A bubble in space: Abell 39 marks the death of a star like the sun. Wind from the aging central star pushes into the surrounding interstellar gas, building up a dense shell that glows blue in this image. After 36 years of travel, the Voyager spacecraft is just now reaching the edge of the sun's own wind-blown bubble. WIYN/NOAO/NSF hide caption

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Gold exists, just as it really is, just as the physicist knows it to be, and that has nothing to do with us. Michal Cizek/AFP/Getty Images hide caption

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The Milky Way fills the night sky over Chile's Cerro Paranal, home to the European Southern Observatory's Very Large Telescope (VLT). Y.Beletsky/ESO hide caption

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The Milky Way dominates the sky over Chile's Atacama Desert, home to the European Southern Observatory. John Colosimo/ESO hide caption

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This illustration shows the relative sizes of the habitable-zone planets Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f and the Earth. NASA/Ames/JPL-Caltech hide caption

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Cosmic microwave background radiation (CMB) as observed by Planck. The CMB is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380,000 years old. Planck Collaboration/ESA hide caption

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Science has been working to shed light on the nature of the Universe for 400 years. Alberto Pomares/iStockphoto.com hide caption

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A computer simulation of the formation of large-scale structures in the Universe, showing a patch of 100 million light-years and the resulting coherent motions of galaxies flowing towards the highest mass concentration in the centre. The snapshot refers to an epoch about 10 billion years back in time. Klaus Dolag/VIMOS-VLT Deep Survey/ESO hide caption

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Don't panic! The end of the Universe (as we know it) isn't likely to hit us for billions of years, if it comes at all. Pictured: the Milky Way rises above the ESO's ALMA facility in Chile. José Francisco Salgado/ESO hide caption

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