Show Me a Dawn, or "Heliacal," Rising
What Jack Eddy found at Bighorn were alignments to three stars during their
heliacal risings.
Heliacal risings occur after a star has
been behind the Sun for a season and it is just returning to visibility.
There is one morning, just before dawn, when the star suddenly reappears after its absence.
On that day it "blinks" on for a moment just before the sunrise and just before it is
then obliterated by the Sun's presence.
That one special morning is called the star's heliacal rising.
Each day that passes after the heliacal rising, the star will appear to rise earlier and
remain in the sky longer (that is, not blink)
before its soft glow is obliterated by the rising sun.
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| Computer generated heliacal risings (Quick Time required) |
Aldebaran
Shown rising 2 days before the Summer Solstice
| Rigel
Shown rising 28 days after the Summer Solstice
| Sirius
Shown rising 28 days after Rigel's Dawn rising,
and signifying the end of summer and time to leave the mountain
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Not all stars have heliacal risings
because some stars remain above the horizon all the time. Only certain stars rise and flash into existence in the
predawn glow of the horizon.
Because these helical risings were so
specific, just one day, they were used by many different ancient civilizations to mark specific events such as the
drought season and planting time. It is not surprising that the Plains Indians would use heliacal risings to signal
the coming and going of the solstice.
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