Status: 02.10.2023, 04:45 a.m.
By: Tanja Banner
In the sky above the Subaru telescope in Hawaii, a mysterious blue spiral can be seen. © National Astronomical Observatory Japan
There are many glowing objects in the night sky. But how do you find out if you've observed a star, a planet, a satellite, or something else entirely?
Munich – When the temperatures are mild in spring and summer, people like to spend more time outdoors and look at the starry sky at night. There are many objects there that shine brightly and are especially noticeable if you don't look at the sky often. Whether it's a bright, seemingly immobile light, a "star" moving rapidly across the sky, or some other phenomenon that catches your attention, most celestial observations can be explained relatively easily.
The most important information to find out what you have seen in the sky is the direction of the compass and the time of observation. If you don't have a compass handy, you can use the sun to roughly determine which direction you're looking. For example, use the well-known mnemonic phrase "The sun rises in the east, it rises high in the south. In the west it will perish, in the north it will never be seen." The direction alone can make some things easier to explain. In the spring of 2023, for example, the planet Venus will be very brightly visible in the west in the evening. Therefore, if you spot a very bright "star" in the west in the evening, it is most likely the "evening star" Venus.
"Bright light" in the sky does not move: a star or planet
If you see a "bright light" in the sky that does not move even for a long time, it is most likely a star or a planet. To distinguish them, take a closer look: stars twinkle, planets do not. The twinkle of the stars is caused by the turbulent Earth's atmosphere, which light must pass through to reach the human eye. Although the light from planets also penetrates through the Earth's atmosphere, the sparkle is usually not noticeable because planets are significantly brighter.
If you're still unsure whether you've seen a star or a planet, there are other options. For example, use a digital star map such as the free "Stellarium" app (also available for smartphones) to find out what you have discovered in the sky. After installing the app, you can point your smartphone at the celestial body to find out what it is. To distinguish a star from a planet, it also helps to observe the celestial body for several nights. Planets move across the starry sky over time, moving from one constellation to the next. That's why they used to be called "walking stars".
"Bright light" moves quickly across the night sky: a satellite or airplane
If you see a "bright light" moving rapidly across the night sky, there are also several possibilities of what you might have observed. It could be a satellite or an airplane, for example. The distinction is relatively simple: planes flash, satellites do not. If the object is flashing in the sky or has green or red lights, it is an airplane. They can recognize satellites by the fact that they do not blink, but move across the sky as more or less bright points of light and suddenly disappear again.
With some experience, you can distinguish different types of satellites. For example, SpaceX's "Starlink" satellites usually occur in larger groups – one satellite is followed by several others. The International Space Station (ISS), on the other hand, which can occasionally be seen in the night sky, remains alone and shines much brighter than the "Starlink" satellites. You can track the trajectories of different satellites with apps like "Stellarium" or "Heavens Above". In addition to the direction of observation, you also need the exact time at which you made your observation.
Shortly after launch, the "Starlink" satellites are still very close together and can hardly be missed in the sky. Many observers describe the sight as a "string of lights" or a "trail of light". (archive image) © imago images/Belga
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Unusual sightings: "Starlink" satellites confuse in the sky
In addition to these everyday sky observations, there are also more unusual sightings where people even call UFO reporting centers. The UFO Reporting Office of the Central Research Network of Extraordinary Celestial Phenomena (CENAP) provides information about these phenomena, although balloons or drones are often behind the observations. Most often, however, the "Starlink" satellites confuse people looking at the sky.
This is not surprising: they are not only to be seen as individual satellites flying at a distance one after the other. Shortly after take-off, they are very close to each other, creating an almost ghostly trail of light in the sky. Many observers refer to the "Starlink" satellites as a "string of lights" in the sky after launch.
Rocket launches can also look strange in the sky
Also, different phases of rocket launches can look strange in the sky. For example, a spiral can occur when a rocket stage releases its remaining fuel. You can also occasionally see rocket parts burning up or the separation of a rocket stage in the sky. On the other hand, shooting stars, meteors and fireballs are of natural origin. In this case, a more or less large stone from space penetrates the earth's atmosphere and burns up. Information about other sightings of fireballs can be found in a special database, where you can also report your own sighting.
This article, written by the editors, used machine support. The article was carefully reviewed by editor Tanja Banner before publication.