Talk:Heliacal rising

Pronunciation
Could someone who knows add the proper pronunciation for heliacal?--agr (talk) 20:21, 2 July 2010 (UTC)


 * If you're curious about the pronunciation you can get an audio reading from Tom Bowyer's amazing site howjsay. I agree it would be great to add the proper IPA for this term.Robert Hiller (talk) 05:38, 31 January 2011 (UTC)

Ancient Egypt and the Nile flood
The most famous heliacal rising would probably be the prediction of the Nile flood by the ancient Egyptians. This might be added to the article if true.Robert Hiller (talk) 05:38, 31 January 2011 (UTC)

Edit request
There is an error on this page staging the the "new moon" is something like Heliacal Rising. It is not the same. Heliacal rising happens after the Sun "passes" a star as the Sun "moves" easterly direction through the year. Star's are first engulfed by the light of the Sun, then as the Sun leaves them "behind" they appear to rise before the Sun in the morning. The moon's apparent motion in relation to the Earth and the Sun makes it so that the Sun will never be seen to "pass" the moon - the moon always "passes" the Sun. The "new moon" is therefore not actually not Heliacal, but more similar to Acronychal rising. From New moon "In non-astronomical contexts, new moon refers to the first visible crescent of the Moon, after conjunction with the Sun." italics mine.
 * Red information icon with gradient background.svg Not done: please provide reliable sources that support the change you want to be made. Mlpearc  ( open channel ) 17:26, 26 October 2015 (UTC)

This "Edit request" is correct. The "Crescent New Moon" (Hebrew: Chodesh, Arabic: Hilal) is not "like" the Heliacal Rising. The Heliacal Rising of a star always occurs close to the eastern horizon before sunrise, while the Crescent New Moon always can be observed close the western horizon after sunset. This is correcly described on https://en.wikipedia.org/wiki/New_moon under "Lunar calendars", cited here: "In non-astronomical contexts, new moon refers to the first visible crescent of the Moon, after conjunction with the Sun. This takes place over the western horizon in a brief period between sunset and moonset, and therefore the precise time and even the date of the appearance of the new moon by this definition will be influenced by the geographical location of the observer. The astronomical new moon, sometimes known as the dark moon to avoid confusion, occurs by definition at the moment of conjunction in ecliptical longitude with the Sun, when the Moon is invisible from the Earth. This moment is unique and does not depend on location, and in certain circumstances it coincides with a solar eclipse.". The reason for this is also correctly given by the author of this "Edit request": the Moon has the shortest apparent orbital period (one lunar month, about 29,5 days), the sun a much longer apparent orbital period (one year, about 365,24 days), and the "fixed" stars are just that, "fixed", at least as seen from the Earth during "shorter" periods of time (some hundreds of years -- of course they do have proper motion, but it is so small that it can be neglected here). /Erik Ljungstrand (Sweden). — Preceding unsigned comment added by 130.241.158.201 (talk) 14:45, 19 September 2016 (UTC)

Semi-protected edit request on 21 February 2017
Towards the end of the article on Heliacal Rising, it is stated: "The Moon's heliacal rising (a.k.a. the new moon) often determines the start of a month in a lunar calendar..."

The New Moon is the first sighting of the sliver crescent just after sunset. The New Moon does NOT appear before sunrise, which is the definition of Heliacal Rising.

More correct:

"The Moon's heliacal rising, near the end of the lunar month, earned her the title 'Lucifera,' or 'Light-Bringer' as mentioned by Cicero (De Natura Deorum, II, xxvii. Trans. H. Rackham, Harvard University Press, 1933, p. 191)."

Best,

George Latura 24.151.45.147 (talk) 01:09, 21 February 2017 (UTC)

Not done: please provide reliable sources that support the change you want to be made. Morphdog (t - c) 17:30, 26 February 2017 (UTC)

There is no "heliacal rising" of the Crescent New Moon
It is not true that the Moon has a "heliacal rising (a.k.a. the new moon)". Only a star, or a planet which (apparently) moves slower than the Sun over the sky, can have a heliacal rising, which is defined as "[T]he heliacal rising: the first visible, though brief, appearance of a star on the eastern horizon before sunrise [emphasis mine]. On the previous morning, sunlight made the star invisible." (see e.g. https://sizes.com/time/risesetstar.htm or Bickerman, E. J. 1968: Chronology of the Ancient World, p. 143). The Crescent New Moon, au contraire, is always observed on the western horizon after sunset (see e.g. https://en.wikipedia.org/wiki/New_moon or Bickerman, E. J. 1968: Chronology of the Ancient World, p. 16). The anonymous "Edit request" of 2015 (?) was correct, as George Latura of 2017 was, and I cannot understand why "Mlpearc" and "Morphdog" did not check the astronomical definitions themselves, instead of insisting in letting entirely wrong information about the "heliacal rising" of the Moon persist on Wikipedia. /Erik Ljungstrand (Sweden).

I have made the change myself, and erased the wrong sentence about the "identity" of the "heliacal rising" and the Crescent New Moon. /Erik Ljungstrand (Sweden). — Preceding unsigned comment added by 130.241.158.201 (talk) 09:15, 8 April 2018 (UTC)

"Heliacal"
A statement early in the lede should mention that "heliacal" means it is related to the sun and that the word has nothing to do with the words "helix" nor "helical". Run into so many people where they are baffled by the term because they think the word is related to "helix"/"helical" instead of "heliakos" (ἡλιακός) (or related word "helios"). "Heliacal" is almost non-existent in the minds of most people, but "helical" and "helix" are fairly well known, so the confusion isn't too surprising; we should probably nip that confusion fairly early in the lede. — al-Shimoni  (talk) 06:59, 7 October 2019 (UTC)

Other cultures
In New Zealand, the Māori festival of Matariki occurs with the heliacal rising of the Pleiades. Should this be linked?

Visible for more than half the year
Objects are visible for much more than half a year. Gemini, for example has its Heliacal rising in July and setting in June, being visible at night for the intervening nearly 11 months. This can be confirmed by pretty much any planetarium software or star chart generator. A zodiacal constellation (which is on the ecliptic) is only in the same part of the sky as the sun for about a month (1/12 of a year, thus 12 zodiacal constellations) the rest of the time it either comes up before the sun or sets after it, thus being visible for at least part of the night. The exact length of time a star or constellation is not visible at night obviously depends on both the observer's latitude and the star's declination. Sirius, being somewhat south of the ecliptic, rises just before the Sun in early August (Heliacal rising) and then is in the sky every night until late May when it no longer sets after the Sun (Heliacal setting). 2601:940:C000:96BC:EC6B:D94:1614:4EE1 (talk) 03:51, 10 August 2022 (UTC)