Time: 9:00 PM
Brief
The Spring Arc, spanning from the northeast to the southeast in twilight-evening sky during this time of year, is easy to recognize if a person knows what stars to look for: those of the Big Dipper's handle, along with Arcturus and Spica. The handle stars were shown when I featured the Dipper late last month. Looking at the stars, they form a smaller arc-like shape of their own, which leads to the general direction of Arcturus: the brightest star of Boötes the Heardsman. The figure continues to Spica, with Saturn (unlabeled) near it this year as a slight distraction; don't confuse the two, as Saturn is still too far in angular separation to fall into the flow of the arc.
Detailed
Despite the common saying of "make an 'arc' to Arcturus", in remembering that the star is part of the asterism, the name of helping us remember that so easily is coincidental. Instead, Arcturus' name is derived from Greek as bear guardian. However in Arabic, besides making up the arc, Arcturus and Spica both translate in English to uplifted one(s).
Besides the hyperlinks provided for the translations, see the names and cultural significance section of the Wikipedia article for more meanings of the names.
http://en.wikipedia.org/wiki/Arcturus#cite_note-arabicdict-15
Bottom line, none of them translate to "part of the spring arc"! That is probably a good thing for a major reason: as a result of stars' proper motions, the spring arc stars used to--and will one day again--form more of a line, or a sharp curve.
What is proper motion? it is its angular change in position over time as seen from the center of mass of the solar system. Find out more here, including rate of motion:
http://csep10.phys.utk.edu/astr162/lect/motion/proper.html
The image below shows the stars of the spring arc, and the Big Dipper stick figure, which reminds us where the handle stars are in relation to the "cup".
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| *click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp. |
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