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A circumpolar constellation is a constellation (group of stars) that never sets below the horizon, as viewed from a location on Earth. As viewed from the North Pole , all fully visible constellations north of the celestial equator are circumpolar, and likewise for constellations south of the celestial equator as viewed from the South Pole .
Some constellations have only seasonal appearances, which help mark the passage of time. For example, Ullakut ( Orion ) and Sakiattiak ( Taurus ) are only visible in the winter. Throughout winter, many stars within Tukturjuit ( Big Dipper ) were used as hour hands to keep track of time during the night or as calendar stars to determine the date.
Different cultures and countries invented their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity.
The term circumpolar is somewhat localised as between the Tropic of Cancer and the Equator, the Southern polar constellations have a brief spell of annual visibility (thus "heliacal" rising and "cosmic" setting) and the same applies as to the other polar constellations in respect of the reverse tropic.
Ursa Major, also known as the Great Bear, is a constellation in the northern sky, whose associated mythology likely dates back into prehistory.Its Latin name means "greater (or larger) bear", referring to and contrasting it with nearby Ursa Minor, the lesser bear. [1]
Seasonal reckoning in the military of any country or region tends to be very fluid and based mainly on short to medium term weather conditions that are independent of the calendar. For navies, the presence of accessible ports and bases can allow naval operations during certain (variable) seasons of the year.
In some locations, early cultures assembled massive artifacts that may have had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year.
For identical reasons, the apparent position of the Sun relative to the backdrop of the stars at some seasonally fixed time slowly regresses a full 360° through all twelve traditional constellations of the zodiac, at the rate of about 50.3 seconds of arc per year, or 1 degree every 71.6 years.