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The Goat Star

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    The Goat Star: A Strange Light in the Northeast By Joe Rao SPACE.com s Night Sky Columnist, SPACE.com Recently I received an interesting inquiry from Professor
    Message 1 of 1 , Sep 19, 2003
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      The Goat Star: A Strange Light in the Northeast

      By Joe Rao
      SPACE.com's Night Sky Columnist, SPACE.com

      Recently I received an interesting inquiry from Professor Rob
      Eisenson, Assistant Professor in the Dept. of Physics, Astronomy, and
      Meteorology at Western Connecticut State University.

      "In recent SPACE.com columns you have been advising people to look
      for Mars low in the southeast sky after nightfall," Eisenson
      writes. "Yet, I have also been seeing another unusually bright star-
      like object, but low in the north-northeast sky soon after it gets
      fully dark. It isnt so much that it is bright, it is just that I dont
      recall ever seeing such a bright star located so far to the north. It
      also sometimes seems to twinkle with the same kind of yellowish-
      orange light that Mars shows now. Can you identify what I am seeing?"

      What Professor Eisenson was looking at is indeed a brilliant star
      with a distinct yellowish hue. In fact, its the sixth brightest in
      the sky (magnitude 0.08) and as seen from mid-northern latitudes,
      ranks number four behind Sirius, Arcturus and Vega.

      It is Capella, in the constellation of Auriga, the Charioteer.

      Auriga is one of those star patterns whose exact origin is a hopeless
      mix of antique conceptions. The Greek and Roman legends made Auriga a
      famed trainer of horses and the inventor of the four-horse chariot.
      But the most ancient legends also had Auriga as a goatherd and a
      patron of shepherds. The brilliant golden-yellow Capella was known as
      the "Goat Star," with a nearby triangle of fainter stars representing
      her kids.

      The confusion in concepts is reflected in the ancient allegorical
      pictures and star names. Auriga is usually represented holding a whip
      in one hand in deference to the Charioteer story, but in his other
      arm he is holding a she-goat (Capella) and her three kids.

      In his classic guidebook, "The Stars, A New Way to See Them"
      (Houghton Mifflin Company, Boston), Hans A. Rey (1898-1977) drew
      Auriga looking like a man with a tough expression, a jutting chin and
      a pug nose, " . . . as befits the driver of a war cart."

      Capella measures 16 times as large in diameter as our Sun, 174 times
      as luminous, and is located 42 light-years away. It is part of a
      multiple star system, interestingly containing at least four stellar
      components.

      As was noticed by Professor Eisenson, Capella appears to rise well to
      the north of due east. In fact, it is the nearest to the North Pole
      of the sky of all the first-magnitude stars, and across much of the
      48-contiguous United States it is visible at some hour of the night
      throughout the year.

      From western Connecticut, for example, Capella is below the horizon
      for only about 3 hours out of a 24-hour day. Lying 46 degrees north
      of the celestial equator, Capella can pass directly overhead for
      anyone living at that latitude north of the terrestrial Equator (say,
      Houlton, Maine or Geneva, Switzerland). And for anyone at points
      north of latitude 44 degrees (for example, Minneapolis, Minnesota or
      Bologna, Italy), Capella will appear to graze the northern horizon,
      but will not go below it.

      Interestingly, the brilliant blue-white star Vega is only a trifle
      brighter and lies almost diametrically opposite in the sky from
      Capella and at about 39-degrees from the celestial equator, affords a
      similar rising reference for northern sky watchers in the early
      spring sky.

      Rise times

      In the table below, we have prepared the rise times for Capella for
      three dates this week (Sept. 19, 22 and 25) as seen from 10 different
      latitudes, each separated by 2-degree increments. Also provided for
      each latitude is the azimuth the direction on the horizon where
      Capella will first appear. As already noted, from latitude 44 degrees
      and all points north, Capella is always above the horizon.

      All times are given in civil or local daylight time (LDT), which
      differs from ordinary clock time by many minutes at most locations.
      Most civil time zones worldwide have been standardized on particular
      longitudes at increments of 15. As an example, across Europe, 0 (the
      Greenwich Meridian); 15 east; 30 east, etc. Across North America,
      there is 60 west (Atlantic Time), 75 west (Eastern Time), 90 west
      (Central Time), etc. If your longitude is very close to one of the
      standard meridians, luck is with you and your correction is zero.

      To get local standard time, add four minutes to the times listed for
      each degree of longitude that you are west of your time zone
      meridian. Or subtract four minutes for each degree you are east of it.

      Your clinched fist, held at arms length will measure roughly 10
      degrees. So 20 degrees would measure roughly "two fists" when making
      an estimate of azimuth.

      EXAMPLE: From Durham, North Carolina, on September 22, when and where
      will Capella appear to rise? Durham is located near latitude 36 north
      and longitude 79 west. Looking at the column under September 22, we
      see a rise time of 8:51 p.m. for latitude 36. But since Durham is
      located 4 west of the Standard meridian, we must add 16 minutes to
      8:51 p.m. So Capella will actually rise at 9:07 p.m. From the
      latitude of Durham, Capella will appear to rise 27 degrees east of
      due north, or less than "three fists" to the east (right) of due
      north.

      For other dates and latitudes, you can interpolate.

      ...
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