Gaia: A Galactic Revolution

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    Gaia: A Galactic Revolution  https://www.bbc.co.uk/programmes/b0b2xw15

    For past three and a half years, ESA's Gaia Space telescope has been mapping the heavens in unprecedented detail. At the end of April 2018 it released precise data on over 1.3 billion stars in the Milky Way showing how they move over time and their distance from Earth.
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    “Like the drift of the continents or the erosion of great mountain ranges on Earth, the motion of the stars across the sky is almost imperceptibly small over the paltry span of a human lifetime. But in this quite astonishing video made with data from the European Space Agency’s (ESA’s) Gaia spacecraft, which compresses 5 million years of star motion into a few minutes, you can see more than 2 million stars move across the sky like grains of pollen floating in a breeze. It is mesmerizing (and unexpectedly calming).

    This video is the culmination of nearly 300 years of discovery. Until the dawn of the Enlightenment, most astronomers believed, as Aristotle declared nearly two thousand years earlier, that the stars were fixed and unchanging, if for no other reason than they appeared so. But in the 18th century, Edmund Halley, during one of his star mapping expeditions to St. Helena in the south Atlantic, noticed the position of the bright star Arcturus differed noticeably from that noted in the 2nd century B.C. by the ancient Greek astronomer Hipparchus. He called this apparent motion the “mutability of the fixed stars”. We now call it proper motion, the apparent motion of a star across the celestial sphere.”

    https://www.youtube.com/watch?v=nUnKDPk60gU Best to watch this video full screen.

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