Biographical Memoirs Volume 90 (2009) / Chapter Skim
Currently Skimming:
HORACE WELCOME BABCOCK
HORACE WELCOME BABCOCK
Pages 16-53
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 16... ...
Photograph by Mount Wilson and Los Campanas Observatories
|
From page 17... ...
Harold met Horace's mother, Mary Henderson, in Berkeley during his student days at the College of Electrical Engineering, University of California. After brief appointments as a laboratory assistant at the National Bureau of Standards in 1906 and as a physics teacher at the University of California, Berkeley, in 1907, Horace's father was invited by George Ellery Hale in 1908 to join the staff of the Mount Wilson Observatory (MWO)
|
From page 18... ...
In his oral interview for the American Institute of Physics (AIP) Horace recalls that many of his childhood recollections relate to Mount Wilson, seeing the astronomers, being aware of construction on the mountain, in particular "the noisy riveting of the 100-inch dome.
|
From page 19... ...
O M E B A B C O C K HORACE WELC 19 150-foot solar tower on Mount Wilson, where he produced spectrograms of the solar chromosphere, especially in the infrared. He published five short papers about these activities in the Publications of the Astronomical Society of the Pacific (one with his father)
|
From page 20... ...
. It was dominated by several big names in "theoretical astronomy," a term which at that time in Berkeley meant "orbit theory." Horace had already been exposed to the new astrophysics that Hale had made the centerpiece of research at the Mount Wilson Observatory, but only Donald Shane, subsequently director of Lick Observatory, taught astrophysics at Berkeley in 1935.
|
From page 21... ...
They are displayed in his thesis, published as Lick Observatory Bulletin, No. 498 in October 1939 and now reproduced in a more readily available journal Publications of the Astronomical Society of the Pacific, volume 116.
|
From page 22... ...
Upon converting his radial velocities to angular velocities about the center of M31, Horace noted in his thesis that "the obvious interpretation of the nearly constant angular velocity from a radius of 20 minutes of arc outward is that a very great proportion of the mass of the nebula must lie in the outer (dim) regions." In retrospect we now know that Horace had come upon the crucial evidence for the existence of dark matter, but like Wegener's continental drift, it was a discovery before its time.
|
From page 23... ...
He used a small spectrograph put together around a fast Schmidt camera and a grating provided by his father, who was in charge of the MWO grating laboratory at that time. He and Josef Johnson, a graduate student working with Caltech astrophysicist Fritz Zwicky, took spectra of the night sky, which they continued through the year.
|
From page 24... ...
; his father, now supervisor of the Mount Wilson grating laboratory, was able to provide one for him.
|
From page 25... ...
George Van Biesbroeck, the astronomer in charge of the shop, modified the plans, probably to simplify the work, before handing them over to Ridell, and neither Van Biesbroeck nor Struve felt called upon to notify Horace of the changes. He learned of them only when the parts arrived at the remote McDonald observing site, where the instrument could not be assembled and used effectively.
|
From page 26... ...
, with perhaps a stop at the last big prewar American Astronomical Society meeting at Yerkes (in September 1941) , and then on to Cambridge.
|
From page 27... ...
In the Caltech Rocket Project he became reacquainted with Ira S Bowen, the Caltech physics professor about to assume the directorship of the newly formed Mount Wilson and Palomar Observatories, whom he had met earlier at Lick.
|
From page 28... ...
STELLAR MAGNETISM While completing his microphotometer assignment, Horace also chose his first venture into scientific research at the Mount Wilson and Palomar Observatories.
|
From page 29... ...
" By way of justification for such a notion he imagined that strong fields might be generated by some dynamo process in rapidly rotating stars: "I really did have the notion that rapid rotation would somehow result in strong magnetic fields." Accordingly, he estimated the stellar field strengths that might exist if magnetic field strength scaled with rotation. The sun with a general field of 50 gauss (the erroneously high but accepted value at that time)
|
From page 30... ...
The iron arc spectra (containing myriads of Fe I emission lines of known wavelengths) established a coordinate system on the photographic plate within which it was possible to measure the small wavelength shifts between the two polarized spectra that signaled the presence of a magnetic field.
|
From page 31... ...
Horace took his analyzer to the Mount Wilson 100-inch telescope and during his first experimental run discovered a believable magnetic field of ~1 kilogauss in the sharp-lined peculiar A-type star 78 Virginis. All of his expectations were fulfilled with unanticipated speed.
|
From page 32... ...
Periodic magnetic variability has proven to be invariably the rule among the A-type stars, whenever field strengths significantly exceed the errors of measurement, and the periods are invariably the periods of spectrum variation, a phenomenon known since the beginning of the 20th century. In the course of his investigations Horace also discovered the crossover effect, the appearance of peculiar line profiles that occurs in some stars at phases when the magnetic field reverses polarity.
|
From page 33... ...
However, so far as I can ascertain Horace never accepted the Oblique Rotator interpretation of his data, arguing as late as 1958 that strong, coherent magnetic fields are a property of rapidly rotating stars, detectable only in that small proportion of such stars that happen to be observed pole-on. I attribute his preference for an explanation couched in hydromagnetic oscillations to his intimate familiarity with the complex details of solar magnetism (more of this below)
|
From page 34... ...
Thus, Horace's efforts were part of a major thrust in solar physics at Mount Wilson that began with George Ellery Hale's discovery of magnetic fields in sunspots at the 60-foot solar tower a half century earlier. Horace's contributions to these seminal developments were several-fold: (1)
|
From page 35... ...
