On clear nights with no clouds, when you look up, you might see countless twinkling lights, some of which are moving. What are they?
No need to worry! The bright, smoothly moving object you’re seeing is an artificial satellite created by humans. There are currently fewer than 3,000 satellites orbiting the Earth, and many of these can be observed in the night sky.
Twinkling lights moving across the night sky may be artificial satellites. (Illustrative image).
These satellites are operated by private companies, national governments, and scientific agencies for various purposes. Every time you open Google Earth or Google Maps, you’ll see thousands of images of the Earth’s surface taken by these satellites! Some radio services, like Sirius XM, are also satellite-operated.
Various governments and military organizations use satellites to capture images of the Earth’s surface, whether to investigate issues related to national security or to monitor large-scale weather systems like hurricanes. Some satellites even serve as powerful astronomical tools, such as the Hubble Space Telescope, which captures stunning images of stars and other galaxies from a high enough orbit to avoid the Earth’s atmosphere.
When you look up at the night sky and see what appears to be a bright star moving quickly across the sky, what you are actually seeing is a satellite reflecting sunlight in a way that makes it visible to you.
It often moves quickly because most satellites are close enough to Earth to orbit it in less than a day (so if you’re stuck for a few hours, you might see the same satellite fly across the sky again). There’s no reason to be concerned about the satellites you see; however, many astronomers worry that launching more satellites into space (such as Elon Musk’s plan for the Starlink satellite constellation) will make it difficult for us to observe the stars and galaxies waiting to be explored.
In addition to satellites, there are several other reasons why you might see moving bright objects in the sky, including:
- Civilian airplanes: When their lights are on, they can appear as very bright objects in the sky, often as bright as or brighter than Venus.
- Weather balloons: Often floating, they can shine with the brightness of a star.
- International Space Station (ISS): It moves across the sky in an orbit that typically lies near the horizon, appearing very bright and fast.
- Meteors: They flash brightly and then disappear; these are simply shooting stars.
- Military aircraft: Artificial flying devices with lights can often cause confusion.
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