In the Alps, Noema scrutinizes the cold Universe


Noema, you deserve it. Acronym for Northern Extended Millimeter Array, Noema is the most powerful observatory in the northern hemisphere in the field of millimeter radio astronomy, where the wavelengths observed are of the order of a millimeter. And to benefit from the purest possible sky, the one where the turbulence of the atmosphere is least felt, this installation is perched at an altitude of more than 2,500 meters, in the alpine massif of Dévoluy. More precisely on this summit table that is the plateau of Bure.

To get there, you must first go to the SuperDévoluy ski resort, then, aboard a 4 × 4, go up the slopes along the chairlift pylons, covered and immobile in this season. Finally, when the path ends, the serious things begin. Where the vehicles no longer pass, only the strength of the legs remains, in a mineral environment, where the last rickety trees give up clinging to the side of the mountain. Amid layers of clear scree rises a rocky path whose slope, at times, flirts with painful 40% even as the scarcity of oxygen begins to be felt. Yes, Noema, you deserve it.

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But, when the last scree is passed, when out of breath we finally set foot on the plateau, on this sea of ​​pebbles, where only a few yellowed tufts of grass bent by the winds and a few patches of moss float, we are rewarded. . Higher than the clouds, facing the jagged bar of the Ecrins whose fangs nibble at the bottom of the azure, you touch the sky by raising your hand. And, in the hollow of an undulation of the plateau, a herd of immense parabolas point towards the firmament. Here is Noema, built by the Institute of Millimeter Radio Astronomy (IRAM) and whose twelfth and last antenna entered service at the beginning of the year, but which will not be officially inaugurated until September 30.

For the time being, only ten of the twelve parabolas are in action on the set, the last two being in a giant hangar for summer maintenance, in order to be ready for the winter which, with its extreme dry cold freezing the atmosphere, is the favorite season for radio astronomers. With a diameter of 15 meters, each antenna weighs more than 120 tons and the 176 aluminum panels that line its reflective surface are adjusted by actuators to obtain a perfect shape, with a precision of 35 micrometers, i.e. the thickness of the antenna. a human hair.

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