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The heliacal rising of a star (or other body such as the moon, a planet or a constellation[1]) occurs when it first becomes visible above the eastern horizon at dawn, after a period when it was hidden below the horizon or when it was just above the horizon but hidden by the brightness of the sun. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates [1] Each day after the heliacal rising, the star will appear to rise slightly earlier and remain in the sky longer before it is hidden by the sun (the sun appears to drift eastward relative to the stars along a path called the ecliptic). The ecliptic is the apparent path that the Sun traces out in the sky during the year Eventually the star will no longer be visible in the sky at dawn because it has already set below the western horizon. This is called the heliacal setting. A star will reappear in the eastern sky at dawn approximately one year after its previous heliacal rising. Because the heliacal rising depends on the observation of the object, its exact timing can be dependent on weather conditions. [2]

Not all stars have heliacal risings: some may (depending on the latitude of observation on the earth) remain permanently above the horizon, making them always visible in the sky at dawn, before they are hidden by the brightness of the sun. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001

Constellations containing stars that rise and set were incorporated into early calendars or zodiacs. The word Calendar consist of two words 1 Cal ( in Pashto means Year in Hindi and Persian is Sal- also means Year Zodiac denotes an annual cycle of twelve stations along the Ecliptic, the apparent path of the sun across the heavens through the Constellations that divide the ecliptic The ancient Egyptians based their calendar on the heliacal rising of Sirius and devised a method of telling the time at night based on the heliacal risings of 36 stars called decan stars (one for each 10° segment of the 360° circle of the zodiac/calendar). Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now Sirius is the brightest star in the night sky with a visual Apparent magnitude of &minus1 The Decans (also bakiu (Egyptian dekanoi (Greek drekkana (Sanskrit) are a way of grouping Stars or reckoning time that originated in The Sumerians, the Babylonians, and the ancient Greeks also used the heliacal risings of various stars for the timing of agricultural activities. Sumer ( Sumerian: sux-Latn [[Ki (earth ki]]-[[EN (cuneiform en]]-'''ĝir15''', Akkadian: Šumeru; possibly Biblical Shinar Babylonia was an Amorite state in lower Mesopotamia (modern southern Iraq) with Babylon as its capital The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c To the Māori of New Zealand, the Pleiades are called Matariki and their heliacal rising signifies the beginning of the new year (around June). This article discusses the Māori people of New Zealand For their language see Māori language, and for other meanings see Māori (disambiguation. New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island The Pleiades (ˈpliːədiːz or /ˈplaɪədiːz/ also known as M 45, the '''Seven Sisters''', Seven Stars, SED, Matariki In the Māori language Matariki is the name of the Pleiades Star cluster, which was important for Agriculture in establishing the correct time

The corresponding rising of a celestial body above the eastern horizon at nightfall, for example, that of the full moon, is called its acronychal rising.

References

  1. ^ John Britton's & Christopher Walker's chapter 'Astronomy and Astrology in Mesopotamia' in "Astronomy before the telescope", 1969, British Museum Press, Pg 48
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