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The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| The very high-luminosity infrared galaxies - Are they very young?
It is proposed that most of the very high-luminosity IRAS galaxies,those which emit greater than or equal to 10 to the 12th solarluminosities nearly all in the far infrared out to 100 microns, are veryyoung systems with ages less than or equal to 10 to the 9th years. Theluminosity comes largely from stars with masses near 100 solar masseswhich evolve rapidly, ejecting much of their mass as elements heavierthan hydrogen. The gas ejected condenses into dust in circumstellarshells. The prototype star in the Galaxy which shows all of theseattributes is Eta Car. It is shown that total masses of order 10 to the7th-10 to the 8th solar masses condensed into such stars can produce theobserved luminosities, and that 10-100 generations of such stars willproduce enough dust (about 10 to the 8th solar masses) to explain theobserved infrared luminosities. If this hypothesis is correct thecomposition of gas and dust may well be highly anomalous, and thereshould be no old stars with ages about 10 to the 10th years present.Initial star formation is probably triggered by interactions with closecompanion galaxies.
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