Wednesday, June 6, 2018

Gaia, mapping the stars in the Milky Way.



-  2097 -  Gaia, mapping the stars in the Milky Way.  The Gaia spacecraft launched in 2013 has cataloged nearly 1,700,000,000 stars in our Milky Way Galaxy and beyond. Gaia has made a significant contribution to our knowledge of stars in the Milky Way.  Yet, it has only mapped 1% of the stars.  This alone is information overload.  The data set of position and motion is a 3-D map of 1,300,000,000 stars.
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-----------------------------  2097  -  Gaia, mapping the stars in the Milky Way. 
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-  We can see 2,000 to 6,000 stars in the night sky depending on how clear the atmosphere is and if you are using binoculars. What if you were using an orbiting spacecraft?  The Gaia spacecraft launched in 2013 has cataloged nearly 1,700,000,000 stars in our Milky Way Galaxy and beyond.
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-   This spacecraft is charting the entire sky.  It can measure stars’ motions and distances, properties which haven’t been inventoried on such a large scale before.  The spacecraft is in a parking orbit on the side of the Earth opposite the Sun.  This minimizes the Sun's rays interfering with the star measurement exposures. 
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-  Based on many separate observations of individual stars over 3 years, measurements can be calculated backward and forward over time.  The Gaia spacecraft's two optical telescopes and three other instruments can measure star brightness, star temperature, and star composition.  The star's color reveals the data to calculate surface temperatures.
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-  The telescopes can very accurately measure stars 30,000 lightyears away.  The resolution is equivalent to a person on Earth spotting a penny on the Moon.  The data collected allows calculations of the radial velocity of each star.  This is the speed that the star coming directly toward or directly away from the Earth.  These precise measurements of stellar motions improve our understanding of our galaxy's history and evolution.  
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-  In  addition to the stars, over 14,099 asteroids have been tracked in their orbits inside our solar system.
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-  Further and continued analysis of all this data may bring new clues about the nature and distribution of Dark Matter. Much of the Milky Way’s mass is hidden in the form of a Dark Matter halo, a shroud of matter that is invisible except for its gravitational pull. But scientists can gauge the galaxy’s unseen bulk by observing objects moving at the outskirts of the galaxy.
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-  Exoplanet updates are also on the agenda. Because NASA’s exoplanet-hunting Kepler telescope has limited ability in gauging how big stars are, the diameters of exoplanets passing in front of those stars were not well understood.   And knowing both the brightness and distance of a star helps determine its size.
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-  A disagreement over how fast the universe is expanding persists.   Gaia data reinforced the discrepancy in results between two of the methods for measuring the expansion rate.
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-  One of these techniques involves estimating the distances of exploding stars, or supernovas, and measuring how their light is stretched by the expansion of space. Gaia improved distance estimates for variable stars called Cepheids, which scientists use to estimate how far away the supernovas are has resulted in an expansion rate mismatch is now slightly worse.
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-  The Milky Way looks so passive from our vantage point.  But there is a lot of violent activity ripping up clumps of stars and stretching them into strands known as stellar streams.

-  Gaia’s measurements of stars’ motions, combined with information about their brightness and color allows astronomers to pinpoint which stars were going with the flow of the stellar stream and reveals gaps where stars seem to be missing. That could indicate the stream was disturbed in the past by a close encounter with a clump of dark matter.
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-  Some fast-moving stars are speeding through the galaxy at speeds of more than 1,000 kilometers per second.    Such high speeds must have been created by some type of enormous explosion.  In one theory, two white dwarfs swirl around one another as one steals material from the other. The thief eventually explodes and its partner is flung away at these enormous speeds.
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-  Gaia has made a significant contribution to our knowledge of stars in the Milky Way.  Yet, it has only mapped 1% of the stars.  This alone is information overload.  The data set of position and motion is a 3-D map of 1,300,000,000 stars.
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 -------------------------   Wednesday, June 6, 2018   --------------------------------
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