Thursday, August 23, 2018

STARS OF NORTHERN SKIES & SOUTHERN SKIES.


STARS OF NORTHERN SKIES   


            When you look at the northern sky, you look away from the densely populated Galactic centre, so the northern sky generally appears less brighter than the southern sky. Among the best-known sights in the northern sky are constellations Ursa Major (the Grear Bear) and Orion.

Some ancient civilizations believed that the stars were fixed to a celestial sphere surrounding the Earth , and modern maps of the sky are based on a similar idea. 
The North and South Poles of the North and South Poles of the Earth, at the points where the Earth's axis of rotation intersects the sphere. 

The celestial North Pole is at the centre of the map shown below, and Polaris (the Pole Star) lies very close to it. The celestial equator marks a projections of the Earth's equator on the sphere. 
The ecliptic marks the path of the Sun across the sky as the Earth orbit the Sun . The moon and planets move against the background of the stars because the stars are much more distant , the nearest star outside the Solar System (Proxima Centauri) is more than 50,000 times further away than the planet Jupiter.



STARS OF NORTHERN SKIES
THE PLOUGH, PARTS OF URSA MAJOR (THE GREAT BEAR)

STARS OF NORTHERN SKIES
PEGASUS AND ANDROMEDA

STARS OF NORTHERN SKIES
ORION

STARS OF NORTHERN SKIES
VISIBLE STARS IN THE NORTHERN SKY

STARS OF SOUTHERN SKIES   

                     When you look at the southern sky, you look towards the Galactic centre, which has a huge population of stars. As a result , THE MILKY WAY appears brighter in the southern sky is rich in nebulae and star clusters . It contains the large and small Magellanic Clouds, which are two of the nearest galaxies to our own.

Stars make fixed patterns in the sky called constellations. However, the constellations are only apparent groupings of stars, since the distances to the stars in a constellation may vary enormously.
The shapes of constellations may change over many thousands of year due to the relative motions across the sky is due to the Earth's motion in space.

The daily rotation of the earth causes the constellations to move across the sky from east to west, and the orbit of the Earth around the sun causes different areas of sky to be visible in diffirent seasons.
The visibility of areas of sky also depends on the location of the observer. For instance, stars near the celestial equator may be seen from either hemisphere at some thime during the year , whereas stars close to the celestical poles (the celestical South Pole is at the centure of the map shown below) can never be seen from the opposite hemisphere.

STARS OF SOUTHERN SKIES
VISIBLE STARS IN THE SOUTHERN SKY

STARS OF SOUTHERN SKIES
CENTAURUS & CRUX AND CANIS MAJOR
STARS OF SOUTHERN SKIES
SAGITTARIUS (THE ARCHER)
STARS OF SOUTHERN SKIES
HYDRUS (THE WATER SNAKE) AND MENSA (THE TABLE)

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