from The American Heritage® Dictionary of the English Language, 5th Edition.
adjective Of or relating to the sun, especially rising and setting with the sun.
from The Century Dictionary.
In old astronomy and chronology, near the sun: applied to those risings and settings of a star which were as nearly coincident with those of the sun as they could be observed.
from the GNU version of the Collaborative International Dictionary of English.
adjective (Astron.) Emerging from the light of the sun, or passing into it; rising or setting at the same, or nearly the same, time as the sun.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
adjective Of or relating to the sun, especially rising and setting with the sun.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adjective pertaining to or near the sun; especially the first rising of a star after and last setting before its invisibility owing to its conjunction with the sun
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
[From Late Latin hēliacus, from Greek hēliakos, from hēlios, sun; see sāwel- in Indo-European roots.]
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Examples
The more precise fixing of new year's day was accomplished through observation of the time of the so-called heliacal rising of the dog-star, Sirius, which bore the Egyptian name Sothis.
In some cases the ancients took the sidereal year from the "heliacal" risings or settings of stars, that is from the interval between the time when a bright star was first seen in the morning just before the sun rose, until it was first so seen again; or last seen just after the sun set in the evening, until it was last so seen again.
These are the dog days, the days about the heliacal rising of the Dog Star, noted from ancient times as the hottest and most unwholesome period of the year, a period when malevolent influences were thought to prevail.
"... in astronomy, a term applied to the rising or setting of the stars, or more strictly speaking, to their emersion out of and immersion into the rays and superior splendor of the sun.
"A star is said to rise heliacally, when, after having been in conjunction with the sun, and on that account invisible, it comes to be at such a distance from him, as to be seen in the morning before sun-rising; the sun, by his apparent motion, receding from the star towards the east: on the contrary, the heliacal setting is when the sun approaches so near a star as to hide it with his beams, which prevent the fainter light of the star from being perceived, so that the terms apparition and occultation would be more proper than rising and setting."
—Falconer's New Universal Dictionary of the Marine (1816), 191
chained_bear commented on the word heliacal
"... in astronomy, a term applied to the rising or setting of the stars, or more strictly speaking, to their emersion out of and immersion into the rays and superior splendor of the sun.
"A star is said to rise heliacally, when, after having been in conjunction with the sun, and on that account invisible, it comes to be at such a distance from him, as to be seen in the morning before sun-rising; the sun, by his apparent motion, receding from the star towards the east: on the contrary, the heliacal setting is when the sun approaches so near a star as to hide it with his beams, which prevent the fainter light of the star from being perceived, so that the terms apparition and occultation would be more proper than rising and setting."
—Falconer's New Universal Dictionary of the Marine (1816), 191
See also acronical.
October 11, 2008