Altimate family visual dictionary(WORDS)

          STARS   Stars are bodies of hot, glowing gas that are born in Nebulae. They very enormously in size, mass, and temperature: diameters range from about 450 times smaller to over 1,000 times bigger than that of the sun; masses range from about a twentieth to over 50 solar masses; and surface temperatures range from about3,000   ˚  C to over  50,000 °  C.   The colour of a star is determined by its temperature: the hottest stars are blue and the coolest are red. The Sun, with a surface temperature of 5,500 °  C  is between these extremes and appears yellow. The energy emitted  by a shining star is usually produced by nuclear fusion in this star’s core.The brightness of a star is measured in magnitudes- the brighter the star, the lower its magnitude.   There are two types of magnitude: apparent magnitude, which is  brightness seen from  earth ,and absolute magnitude, which is the brightn...

  Stars of northen skies W hen you look at the northern sky,you look away from the densely  populated galactic centre, So the northern sky generally appears less bright than the southern sky .    Among the best known sight  in the northern sky are the constellations Ursa Major( the Great Bear) and Orion. Some ancient civilization 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 imaginary Celestial Sphere are directly above the north and South Pole 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 here, and Polaris( the pole star) lies very close to it     .The celestial equator  marks a projection of the Earth’s equator on the Sphere. The ecliptic marks the path of the sun. across the sky as the earth orbits the sun. ...

Stars of southern skies When you look at the southern sky, you look towards the galactic center, which has a huge population of stars . As a result, the Milky Way appears brighter in the southern sky than in the northern sky. The southern sky is rich in nebulae and star clusters.It contains the large and small magellanic clouds, which are 2 off the nearest Galaxy to our own.  Stars make fixed patterns in the sky called constellations.However, the constellation are only  apparent grouping of stars, since the distance to the stars in constellation may vary enormously.   The shapes of constellations may change over many thousands of years due to the relative motions of stars.The movement of the constellations across the sky due to the earth 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 the sky to be visible in different seasons.The...