a free-falling path an object takes — whether man-made or natural like planets and moons — around a larger body. The ISS “falls” as it goes round the Earth, the moon falls as its orbits our planet and Earth falls as it cycles around the sun every year. The reason none of them perish in catastrophic cataclysm is because all have forward momentum. If you toss a ball, it makes an arc through the air and quickly falls to the ground. If you throw it harder, it stays in the air longer before hitting the ground. But if you throw it really, really hard it, say 17,460 miles an hour (7.8 km/sec) hard, it would never fall to Earth but remain in a stable orbit circling round and round the planet.
Rocket engines provide the speed satellites need to get into orbit. As for the planets and moons, they got their speed in the infant stages of our solar system, when the original disk of dust and gas called the solar nebula spun up as it condensed and collapsed into a pancake-shaped disk from which the planets were born.
Here are a few times when the ISS will be visible across northern Minnesota and NW Wisconsin in the coming nights:
- Tonight Oct. 10 starting at 7:36 p.m. Nice, bright pass across the northern sky
- Sunday Oct. 11 at 8:18 p.m. in the northwestern sky
- Monday Oct. 12 at 7:25 p.m. across the northern sky