Nearly five kilometers above sea level on Chile’s Chajnantor plateau, one of the driest places on Earth, the Atacama Large Millimeter/Submillimeter Array (ALMA), shown in figure 1, has a prime view of the cosmos, unhindered by light pollution, radio interference, or atmospheric scattering. So it’s little wonder that when the telescope’s state-of-the-art antennas turned their eyes toward the nascent star Elias 2-27, they picked out a detail that previous radio telescopes had missed: The star’s circumstellar disk—an unresolved blob in previous images—harbors a pair of extensive spiral arms.1 

The observation, reported by Laura Pérez (Max Planck Institute for Radio Astronomy) and an international team of collaborators, bolsters one of the harder-to-confirm predictions of astrophysical hydrodynamics: Under certain conditions, the spinning disk of gas and dust that surrounds a gestating star will contract under the weight of its own gravity into spiral density waves. If Elias 2-27’s spiral structures...

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