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- The Hubble Space Telescope is celebrating 25 years of space astronomy. One of its greatest discoveries in 1998 was that gravitational attraction of all the matter in the Universe was not causing cosmic expansion to slow down. Quite the opposite, Hubble’s view of the most distant supernovae explosions confirmed that cosmic expansion was accelerating.
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- This amazing discover occurred by witnessing White Dwarf stars grow to 1.4 Solar Mass and explode as a “ standard candle” supernovae, which allowed astronomers to calculate distances very accurately.
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- Somehow the vacuum of space contains energy that is more powerful than gravitational energy that decays as distance squared. If this Dark Energy represents the energy of “empty” space, which has a constant density, then the expansion will continue to accelerate forever. Distant galaxies will continue to disappear from view, farther than their light has time to reach us. The Universe will die a “ cold death” as everything separates from every thing else.
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- The rate of expansion was not well measured until Hubble used the brightness of Cepheid Variable stars. Earlier measurements put the rate of expansion at 50 kilometers per second per megaparsec to 100 km/sec/Mpc. The distance measurements in Hubble’s observations refined the Hubble Constant of Expansion to 72 km/sec/Mpc. This more accurate expansion rate allowed the calculation for the age of the Universe back to the Big Bang to be 13,800,000,000 years.
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- Hubble Deep Field observations at a single point in the sky for a very long time exposure witnessed thousands of galaxies in an area of the sky no bigger than looking through a soda straw. Given the Universe is the same in every location and in every direction meant that the Observable Universe contains many hundred billion galaxies.
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- Hubble’s observations have concluded that essentially every galaxy that has a bulge of stars at its center hosts a super massive Blackhole. The mass of these Galactic Blackholes ranges from a few tens of thousand times the Sun’s mass to a few billion Solar Mass. Hubble could measure the mass by the velocity dispersion of the stars orbiting the central Blackhole.
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- Hubble used gravitational lensing to map out Dark Matter surrounding a foreground galaxy cluster. These 3-dimensional maps have allowed astronomers to create web-like structures in space that acts as scaffolding for normal matter and the formation of galaxies and galaxy clusters.
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- Hubble working with the Chandra X-ray Observatory have mapped out a clear separation of Dark Matter and hot ordinary matter present in colliding galaxy clusters.
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- Since 1991 nearly 2,000 planets have been discovered in other solar systems. Hubble has witnessed some transiting planets passing in front of their star. A small fraction of the star light passes through the planet’s atmosphere. The spectrum analysis of this light has detected the elements sodium, hydrogen, carbon, oxygen and water vapor in the planet’s atmosphere.
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- Hubble Deep Field images have explored the galaxy populations back to when the Universe was only 500 million years old. This is in the “ Reionization” era of cosmic evolution.
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- Reionization was when the Universe was “ dark”. After the Big Bang the Universe was filled with a hot plasma, or free protons and free electrons. 380,000 years later the protons and electrons began combining into neutral hydrogen. When plasma ions (charged particles) were neutralized the cosmos became transparent and “ first light” escaped.
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- The “ first light” today is seen as the Cosmic Microwave Background radiation as the expanding Universe has stretched the light waves out into microwaves. At that point in the evolution stars had not yet formed from the fusion of hydrogen. That took another 200 million years later. The first stars produced mostly ultraviolet radiation that further bombarded neutralized hydrogen atoms back into charged particles, protons and free electrons. It took an billion more years for this Reionization to be completed.
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- Hubble is waiting to be replaced by the James Webb Space Telescope to explore the faintest objects that existed at the end of Reionization. We are literally studying the birth of the Universe. Stay tuned , there is much more to learn.
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