[HN Gopher] The New Story of the Milky Way's Surprisingly Turbul...
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       The New Story of the Milky Way's Surprisingly Turbulent Past
        
       Author : pseudolus
       Score  : 22 points
       Date   : 2024-01-28 12:28 UTC (2 days ago)
        
 (HTM) web link (www.scientificamerican.com)
 (TXT) w3m dump (www.scientificamerican.com)
        
       | morphle wrote:
       | https://archive.ph/DOK5W
        
       | chasil wrote:
       | "Astronomers are making the first exact maps of the Milky Way:
       | locations of stars in three dimensions..."
       | 
       | I thought that "standard candles" were required to estimate the
       | distance to any region of space?
       | 
       | How can the distance to arbitrary stars be determined without
       | these markers?
        
         | thatswrong0 wrote:
         | Gaia is orbiting around the L2 Lagrange point. As it traverses
         | its orbit, the stars will appear to wiggle (relative to their
         | previous recorded position) because of the stellar parallax
         | effect. This (along with precisely knowing Gaia's orbit)
         | enables scientists to accurately measure the distance to the
         | star - if it wiggles more, it's closer. If it wiggles less,
         | it's further away.
         | 
         | There is a limit to this method of measurement, based on the
         | accuracy of the telescope. For Gaia:
         | 
         | > The European Space Agency's Gaia mission is expected to
         | measure parallax angles to an accuracy of 10 microarcseconds
         | for all moderately bright stars, thus mapping nearby stars (and
         | potentially planets) up to a distance of tens of thousands of
         | light-years from Earth.
         | 
         | The Milky Way is about 100,000 light-years wide. So it is able
         | to accurately measure the distance for a _lot_ of stars around
         | us in our galaxy.
         | 
         | This video probably explains it better:
         | https://www.youtube.com/watch?v=Jdy09y0A4t0
        
           | vikingerik wrote:
           | To be clear (and the video isn't), the parallax is observed
           | and calculated mostly from the diameter of Earth's orbit,
           | with observations made six months apart. Gaia's L2 orbit is a
           | much smaller factor, on the order of 1M km compared to
           | Earth's orbital diameter of 300M km.
        
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       (page generated 2024-01-30 23:01 UTC)