Free Map of croatia for Once every year, ixed stars other than those in close proximity to the poles, after disappearing from the night sky for a period, reappear low in the eastern sky just before the Sun rises at dawn. When the Sun is still some distance under the horizon how far depends on the entity’s brightness, location, and other factors, the object makes a brief appearance before its light is overwhelmed by the light of the sunrise. This is called a heliacal rising, and in ancient times it was considered the most important regular event in the career of a ixed star or constellation. In the case of a ixed star, the heliacal rising occurs annually on one particular day. In the case of a constellation, it obviously stretches out over a longer period, the precise duration depending on the size of the constellation and the brightness of its stars. With respect to wandering stars like planets, heliacal risings do not occur at one particular set time each year, but according to a different, more complicated schedule, depending on the planet’s orbital course. As regards comets, generally they are capable of heliacally rising in the eastern sky only whenever they are in the inner solar system whether their return is every four years or every million years and when their orbit takes them into conjunction with the Sun and then to its east side, from Earth’s perspective. Free Map of croatia 2016.