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3I/ATLAS lowers brightness despite getting closer to Earth
The brightness of the 3I/ATLAS object has decreased quite noticeably over the past few days, by more than a third, when observed from Earth, despite the fact that the celestial body continues to rapidly approach the planet. The magnitude (the main characteristic of the brightness of celestial bodies), which was 10.1 at the beginning of the week, has increased, based on recent observations, to 10.6, which means that
the brightness of the body is now about 63% of what it was 6 days ago. Since the distance between the object and the Earth has decreased by 10 million kilometers during this time, the main reason for the decrease in brightness is probably the continued distance of the body from the Sun. Since an object classified as a comet should shine with the reflected light of the Sun, as the distance from the latter increases, the brightness of the body should also decrease. At least, this explanation looks quite natural.
However, it is possible that the decrease in brightness is also influenced by internal causes, for example, changes in the characteristics of the central body that are hidden from observation and affect its albedo. Despite the decrease in brightness, 3I/ATLAS continues to occupy a fairly high, 4th place in brightness, among almost 100 comets currently in the Earth's sky and available for observation. At the same time, comet C/2025 A6 (Lemmon), which has already been partially forgotten and dropped out of the news, continues to be in the first place, the luminosity of which has decreased by almost 10 times over the past month, but still remains at a high level. As for 3I/ATLAS, its current brightness values keep it accessible not only to scientific, but also to semi-professional instruments.