Comet 3I/ATLAS was discovered on July 1, 2025. As soon as there were enough data to calcuate an orbit, it became clear that this object was from outside our solar system. This was only the third visitor from interstellar space discovered so far, so astronomers were excited to get as much information about it as possible.
Although it was still very small and faint, on July 23 I tried to capture some images by aiming at its predicted location in the sky. This animation loop of five images shows the comet's movement over a period of 20 minutes (the images were taken 5 minutes apart). The comet appears as a dim point to the lower left of center in this image, moving from left to right. It was about magnitude 17 at the time, too dim to be seen visually with even a very large backyard scope.
These images were cropped and enlarged from the original exposures. The width of this field is about 8 arcminutes.
As it got closer to the Sun in late 2025, the comet's brightness increased to about magnitude 12 and it could be viewed in typical amateur telescopes.
July 23, 2025