Why a Satellite Disappears in the Night Sky
Wonder why a satellite disappears mid-pass? Learn how Earth’s shadow changes what you see, how to tell satellites from aircraft and when to watch again.
You are watching a bright point move steadily among the stars. A few seconds later, it fades and disappears even though the sky is clear. The satellite has probably entered Earth’s shadow. This is a normal part of many visible passes.
Why can we see a satellite?
Most satellites do not produce the light we see from the ground. Like the Moon, they reflect sunlight. A satellite can therefore remain bright when the ground is already dark, especially shortly after sunset or before sunrise.
What happens in Earth’s shadow?
Earth blocks sunlight and casts a shadow into space. When a satellite crosses that shadow, it no longer reflects enough light towards you and seems to switch off. The fade may be gradual or quick, depending on the satellite’s path and altitude. NASA explains this effect in its guide to observing satellites.
Can a satellite suddenly become brighter?
Yes. Its brightness changes with its orientation and the way its surfaces reflect sunlight. A brief reflection can create a noticeable flare. A change in brightness does not necessarily mean the object has changed speed or direction.
How is it different from an aircraft?
A satellite normally moves silently and steadily without coloured lights. An aircraft often has flashing red, green or white lights and may be audible. A satellite can disappear in the middle of a clear sky when it enters Earth’s shadow.
How can you predict a visible pass?
Your location, the time, the elevation of the pass and sunlight all matter. AstroAlert calculates noteworthy events for your position and focuses on objects passing high in the sky. Check the app before going outside, arrive a few minutes early and choose a place with an open view.
Want to recognize the object you saw? Read our guide to seeing a satellite with the naked eye and our comparison of ISS and Starlink passes.
Discover AstroAlert to see what is passing above you and receive an alert at the right time.
