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Brown dwarfs

18 May 2014, 00:00 UTC
Brown dwarfs Penn State University/NASA/JPL-Caltech
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¡SkyCaramba! Weekly astronomy blog for the week ending May 24, 2014
Ever since the invention of the telescope, astronomers have known there is much more to the universe than meets the naked eye. Today we understand the search for knowledge of the cosmos isn’t just about magnifying distant and dim objects until the naked eye can see them. Some of the closest and most common objects may not even emit visible light.
Stars produce heat and light through nuclear fusion. Innumerable atoms are pulled closer and closer together by each other’s gravity until there’s no distinction anymore between where one atom ends and another begins. Two hydrogen nuclei become one helium nucleus. Other hydrogen nuclei are pulled apart and become deuterium, an isotope of hydrogen. Other heavier atoms are created too. Bits of light energy called photons emerge.
It may take thousands of years for photons to escape the star’s center and millions or more to reach us. Light travel time from the sun’s surface to the earth is a little more than eight minutes. Light from the farthest known galaxy started heading our way 13.4 billion years ago.
The Hubble Space Telescope has collected quite a lot of that ...

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