Today advanced technologies for the measurement of solar magnetic fields have proliferated at Big Bear Observatory in California; at the National Solar Observatory; at a complex of European facilities at Observatorio del Teide in the Canary Islands; and at solar observatories in Crimea, Japan, Russia, Ukraine, and elsewhere. Horace Babcock really started something.
|
From page 36... ...
His very important 1951 paper on the periodic reversing magnetic field and associated crossover effect of HD 125248 is accompanied by a report in the same year on the performance of the Mount Wilson ruling engine, which Horace supervised, and the quality of diffraction gratings produced by it. In 1953, while preparing a paper about the magnetograph and its use, he also published a seminal paper entitled The Possibility of Compensating Astronomical Seeing, a description of procedures by which it might be possible to produce diffraction-limited images of celestial sources at ground-based telescopes.
|
From page 37... ...
Typically, Hale imported physicist John Anderson from Johns Hopkins University in 1912 to make very large gratings for the Mount Wilson telescopes. In 1929 after Anderson had taken charge of the 200-inch project, Harold Babcock succeeded him in the MWO grating laboratory, replacing Anderson's original ruling engine with a more compact machine.
|
From page 38... ...
Horace Babcock became director of the Mount Wilson and Palomar Observatories on July 1, 1964. This path from science into administration strongly parallels that of a predecessor, Walter Adams.
|
From page 39... ...
He served as astronomer in charge of testing and acceptance of the du Pont telescope mirrors and for two years beginning in 1976 as assistant director for Las Campanas. Vaughan delivered his remarks at the Babcock Memorial Symposium held on the Caltech campus on May 21, 2004.
|
From page 40... ...
Tuve, later communicated to President Haskins and the trustees, arguing that the institution should build a major observatory in the Southern Hemisphere, and stressing the antiquated condition of the institution's Mount Wilson Observatory. Maybe that letter was influential.
|
From page 41... ...
. The AURA land includes several major peaks, the largest being Cerro Tololo, Cerro Morado, Cerro Pachon, and Cerro Cinchado.
|
From page 42... ...
Horace and his staff and the Carnegie Institution's officers had high hopes that the Ford Foundation would provide the necessary funds to build Carnegie's Southern Hemisphere 200-inch telescope, but by the end of 1966, it had become clear that Ford Foundation funding for a Carnegie southern 200-inch
|
From page 43... ...
The attendees were Robert Kraft, Olin Wilson, Armin Deutsch, Allan Sandage, Henrietta Swope, and Arthur Vaughan, with Horace chairing the meeting. Horace explained to the staff that Carnegie trustees had earmarked $2 million for a joint Carnegie-Caltech astronomy building on the Caltech campus, but that if a decision could be reached to proceed with a southern observatory, the institution might have a serious problem in providing its share of the funding.
|
From page 44... ...
Babcock and John Irwin, who ran the site testing program in Chile, summarized their conclusions in an unpublished memorandum: In 1968 it became clear that Las Campanas came closer than any other site in meeting the prescribed CARSO criteria: 29 degree S latitude; 7500-8300 feet elevation, with ample space for many telescopes; only 40 miles from the coast and well-separated from the cordillera; good topography, with no mountains to windward; no prospect of future light pollution; easy road construction; ready availability for purchase; and, as confirmed by test wells, adequate water sources. In September 1968 Horace wrote to Ackerman that in view of the lack of substantial progress in his attempts to deal with AURA, he [Babcock]
|
From page 45... ...
The upshot of all this was that Horace Babcock and Allan Sandage met with Mrs. Greenewalt at Carnegie headquarters in Washington to answer questions she posed.
|
From page 46... ...
After seven years of traveling, testing, and talking, Horace aided by only a few close associates had finally set Las Campanas Observatory on its course. Soon thereafter, Horace created the Las Campanas Observatory Committee, which included Bruce Rule as chief engineer, Ed Dennison in charge of electronics, J
|
From page 47... ...
First, the decision to create Las Campanas Observatory was viewed with dismay by some Caltech astronomers, most notably by Jesse Greenstein, who worried that the new facility would put Carnegie and Caltech into a competition for foundation money in which both institutions would lose. Jesse would have preferred to see the Carnegie Institution invest its astronomical resources at Palomar Observatory, so that it could better compete with well-funded national (AURA)
|
From page 48... ...
Such issues may have bothered Horace as well, but they did not weaken his resolve to complete Las Campanas Observatory. Thirty years later these concerns are largely forgotten, indeed unknown to the present generation of astronomers, but they seemed very important in 1975, and they should be acknowledged in considering the impact of Horace Babcock's drive to create Las Campanas Observatory.
|
From page 49... ...
Horace won worldwide acclaim for his contributions to astronomy. Following his election to the National Academy of Sciences in 1954, he was the recipient of the Henry Draper Medal of the Academy in 1957, the Eddington Medal of the Royal Astronomical Society in 1958, the Catherine Wolfe Bruce Medal of the Astronomical Society of the Pacific in 1969, the Gold Medal of the Royal Astronomical Society in 1970, and the George Ellery Hale Medal of the Solar Physics Division of the American Astronomical Society in 1992.
|
From page 50... ...
. in preparing this memoir I borrowed from presentations of Donald Osterbrock and Arthur Vaughan delivered at the Babcock Memorial Symposium held at Caltech on May 21, 2004.
|
From page 51... ...
110:126 142. Stellar magnetic fields and rotation.
|
From page 52... ...
Sky Telescope 54:90. 1986 Diffraction gratings at the Mount Wilson Observatory.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.