SUBJECT: THE AGE OF THE PLEIADES                             FILE: UFO2654



    
    -----------------------------------------------------------------------
    Ok...   here's the information I have been able to dig out  of  various 
    sources  of  astronomical  data  including  "The  Astronomy  Databook", 
    Gaposchkin's "Stars and Clusters" and Pasachoff's "Astronomy"  From the 
    Earth to the Universe" about the Pleiades. 
    -----------------------------------------------------------------------

    The age of the Pleiades:
    
    The  age  of star clusters and how we go about obtaining such  data  is 
    probably  best  discussed  in  Cecila  Payne-Gaposchkin's  "Stars   and 
    Clusters"  (Havard Univ.  Press).  Measuring the age of a cluster is  a 
    difficult  chore and any figures must be taken as estimates rather than 
    exact numbers.  Basically, stars of different mass,  spectral types and 
    luminosities evolve at different rates. A  blue-white O type supergiant 
    is  consuming its mass at a furious rate and only has a very short life 
    expectancy  measured  in a few millions or tens of millions  of  years. 
    Smaller,  cooler stars like the Sun (G3 type)  are much more sparing of 
    their  mass  and the sun is estimated to have a lifespan of  around  10 
    billion  years.   Red dwarf type stars may last many more  billions  of 
    years.   The  life  of a star is measured not from the  moment  of  its 
    "birth" until the time it ceases to exist, but is a measure of how long 
    that  star will exist as a "main sequence"  star - meaning how much  of 
    its  life  will be spent in a certain area on  the  Hertzsprung-Russell 
    diagram. A star like the sun may spend millions of years forming out of 
    the galactic gas,  a short time as a proto-star, 10  billion years as a 
    main  sequence star,  millions of years as a red giant...etc.  However, 
    its life is measured in terms of how long on the main sequence. 
    
    The estimates of the age of the Pleiades rest right around  100,000,000 
    years making it a very young cluster in terms of the age of the galaxy. 
    Many of even the smaller,  fainter stars have not even reached the main 
    sequence yet,  while the big,  bright hot members have already expended 
    much of their fuel and are moving off the main sequence. Such a cluster 
    is  a poor prospect for life based on the evolution of life  on  earth. 
    The  chances of life arising on any planets orbiting Pleiadian stars is 
    probably  good,  but the chances of intelligent life arising in such  a 
    short  period  - again,  based on the only model we have studied  -  is 
    slim.   It took 4 billion years for intelligent life to arise on earth, 
    and  the  chances of it happening in less than 3%  of that time is  not 
    considered likely. 
    
    The Distance to the Pleiades:
    
    The  most  accurate  means  of measuring  star  distances  is  that  of 
    measuring the absolute parallax using the 186  million mile diameter of 
    the earth's orbit as the base line.  Obviously the closer a star,   the 
    more  accurate the distance obtained.  Such parallax  measurements  are 
    considered very accurate out to about 100  light years and usable (with 
    greatly increasing error)  out to about 300 ly. Beyond 300  ly indirect 
    measurements  need be used.  The most accurate of the indirect  measure 
    techniques  involve  the use of standard "candles"  -objects  of  known 
    brightness. The most effective standard candles are the Cephid variable 
    stars.   Other methods of indirect measurement include radial  velocity 
    studies,   the  orbits of double stars and,  in many cases,   flat  out 
    guessing!  The best figures I can find for the distance of the Pleiades 
    seems to be around 410 ly. Alcyone, the brightest star in the group, is 
    listed as about 541 light years, but this apparent disparity only shows 
    the wide margins for error of any indirect measurement. Of course,  who 
    knows  what is actually being talked about when discussing the distance 
    to  a  star cluster.  Is it the mean distance to all  the  stars,   the 
    distance to the closest star or what?  Determining which stars are evey 
    part of a given cluster is not an easy job! 
    
    Astronomer's  lives  would be so much simpler if these  Pleiadians  and 
    other  "star travelers"  would stop with all their banal pronouncements 
    about "peace and living together in harmony"  (they ain't nothing new - 
    our  own philosophers and teachers have been saying the same thing  for 
    thousands of year) and start giving us basic scientific data. 
    
    The  fact  that  out  of all the  thousands  of  so-called  abductions, 
    channeled  UFO  information and the rest of the idle chatter there  has 
    never  been  a new,  VERIFIABLE piece of information must lead  one  to 
    doubt the veracity of these stories. 



**********************************************
* THE U.F.O. BBS - http://www.ufobbs.com/ufo *
**********************************************