The Day We Found the Universe - Marcia Bartusiak [151]
84 his exposures often ran twenty to forty hours: Slipher (1917b), p. 404.
84 “With such prolonged exposures the accumulation of plates”: LWA, Slipher to Lowell, May 4, 1913.
84 “It is our problem now and I hope we can keep it”: LWA, Slipher to Lowell, May 16, 1913.
85 “My harty [sic] congratulations”: LWA, Hertzsprung to Slipher, March 14, 1914.
85 “It is a question in my mind”: LWA, Slipher to Hertzsprung, May 8, 1914.
85 Slipher inwardly feared … Let the work speak for itself: Strauss (2001), p. 244.
85 confident of what he was seeing: AIP, interview of Henry Giclas by Robert Smith on August 12, 1987.
85 “Spectrographic Observations of Nebulae”: Popular Astronomy 23 (1915): 21– 24.
86 “about 25 times the average stellar velocity”: Ibid., p. 23.
86 his fellow astronomers rose to their feet and gave him a resounding ovation: Smith (1982), p. 19.
86 “Let me congratulate you upon the success of your hard work”: LWA, Campbell to Slipher, November 2, 1914.
87 “I am … glad to have your kind offer”: LWA, Slipher to Edwin Frost, October 22, 1914.
87 enlisted the help of a mathematician: LWA, Slipher Working Papers, Box 4, Folder 4-16.
87 “It has for a long time been suggested that the spiral nebulae are stellar systems”: Slipher (1917b), p. 409.
87 “scattering” in some way: Ibid., p. 407.
87 By 1925, forty-five spiral nebulae velocities were pegged with assurance, and it was Slipher who had measured nearly all of them: Sandage (2004), p. 499.
88 he noticed a particular progression to the stampede outward: Wirtz (1922).
88 a term they labeled K: Use of the K term in spiral nebulae redshift studies was introduced in 1916 by Lick Observatory astronomer George Paddock, who thought the correction would no longer be needed once a sufficient number of observations were made. Others, like Wirtz, swiftly adopted the convention. See Paddock (1916). The K term was actually first used by stellar astronomers. Astronomers were finding that the value for the motion of the Sun, its speed and direction through the galaxy, could change depending on the celestial object—a particular star or nebula—that was used to gauge it. To bring them into agreement, astronomers introduced the K correction term. By the 1960s, with improved measurements, this “K- effect” for stars silently disappeared from the astronomical literature.
6. It Is Worthy of Notice
90 Ancient Persians called the biggest one Al Bakr: The Large Magellanic Cloud was named Al Bakr by the noted Persian astronomer Al-Sûfi in his Book of Fixed Stars, written in 964. While not visible from northern Persia, it was visible to Middle Eastern peoples farther south, near the strait of Bab el Mandeb.
90 “two clouds of mist”: Nowell (1962), p. 127.
91 “capable of doing as much and as good routine work”: Pickering (1898), p. 4.
92 These women “computers” … photographic magnitude: Jones and Boyd (1971), pp. 388–90.
92 “He treated [the computers] as equals in the astronomical world”: Ibid., p. 390.
93 Leavitt grew up in Massachusetts, within a big and supportive family: Johnson (2005), pp. 25–26. Many of the personal details of Leavitt's life are drawn from George Johnson's excellent biography of Henrietta Leavitt, the most comprehensive review of her life to date.
93 “For light amusements, she appeared to care little”: Bailey (1922), p. 197.
94 “For this I should be willing to pay thirty cents an hour”: Johnson (2005), pp. 31–32.
95 “variable-star ‘fiend’”: Ibid., p. 37.
95 one of the first and brightest discovered: The English astronomer John Goodricke first noticed the variable brightness of δ Cephei in 1784. An astronomy prodigy (and also deaf like Leavitt), he won the Royal Society's prestigious Copley medal at the age of nineteen for his work on eclipsing binary stars. He died three years later of pneumonia.
95 “As a rule, they are faint during the greater part of the time”: Leavitt (1908), p. 107.
95 “It is worthy of notice”: Ibid.
97 “A remarkable relation between the brightness of these variables and the length of their periods