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The three-dimensional structure of all cloud complexes in the solar neighbourhood is revealed, showing a narrow and coherent 2.7-kpc arrangement of dense gas, in disagreement with the Gould Belt model.

For the past 150 years, the prevailing view of the local interstellar medium has been based on a peculiarity known as the Gould Belt(1-4), an expanding ring of young stars, gas and dust, tilted about 20 degrees to the Galactic plane. However, the physical relationship between local gas clouds has remained unknown because the accuracy in distance measurements to such clouds is of the same order as, or larger than, their sizes(5-7). With the advent of large photometric surveys(8) and the astrometric survey(9), this situation has changed(10). Here we reveal the three-dimensional structure of all local cloud complexes. We find a narrow and coherent 2.7-kiloparsec arrangement of dense gas in the solar neighbourhood that contains many of the clouds thought to be associated with the Gould Belt. This finding is inconsistent with the notion that these clouds are part of a ring, bringing the Gould Belt model into question. The structure comprises the majority of nearby star-forming regions, has an aspect ratio of about 1:20 and contains about three million solar masses of gas. Remarkably, this structure appears to be undulating, and its three-dimensional shape is well described by a damped sinusoidal wave on the plane of the Milky Way with an average period of about 2 kiloparsecs and a maximum amplitude of about 160 parsecs.

When a magnetic impurity exists in a metal, conduction electrons form a spin cloud that screens the impurity spin. This basic phenomenon is called the Kondo effect(1,2). Unlike electric-charge screening, the spin-screening cloud(3-6) occurs quantum coherently, forming spin-singlet entanglement with the impurity. Although the spins interact locally around the impurity, the Kondo cloud can theoretically spread out over several micrometres. The cloud has not so far been detected, and so its physical existence-a fundamental aspect of the Kondo effect-remains controversial(7,8). Here we present experimental evidence of a Kondo cloud extending over a length of micrometres, comparable to the theoretical length xi(K). In our device, a Kondo impurity is formed in a quantum dot(2,9-11), coupling on one side to a quasi-one-dimensional channel(12) that houses a Fabry-Perot interferometer of various gate-defined lengths L exceeding one micrometre. When we sweep a voltage on the interferometer end gate-separated by L from the quantum dot-to induce Fabry-Perot oscillations in conductance we observe oscillations in the measured Kondo temperature T-K, which is a signature of the Kondo cloud at distance L. When L is less than xi(K) the T-K oscillation amplitude becomes larger as L becomes smaller, obeying a scaling function of a single parameter L/xi(K), whereas when L is greater than xi(K) the oscillation is much weaker. Our results reveal that xi(K) is the only length parameter associated with the Kondo effect, and that the cloud lies mostly within a length of xi(K). Our experimental method offers a way of detecting the spatial distribution of exotic non-Fermi liquids formed by multiple magnetic impurities or multiple screening channels(13-16) and of studying spin-correlated systems.