Heliacal rising

Heliakisch (also called " Morgenerst " and " Last Morning " ) is an umbrella term of astronomy, meaning " to the ascending sun belonging ". The term is used in connection with the culmination and the establishment and demise of celestial bodies at dawn, in particular with respect to stars, planets and the moon. The designations employed since antiquity " Morgenerst " and " morning last ," which are " heliakisch " as a synonym for find, mainly in astrology into account.

The apparent brightness of celestial bodies and the respective dusk length determine the date on which a rising in the east or a celestial body is the first time in the West under continuous celestial body for the last time seen with the naked eye at dawn. The opposite, based on the dusk term is akronychisch (also called " Abenderst " and " last night ").

Heliacal rising and setting gear and heliacal culmination

As the earth orbits the sun once a year, the sun moves from the Earth seen once a year along the ecliptic through the heavens. The stars go every day for about four minutes earlier ( / under ) than the sun. Your heliakisches appearance above the horizon can be seen with the naked eye until a few days after the passage at dawn. The star then goes earlier than the sun. The sky is not outshone by the sunlight.

Meaning in Ancient Egypt

Particularly important was the heliacal rising of Sirius in ancient Egypt as a bearer of the Nile flood. Both events took place from about 2000 BC together. Previously, the heliacal rising Sirius was too early because of the precession of the earth for the Nile flood. For the Egyptians started with the Nile flood the. For the cultivation and sowing important irrigation and supply of the Nile mud The heliacal rising Sirius also the New Year's celebration was coupled (see Sothis cycle). In Sumer, Assyria and Babylonia some stars took over with their heliacal rising important functions as a signal generator for the agricultural calendar.

A star that is approximately in opposition to the Sun goes under heliakisch, just before it rises. These events in the chronology does not signify obtained as the first visible in the eastern morning star ( heliacal rising ). The upper heliacal culmination indicates the time at dawn, at which a star in its diurnal motion the greatest height reached above the horizon or in the case of the lower culmination of the minimum height. In the ancient Egyptian astronomy the upper culminations of the Dean heliacal star was considered important (see Naos of the Decades ).

Heliacal sunrises Venus in the morning sky

The apparent relative motion between the Sun and planets is similar to the stars only in the upper planets ( but retrograde motion / loop planets when they are in opposition to the Sun ). Completely different are the conditions in the lower planets Mercury and Venus, of which the heliacal events of Venus are the more significant because of those great brightness.

The Venus ( and Mercury) will not be like the stars and the planets upper overhauled periodically by the sun in the sky apparently. She is alternately maximum for about four hours in the morning and in the evening sky, but never seen in the middle of the night because they can not come to the Sun in opposition.

Your visibility as morning star is limited by two heliacal Sunrises, one and a visible last time the first time. For the stars there is only ever one first visible rising.

Heliacal setting of the moon in the morning sky

Just as the sun the stars overhauled once a year, it will be obsolete once a month from the moon. This means that the moon rises later than the sun after it has overtaken them. Just before obtaining one sees him for the last time rising in the east at dawn ( " Morning last "). The moon has no " Morgenerst " because he never rises heliakisch but akronychisch ( " Abenderst ").

Heliakisches year

The interval between two successive Heliacal wells of a star is called the Heliacal year. The length and the beginning of such year depends on the geographic latitude and the position of the star. The length is only a tropical year, when the star has the Ecliptic latitude of 0 °.