On November 1st, the Lucy probe of NASA was able to rehearse its future observation methods with a first asteroid flyby, Dinkinesh. But the latter revealed several surprises. They discovered a world with a very original little moon. It’s a contact binary: two blocks placed against each other!
When the Lucy mission took off in 2021 to study Jupiter’s Trojan asteroids, it was expected to spend several years “gaining momentum” on a trajectory that would save it precious fuel. But in early 2023, NASA announced that with a minor modification, the probe could fly by the small asteroid Dinkinesh on November 1. A unique opportunity that immediately won all the votes.
Indeed, the technical team was able to take the opportunity to refine the automated sequences and settings for subsequent flybys, while the scientific team took advantage of rare images and data on a little-known asteroid. However, despite 60 years of space exploration, even if asteroids are the most numerous bodies in our Solar System, we know little about them, and we have only been able to fly over or study closely around twenty of them so far. . There are always surprises…
Dinkinesh is not alone!
Without being prepared in a hurry, the flight over Dinkinesh has only been planned for a few months. Which notably means that there has not been a long campaign observing this asteroid nor much dedicated “telescope time”. This explains why the Lucy probe did not come closer than 430 kilometers to Dinkinesh, even if the asteroid ultimately only measures 790m in average diameter.
A few days before the flyby, a measurement revealed unusual clarity on one side of the asteroid, but it was on November 1, a few hours after the flyby, that the teams obtained confirmation via photographs: Dinkinesh has a small moon ! The latter is initially measured at 220 meters in diameter, and it orbits very close to the main body. However, it wasn’t over yet.
From the Moon to the MoonMoon
The data from these flybys, when it is confirmed that the probe is doing well, are downloaded in chronological order. However, it may take several days to “empty Lucy’s memory” and bring everything back to Earth, and a few more days to look at everything, even before doing an in-depth study.
The scientists therefore had a nice surprise when they discovered, from a particular viewing angle, that the small moon of Dinkinesh is in fact what we call a contact binary: two small celestial bodies which landed on each other. against each other and which, in their rotation around the main asteroid, got stuck in this position (probably forever). This is not the first time that probes have observed contact binaries, but not for a small moon around an asteroid! Many Internet users have already nicknamed it “moonmoon”, even if it is neither original nor definitive.
“ It’s unusual, we can say that “, explains Hal Levison, Lucy’s chief scientist, from the Southwest Research Institute. “ I would never have expected to see a system that looks like this, especially since I don’t yet understand why the two bodies of this natural satellite are similar in size. This will really be fun for the scientific community to decipher. “. A great discovery!
Source : NASA
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