If you are in Pau, Limoges, Bourges or Reims, in any case along a strip that passes through these cities between the southwest and the Ardennes, you can take part in a NASA mission by observing the sky in the night from Saturday October 22 to Sunday October 23 around 4 am. This is to find out more about an asteroid called Eurybate, which the American probe Lucy, which left Earth a year ago, will fly over in 2027.
If Lucy knows how to reach the corner of the solar system on the side of Jupiter where Eurybate is evolving, she still needs to collect a certain amount of information on this celestial object to best succeed in her mission. “The probe will fly by the asteroid and it will last only a few hours.explains Guillaume Langin, in charge of participatory science at the French Association of Astronomy (AFA). So you have a very short space of time during which the probe will want to take as much data as possible and therefore it has no room for error. She must be aiming for the asteroid, she must not pass too far from it. It must know its shape, its mass as best as possible. So we want to know all these things as much as possible in advance and that’s why in the years preceding the arrival of the probe, there were ground observation campaigns that used the technique of stellar occultations to learn as much as possible about the asteroid.”
The occultation is a kind of mini-eclipse and this is what will happen in the night from Saturday to Sunday. The phenomenon will be visible in part of the sky of Metropolis, when our asteroid will pass in front of a star in the Constellation of Gemini, the star HD 51593, thus blocking its light. “By timing how long it took for the star to disappear, we can collectively trace the contours of the asteroid and therefore deduce its shape even though it is invisible in the sky.says Guillaume Langin. We only see it through the star that it makes disappear. The second thing we can learn from stellar occultations is the trajectory of the asteroid. Until now, it is poorly known. There is an uncertainty of around 200 kilometres. There is this shadow of the asteroid which will pass over France. It could pass more or less a hundred kilometers further west or further east than predicted.”
To carry out these measurements, the French astronomy association has therefore launched a call for participation, from clubs but also from anyone with an observation tool, even the simplest, explains Marie Grand, co-organizer of the event. at the Afa: “We call on anyone, whether they have extremely seasoned astronomical equipment, or really just a small pair of binoculars, to watch since even having seen the star go out or not having seen it s ‘extinguish. This is extremely important data for researchers.”
All the information for participating in this data collection is on the association’s website: afastronomie.fr. More than 800 people have already registered.
How to help NASA learn more about the asteroid Eurybate – Olivier Emond’s explanations
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