can you tell me more about the sphere mentioned above?
The Northern Hemisphere is the half of Earth that is north of the Equator and the Southern Hemisphere is the half of Earth that is south of the Equator.
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the Equator. 
what is rigel? It s a blue supergiant star in the constellation of Orion. where did the word originate from? Latin. upon observing, how can you differentiate it from others? It is typically the seventh-brightest star in the celestial sphere, it is visible on winter evenings in the Northern Hemisphere and on summer evenings in the Southern Hemisphere. In the Southern Hemisphere, it is the first bright star of Orion visible as the constellation rises.
wiki:25692183
Northern Hemisphere [SEP] Introduction
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole. Owing to the Earth's axial tilt, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year.