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28

Ceres, Pallas, Juno and Vesta were all discovered between 1801 and 1807. After that, astronomers looked in vain for 38 years until the 5th, Astraea was spotted on December 8, 1845 by German amateur astronomer Karl L. Hencke by accident. He stumbled on Astraea while looking for Vesta one night. So, what took so long to discover Astrea? There is a paper1 which ...


11

15 years. Hubble was designed with an anticipated 15-year lifetime based on the expected integrity of the main mirror. It was believed that over HST’s 15-year life the space environment in low Earth orbit would cause sufficient degradation of the mirror that the telescope’s light-gathering capabilities would be severely damaged by cosmic rays and orbital ...


5

It's surprisingly hard to research this, partly because the name "H-alpha" only became common towards the end of the 19th Century, and partly because (I get the impression) a lot of mid- and late-19th Century spectroscopy ignored the red end of the spectrum, perhaps because the equipment was less sensitive there. Thus, you can find a fair amount of ...


3

From http://www.mmto.org/history-of-the-telescope/ After nineteen years of productive operations, progress in the production of large mirrors (pioneered at the University of Arizona’s Mirror Lab), and new instrument technologies drove the desire to upgrade the telescope to utilize a single 6.5-m mirror in place of the smaller six-mirror array. The ...


3

Seemingly easy question, but actually not trivial to answer. Wikipedia on H-alpha as well as other entries in other encyclopedias obviously mention the Balmer series and that the spectral line was discovered by Johann Balmer in 1885, but that does not answer your question about the first astronomical observation. The article on the Balmer jump cites a ...


3

Well, to quote wikipedia, it's a matter of personal and historical perspective whom to credit (most): Depending on geographical or historical preferences, the set of the four scientists – Alexander Friedmann, Georges Lemaître, Howard P. Robertson and Arthur Geoffrey Walker – are customarily grouped as Friedmann or Friedmann–Robertson–Walker (FRW) or ...


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