Constellations

    Cards (10)

    • The brightness of a star as seen from the Earth depends on two factors - distance and the actual brightness (or absolute brightness) of the star
    • Apparent brightness
      The star's brightness as seen from Earth
    • Comparison of stars
      • Sirius is about 27 times as powerful as the Sun
      • Rigel has the power of many thousands of suns
      • Rigel is almost 100 times farther away than Sirius
      • Sirius is about twice as bright as Rigel
    • Sirius looks very bright when viewed from Earth because it is closer to Earth
    • Astronomers consider the star's absolute brightness when comparing stars
    • Absolute brightness
      The brightness the star would have if all stars were the same standard distance from Earth
    • The Polaris is commonly known as the North Star, the brightest star in the Dipper, very close to the north celestial pole
    • Polaris stands almost motionless in the sky and appears to rotate around the north celestial pole
    • Figure 7 shows the orientation of the globe and the movement around the lamp (Sun)
    • The Polaris is used in navigation because it does not change its position in the night sky