1. CLASSIFYING STARS

2. GOALS Understand how stars are grouped Understand the different ways a star can be named Explain how astronomers classify objects by apparent brightness

3. CONSTELLATIONS Semi-rectangular regions of the sky with definite boundaries

4. CONSTELLATIONS 88 official constellations. Cover the entire sky Every star is part of one constellation

5. CONSTELLATIONS

6. NAMES OF STARS Common Names Many bright stars have ancient names Usually of Arabic, Greek or Latin origin Examples Betelgeuse Achernar

7. NAMES OF STARS The Bayer System (1603) Greek + possessive form of the Letterconstellation Greek letters assigned in order of brightness – Alpha (α) = brightest star – Beta (β) = second brightest

8. NAMES OF STARS Flamsteed System (1712) Number +possessive form of the constellation Number stars from west to east

9. NAMES OF STARS Example Common NameDeneb ConstellationCygnus Bayer NameAlpha Cygni Flamsteed Name50 Cygni

10. BRIGHTNESS OF STARS The Magnitude Scale – brightness scale Stars divided into six brightness groups – The brightest = first-magnitude stars – The faintest = sixth-magnitude stars

11. BRIGHTNESS OF STARS Apparent Visual Magnitude (m V ) A measure of the brightness as seen by human eyes on Earth. Does not take into account star’s distance from Earth

12. BRIGHTNESS OF STARS Apparent Visual Magnitude (m V ) Non-linear scale 1 magnitude = 2.5 times brighter Backwards Smaller magnitude = brighter

13. BRIGHTNESS OF STARS Differences in the scales 1.Star magnitudes can have decimal values. 2.The brightest stars have negative magnitudes 3.Telescopes allow one to view dimmer stars. The magnitude system was extended beyond the 6 th magnitude

14. GOALS - SUMMARIZE Understand how stars are grouped Understand the different ways a star can be named Explain how astronomers classify objects by apparent brightness

15. CONCEPT CHECK 1.If Jupiter is reported to be in the constellation of Taurus the Bull, does Jupiter need to be within the outline of the bull’s body? Why or why not? 2.Which constellation can Alpha Centauri be found in? 3.The star Zubenelgenubi has a apparent magnitude of 2.75, while Sulafat has an apparent magnitude of 3.25. Which star appears brighter?