With its antennas in place, the NOEMA observatory promises new observations

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With its antennas in place, the NOEMA observatory promises new observations

Part of the NOEMA Observatory's twelve 15-meter diameter antennas.

With its twelve antennas in place, the most powerful millimeter radio telescope in the Northern Hemisphere, perched on a high plateau in the French Alps, promises discoveries ranging from the composition of nearby comets to the origins of life in the Universe.

Any visitor to the NOEMA observatory (for Northern extended millimeter array) completes on foot and at an altitude of 2550 meters the journey which leads to an alignment of domes sparkling in the sun, in a mineral setting dotted with rare clumps of rock. #x27;grass and still virgin snow.

The installation has already allowed considerable advances in astronomy, such as the vision of the hearts of galaxies, explains, in the little icy wind which sweeps the plateau of Bure (Hautes-Alpes), Frédéric Geth, astronomer and deputy director of the #x27;Institut de radioastronomie millimètre (IRAM).

Created in 1979 on the initiative of the German Max Planck Institute and the French National Center for Scientific Research (CNRS), IRAM was later joined by the Spanish National Geographic Institute (IGN). Its flagship has long been the large Pico Veleta radio telescope in Spain, with its 30-meter-diameter cupola.

Size matters in millimeter radio astronomy to pick up extremely weak electromagnetic wave signals. A galaxy, for example, emits these waves in frequencies ranging from X-rays, the most energetic, through visible light, to radio waves, the lowest in energy (millimeters and centimeters).

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Radio waves are those of the cold Universe, i.e. everything but the stars, and this is the realm of NOEMA.

Bure's aluminum domes are only 15 meters in diameter, but their resolving power lies on the one hand in their number, which has increased from six in 2014 to twelve this year, and, on the other hand, in their configuration.

Mobile, despite their 120 tons each, they are arranged on two tracks forming a T.

This is the trick of the observation technique by interferometry: it consists in pointing at exactly the same moment the same object in space with several cupolas, which form a virtual cupola as large as the distance separating the furthest from each other.

He then returns to the correlator, a modest-looking supercomputer housed in a small room of the observatory, to combine the received signals by skilful calculations to restore a single image.

Winter sees the device of domes stretch out in its wide configuration, with a maximum distance of 1.7 kilometers. This is the main moment of observation, when the atmosphere is ideal, with dry, cold and stable air, explains Frédéric Geth.

The facility revolves around an imposing maintenance hall which houses NOEMA's small control room. A cable car, reserved for equipment, transports the equipment necessary for the maintenance of the domes, and the supply of the permanently inhabited living base.

The base is accessed by a hallway sheltering from bad weather and snow that will soon cover the set. The domes are monitored like milk on the fire, with a heating system so that neither ice nor dew disturbs their observations.

In the control room, André Rambaud, an operator, controls their pointing in front of a bank of screens. Let's go for the observation of eight galaxies, which are ten or twelve billion light-years away and which the cupolas will follow for five hours, he says with a smile.

IRAM astronomer Edwige Chapillon chooses the order of observation of projects that have been accepted – up to nearly 500 per year – depending on their nature and the weather.

NOEMA's science isn't the sexiest, as its astronomers agree. It is difficult to compete with the general public with the breathtaking images of the new James Webb space telescope, for example.

But this formidable time machine, as Edwige Chapillon, specialist in extragalactic observations, brings decisive breakthroughs to the understanding of the Universe.

IRAM observatories have discovered almost half of the known interstellar molecules, the bricks of life in the Universe, notes the astronomer. And it is thanks to NOEMA that astrophysicists have precisely determined the temperature of the young Universe, less than a billion years after the big bang.

The IRAM network is part of the EHT (Event Horizon Telescope) initiative bringing together the main radio telescopes in the world (including ALMA in the Southern Hemisphere), which produced the first images of black holes.

NOEMA joined the network in 2021.

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