: relating to or near the sun - used especially of the last setting of a star before and its first rising after invisibility due to conjunction with the sun's rising and setting
The heliacal rising of Pleiades marked the beginning of summer in the old Julian calendar, which was introduced by Julius Caesar.
"Nowadays, if you wish to watch the heliacal rising of Sirius, you've got to wait until August. This is because Earth wobbles on its axis ... and over several millennia, the positions of celestial objects shift slightly." - From an article by Dennis Mammana in Newsday (New York), July 14, 2012
Did You Know?
The word "heliacal" rose in the mid-16th century. Its source is the Greek word "hēlios," meaning "sun." Helios is also the Sun god of ancient Greece. "Heliacal" often suggests a relationship between a star and the sun as they appear to the human eye in the sky, as in our example sentences. It's also used in reference to the ancient Egyptian year, which began on the date when Sirius (or the Dog Star) first appeared on the eastern horizon at sunrise. English speakers have referred to this year as the heliacal year or the Sothic year. ("Sothic" comes from "Sōthōs," the Greek word for Sirius.)
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