Constellations What Where When International Astronomical Union IAU

Constellations What – Where - When

International Astronomical Union ► IAU - governing body for astronomy ► Collection of astronomers from multiple countries ► Must be Ph. D level or greater currently doing either research or education in astronomy ► Currently 8, 858 members ► Established 1919 with the charge of naming of celestial objects and features found on those objects

What are they? ►A particular region of the sky with a group of stars that may or may not be part of a dominate pattern in the region. Devised by the IAU ► The IAU employed Eugene Delporte in 1930 to come up with a “map” § He drew lines or boundaries along RA and declination lines § Lines and drawings were based on 1875 data. § The wobbling of the earth has created curves in the lines. § The wobbling is called precession, North star will not and has not always been at our north celestial point

What types of objects/ things? ► Currently, 14 men and women, 9 birds, two insects, 19 land animals, 10 water creatures, two centaurs, one head of hair, a serpent, a dragon, a flying horse, a river and 29 inanimate objects are represented in the night sky. ► Most of these are meant to be representations only. Some match their name, but it’s not a requirement.

Where did they come from? ► Earliest written record is from 270 BC. ► Additional research determined that the recorded constellations were from an older civilization living along the 36° latitude. We reason this because… § They were lacking the southern hemisphere, primarily south pole constellations § Ecliptic and circumpolar constellations were well diagrammed ► Probably Babylonians or Sumerians then Egyptians or Cretans

First recognized The ecliptic pattern (path of the sun) was well established ► The constellations of the ecliptic were noted because of the similarity in paths. ► § These were used as a crude calendar and rough seasonal marker. § They were later deemed the zodiacal signs

Symbols and drawings used for zodiac

Why name them? ► Early civilizations had little to no written language among the general population § History and cultural traditions were passed down orally § Many of the stories reinforced social standards by illustrating the results of nonadherance ► Navigation used the positions of the stars, sun and moon to determine the resultant position on earth § The sun and moon were most often used § They used their respective angles from the horizon to determine their position in conjunction with pre-made charts § Stars were used at night. So consistent references could be made, they were named.

Other sources ► Many cultures have had their own names and stories for the same stars world wide. ► Because the European scientific community made the formal rules (IAU), other cultural names were either discarded or transformed towards their standards

Ptolemy ► First published listing – Almagest ► Included the sum of Greek astronomy and 48 constellations with descriptions § This also included 1, 022 named stars with brightness listed § His 48 are basis for our current 88 constellations § Major contributors to filling in gaps came from sea merchants or explorers

Were there changes? ► Many many astronomers have attempted to fill in the gaps by honoring someone/thing in the sky ► They never stuck ► Examples include a listing of animals such as the toad, leach and spider! ► Political honors, kings, were generally ignored by individuals from other countries

Star Relationships ► The stars in constellations generally have no connection to the other stars ► Their appearance of being close, is just an illusion created from our perspective here on earth ► There are exceptions, but to few to mention

Constellation relationships ► As mentioned earlier, civilizations used stories to pass down history ► Stories were used to tie multiple constellations together to aid in remembering both placement and names ► Read the next few slides to see how it works –

Chapter 1 ► Queen Cassiopeia is imprisoned by her husband. She is forced to sit upside down in the sky forever.

Chapter 2 ► Princess Andromeda is chained to a rock by her mother, Cassiopeia, after angering her. The intention is that the sea monster Cetus will come devour her.

Chapter 3 ► Perseus, after finding his love is destined to be killed, captures the famed steed of Pegasus. That sprang from the ground after beheading Medusa.

Chapter 4 ► Pegasus of course, is the winged horse that is ridden by Perseus so that he may turn Cetus into stone. This of course saves andromeda from a horrible death

Here’s how they look in the sky