--- "R. William Gosper" <rwg@spnet.com> wrote:
... The remainder of this contribution is quotes from that 7th grade Prentice Hall "astronomy" book, with my comments and questions in [brackets].
p17. You are completely uprepared for the spectacle that awaits you when you put on your glasses. To your left you notice a mass of brilliant stars that shine mainly with X-rays. [Gee, then how come the Hertzsprung-Russell diagram (p34?) only goes up to blue on the temperature scale?]
The Hertzsprung-Russell diagram predates space-based astronomy. The atmosphere blocks wavelengths shorter than about 300 nm. I belive there are object that shine mainly in X-rays, but the emission mechanisms are nonthermal, and thus outside the scope of the H-R diagram.
... --rwg PS, July 2 is the 36th anniversary of X-ray astronomy, inadvertently initiated by US spy satellites. Absent gamma ray bursts, what's the next best evidence for black holes?
Using doppler shift, we determine the velocity of stars as a function of distance from the galactic center. That allows us to calculate the enclosed mass. __________________________________ Do you Yahoo!? Yahoo! Calendar - Free online calendar with sync to Outlook(TM). http://calendar.yahoo.com