Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2025 December 30
A star filled sky shows bands of green and purple sky glow. In
the foreground is a grassy field with clouds on the horizon. Most 
remarkably, a series of short streaks appear like a comet's
tail up from the horizon toward the upper left. 
Please see the explanation for more detailed information.

An Artificial Comet
Image Credit & Copyright: Wang Chao

Explanation: Yes, but can your comet tail do this? No, and what you are seeing is not the tail of a comet. The picture features a cleverly overlayed time-lapse sequence of a group of satellites orbiting Earth together in June. Specifically, these are Starlink communications satellites in low Earth orbit reflecting back sunlight before sunrise to Inner Mongolia, China. Although the satellites appear to the human eye as points, the 20-second-long camera exposures caused them to appear as short streaks. Currently there are over 9000 Starlinks in orbit, with more being launched nearly every week. Other satellite constellations are also being planned.

Explore the Universe: Random APOD Generator
Tomorrow's picture: celestial waterfall


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