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Radio astronomers: sun travels at 135 miles per sec.

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  • Frits Westra
    http://www.nandotimes.com/noframes/story/0,2107,55450-88668-629794-0,=00.htmlRadio astronomers say sun travels 135 miles per second around Milky Way
    Message 1 of 1 , Jun 5, 1999
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      http://www.nandotimes.com/noframes/story/0,2107,55450-88668-629794-0,=00.html

      Radio astronomers say sun travels 135 miles per second around Milky
      Way

      Copyright � 1999 Nando Media
      Copyright � 1999 Associated Press

      By PAUL RECER

      CHICAGO (June 2, 1999 11:04 a.m. EDT http://www.nandotimes.com) - It
      may seem like the sun is just creeping through the heavens, but a new
      technique for measuring cosmic motion has found that Sol is clipping
      along at an eye-popping 135 miles per second in its orbit of the Milky
      Way.

      Astronomers using a radio telescope system to make the most precise
      measurement ever of the solar system orbit found that it takes the sun
      and its family of planets 226 million years to circle the center of
      its home galaxy.

      That means that the last time the sun was at this point in its orbit
      of the Milky Way, dinosaurs ruled the world and human beings were not
      yet on the scene.

      The new measurement is the most precise value ever determined for one
      of the fundamental motions of the Earth and its sun, said James Moran
      of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
      He spoke Tuesday at the national meeting of the American Astronomical
      Society.

      "Our new figure of 226 million years is accurate to within 6 percent,"
      Mark Reid, a Harvard-Smithsonian astronomer and leader of the team
      that made the measurements, said in a statement.

      The sun is one of about 100 billion stars in the Milky Way, one of
      billions of ordinary galaxies in the universe. The Milky Way is a
      spiral galaxy, with curving arms of stars pinwheeling out from a
      center. The solar system is about half way out on one of these arms
      and is about 26,000 light years away from the center. A light year is
      about 6 trillion miles.

      Reid and his team made the measurement using the Very Long Baseline
      Array, a system of 10 large radio-telescope antennae placed 5,000
      miles across the United States, from the U.S. Virgin Islands in the
      east, to Hawaii in the west. Working together as a single unit, the
      antennae are able to measure motions in the distant universe at an
      unprecedented accuracy.

      The accuracy is such that the VLBA can look at a bit of sky that has
      an apparent size one-ten thousandth the diameter of a human hair held
      at arms length.

      For their solar system measurement, the astronomers focused on
      Sagittarius A*, a star discovered two decades ago to be at the center
      of the Milky Way. Over a 10-day period, they measured the apparent
      shift in position of the star against the background of stars far
      beyond.

      The apparent motion of Sagittarius A* is very, very small, just
      one-600,000th of what could be detected with the human eye, the
      astronomers said.

      Reid said the measurement adds supports the idea that at the center of
      the Milky Way is a supermassive black hole.

      "This ... strengthens the idea that this object, much smaller than our
      own solar system, contains a black hole about 2.6 million times more
      massive than the sun," Reid said in a statement.

      Moran said the new measurement of the solar system orbit adds new
      accuracy to a fundamental fact of the universe: Everything is moving
      constantly.

      The Earth rotates on its axis at about 1,100 miles an hour, a motion
      that creates day and night. The Earth orbits the sun at about 67,000
      miles an hour, a motion that takes one year. The sun circles the Milky
      Way at a speed of about 486,000 miles per hour. And the Milky Way,
      along with every other galaxy, is moving away from each other, as the
      universe expands at a constantly accelerating rate.
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