This artist's impression shows the surroundings of a supermassive black hole, typical of that found at the heart of many galaxies. The black hole itself is surrounded by a brilliant accretion disc of very hot, infalling material and, further out, a dusty torus. There are also often high-speed jets of material ejected at the black hole's poles that can extend huge distances into space. L. Calçada/ESO hide caption

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L. Calçada/ESO

This artist's view shows an exoplanet orbiting the young star Beta Pictoris. The exoplanet has an eight-hour day — and a much faster rotation than any planet in the solar system. L. Calçada/N. Risinger/ESO hide caption

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L. Calçada/N. Risinger/ESO

Taking Stock In The Search For Aliens

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Cajal summarizes many of the properties of astrocytes in this drawing of the hippocampus of a man three hours after death. Courtesy Instituto Cajal del Consjo Superior de Investigaciones Científicas, Madrid, © 2017 CSIC hide caption

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Courtesy Instituto Cajal del Consjo Superior de Investigaciones Científicas, Madrid, © 2017 CSIC

This simulated 3-D perspective view of Chasma Boreale, a canyon that reaches 570 kilometers (350 miles) into the north polar cap on Mars, was created from image data taken by NASA's Mars Odyssey spacecraft. NASA/JPL/Arizona State University, R. Luk hide caption

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NASA/JPL/Arizona State University, R. Luk