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News Eagle - Hawley, PA
  • Looking Up: How far are the stars?

  • How big is the Universe? One could also ask such philosophical questions as how small are we? Given the minuscule atoms and even smaller particles making up those atoms that make up matter all around, it seems we are somewhere in the middle as we either look out with our telescope or look down with our microscope.
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  • How big is the Universe? One could also ask such philosophical questions as how small are we? Given the minuscule atoms and even smaller particles making up those atoms that make up matter all around, it seems we are somewhere in the middle as we either look out with our telescope or look down with our microscope.
    This almost vanishing small planet we call home was considered large until our age of quick transportation and global communication. Earth, however, seems like a tiny speck of dust compared to the vastness of the Milky Way Galaxy where we abide. Earth, with its 6 billion human passengers continually spins as it circles the Sun with the rest of the family of local planets. The Solar System in turn hurtles around in a lopsided loop around the Galaxy, moving at about 150 miles a second. Don’t get sea sick! Despite that rate, the Sun and the planets takes about 250 million years to complete one circuit of the galactic hub.
    How can we tell how vast the Universe is? There are several methods. Lacking a tape measure long enough, we have a very accurate method known as parallax, which detects how a foreground star or something in the Solar System has shifted, in respect to much farther background stars. To do this we need to know the length of the base line where the different observations are made.
    If you have two observers only hundreds of miles apart and photograph the Moon at the same instant, one can readily tell the shift of the Moon’s placement next to any stars in the background. Employing trigonometry, we can then measure the distance to the Moon.
    To find the distance of a star, astronomers use the diameter of the Earth’s orbit as a base line- from where Earth is one date to the opposite point on the other side of the Sun, a half year later. This is approximately 186 million miles. Measuring the varying angles of observation to the star in question, we can detect the parallax shift for stars as far as about 400 light years.
    That’s how far light travels in 400 years, which is about 2,346,000,000,000,000 miles. Four hundred light years, however, is still in the Sun’s neighborhood. The entire Milky Way Galaxy is around 120,000 light years across and about 12,000 light years thick at the center, tapering to spiral arms about 2,000 light years thick. Our galaxy has an estimated 200 to 400 billion stars. How do we know their distance?
    No matter how far, the stars and planets are as close as your backyard the next clear evening.
    New Moon is on June 27.
    Keep looking up!
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