classifying stars - Piscataway High School

CLASSIFYING STARS GOALS •  Understand how stars are grouped •  Understand the different ways a star can be named •  Explain how astronomers classify objects by apparent brightness CONSTELLATIONS •  Semi-‐rectangular regions of the sky with definite boundaries CONSTELLATIONS •  88 official constellaKons. •  Cover the enKre sky •  Every star is part of one constellaKon CONSTELLATIONS NAMES OF STARS Common Names •  Many bright stars have ancient names •  Usually of Arabic, Greek or LaKn origin Examples •  Betelgeuse •  Achernar NAMES OF STARS The Bayer System (1603) Greek + possessive form of the LeXer constellaKon •  Greek leXers assigned in order of brightness –  Alpha (α) = brightest star –  Beta (β) = second brightest NAMES OF STARS Flamsteed System (1712) Number + possessive form of the constellaKon •  Number stars from west to east NAMES OF STARS Example •  Common Name •  ConstellaKon •  Bayer Name •  Flamsteed Name Deneb Cygnus Alpha Cygni 50 Cygni BRIGHTNESS OF STARS The Magnitude Scale – brightness scale •  Stars divided into six brightness groups –  The brightest = first-‐magnitude stars –  The faintest = sixth-‐magnitude stars BRIGHTNESS OF STARS Apparent Visual Magnitude (mV) •  A measure of the brightness as seen by human eyes on Earth. •  Does not take into account star’s distance from Earth BRIGHTNESS OF STARS Apparent Visual Magnitude (mV) •  Non-‐linear scale •  1 magnitude = 2.5 Kmes brighter •  Backwards •  Smaller magnitude = brighter BRIGHTNESS OF STARS Differences in the scales 1.  Star magnitudes can have decimal values. 2.  The brightest stars have negaKve magnitudes 3.  Telescopes allow one to view dimmer stars. The magnitude system was extended beyond the 6th magnitude GOALS -‐ SUMMARIZE •  Understand how stars are grouped •  Understand the different ways a star can be named •  Explain how astronomers classify objects by apparent brightness CONCEPT CHECK 1.  If Jupiter is reported to be in the constellaKon of Taurus the Bull, does Jupiter need to be within the outline of the bull’s body? Why or why not? 2.  Which constellaKon 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?

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