While Tahoe does not have the darkest skies, they are much darker than most places. And if your neighbors don't leave lights on at night, you can see a spectacular night sky. Many times we have seen amazing sights from our deck.
Recently, we had friends visiting, and we all noticed a dramatic light traveling through the evening sky.
We guessed it was the International Space Station. We'd seen the ISS several times in the past. Each time it was really bright.
Our friend pulled out her iPhone, on which she has the SkyViewLite app, which is free. She pointed her phone at the sky, and it immediately identified the ISS. (It also identifies all other major objects in the sky.)
Why is the ISS so bright? Because it is huge. With its solar panels, it is bigger than a football field. The perfect viewing time is soon after sunset or before sunrise, when our area and sky are dark but the ISS is still in sunlight because it is 250 miles above us. The sunlit space station is the second brightest object in the night sky after the moon.
What does the station look like from Earth?
It appears to my eyes as a brilliant white dot, quite large and with a hint of its rectangular shape. With binoculars, it appears more rectangular.
Like all other satellites in low-Earth orbit, the ISS traverses the sky in a few minutes. It is traveling, after all, at 17,000 miles per hour, or roughly ten times the speed of a very fast bullet! It goes all the way around the Earth every 90 minutes.
It's easy to see by using one of the websites that tell when and where to look for the ISS. NASA has a good one:
https://spotthestation.nasa.gov/
You can search on the closest city to you. When a blue tear drop shows on the map near your location, click on it. Look for the words "View Sighting Opportunities," and click on that. You'll get a list of times the ISS is visible in your area.
Pay attention to the maximum height angle the ISS will be. If it's only 20 degrees above the horizon, you may not see it because of nearby trees and buildings. But if it's going to be 60 or more degrees, you'll have a great view.
The space station has a continuous crew of 7 astronauts, and they live in various tube-shaped, pressured compartments vaguely reminiscent of an airliner. The total amount of indoor space is about the same as a 747, about 6000 square feet.
You may wonder, why do astronauts in orbit experience weightlessness? Because, like the station itself, they are actually in a kind of permanent free fall. But instead of falling down to Earth, they are going so fast they fall "past" the Earth.
When you come to the Bay Area, consider attending a guided tour of the Mt. Hamilton Lick Observatory property to learn about each of the domes. Inside the Shane Dome we saw and learned about the reflecting telescope. Outside, after watching the sunset, we went into the old library to hear a lecture about James Lick. Then when the sky was dark enough, we each had a turn to view celestial objects through the James Lick Telescope in the South Dome. We saw the Izar binary star system (20 ly away), the Messier 5 globular cluster (25 kly away), and the Spindle Galaxy (50 mly away).
ReplyDeletehttps://www.lickobservatory.org/events/public-evening-tours/