The smallest of the asteroids wasn't alone: he had his own moon

The smallest of the asteroids wasn't alone: he had his own moon

In the spring of 2022, on 27 March, the NASA Lucy mission's scientific team discovered a satellite near the asteroid Polimel, the smallest of the Trojan targets of the probe, originally planning to observe Polimela's transit in front of the star. A total of 26 teams of professional astronomers and amateurs observed the asteroid's path. NASA was preparing to measure the location, size and shape of Polimela with unprecedented accuracy.

"A total of 14 teams reported star blinking when the asteroid was in front of it, but when we analyzed the data, it turned out that two observations were different," Mark Bewie, the head of research at the Southwest Research Institute, explained. "Two astronomers discovered an object about 200 kilometres from Polimela. Looks like it was a satellite."

Using transit data, scientists realized that the diameter of the satellite was about 5 km and rotated around Polimela, and that the diameter of the asteroid was 27 km on the widest axis. The observed distance between the two bodies was about 200 km. According to an international agreement, the satellite would not be officially named until the researchers had determined its exact orbit.

The satellite is too close to Polimel to be seen in Earth telescopes or near-Earth telescopes, without the help of a star in the background. So when it's called, it's unknown. Perhaps it won't happen before 2027. That's when Lucy will get close to the asteroid. At the time of observation, it was 770 million miles away from the Earth.