2023-11-03 22:08:05
“You are wonderful” is the translation of “Dinkinesh”. The word is Amharic, the lingua franca of Ethiopia, and also refers to the early human woman “Lucy,” whose famous skeletal fossils were found in that country. The American space probe “Lucy” was named after her and flew past its first target on November 1st: an astroid that was only discovered in 1999 and which orbits the sun at a distance of just over twice the distance of the Earth and which until it was photographed in Lucy’s travel program in January 2023 had the provisional label “1999 VD57” but is now called “152830 Dinkinesh”.
Now the space fragment has done an unexpected honor to this name. In the first images that the probe sent to the control center after the antenna alignment with Earth was restored, not one asteroid can be seen – but two. Dinikesh has a moon.
Fluctuations in brightness
Although that’s obviously not entirely true. According to previous data, the larger part of “152830 Dinikesh” with a diameter of around 790 meters and its companion, which is around 220 meters in size, rotate around a common center of gravity that lies outside the volume of the larger partner. In such a case, planetary scientists prefer to speak of a double asteroid instead of an asteroid with a moon. The two celestial bodies are only between three and four kilometers apart. The partial images in the animation below were taken by Lucy’s navigation camera at 13 second intervals.
Even though the dual nature of Lucy’s first target ultimately surprised the researchers, when they saw the images, such a thing had definitely been considered before the encounter, according to a NASA press release. In the weeks before the flyby, the probe was able to observe fluctuations in Dinkinesh’s brightness, which suggested the possibility of a double system. But because Lucy was flying toward the asteroid duo at a speed of more than 10,000 miles per hour, her cameras were unable to distinguish the two partners until the minutes of the actual flyby, about 270 miles away.
The Dinkinesh system – the smaller partner does not yet have its own name – is nothing completely unusual or even new. In the past, double asteroids have been discovered from time to time during observations of asteroids with telescopes from Earth. Scientists estimate that a good 15 percent of all asteroids are double or even multiple systems. And if the size ratio of Dinkinesh’s two components seems somehow familiar to the viewer, it is because the ratio of their volumes, at around 46:1, is close to that of the Earth and Moon pair (50:1).
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There are also asteroid pairs with much larger volume ratios, but also those in which both partners are almost the same size. This is the case with Patroclus and Menoetius, the former has a diameter of around 113 kilometers and the latter around 104 kilometers. Incidentally, Lucy will also visit this system – it orbits far out along Jupiter’s orbit – in March 2033. At the very end of her official mission.
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