Mount Wilson Observatory: The Real Magic Mountain
Mount Wilson Observatory: Where it all came together at last
Five World’s Largest Telescopes in One Place! (1904-1917)
Andrew Carnegie [1835-1919] in 1913
Photograph by Theodore Marceau [1859-1922]
Source: Library of Congress
George Ellery Hale [1868-1938] circa 1908
In the 60-foot Solar Tower Telescope
Carnegie Institution for Science & Huntington Library
The Godfathers of
Big Science
MWO was the first institution
dedicated to astrophysics.
MWO and the Astrophysical
Journal served as the nucleus
for a new community of
astrophysicists.
The Carnegie Institution was founded by Act of Congress in April 1904
It immediately approved a grant of $10,000 ($292,000 in 2020 dollars) to
pay for moving the Snow Solar Telescope from Yerkes to MWO.
It later granted $150,000 ($4,381,000 in 2020 dollars) for use in 1905, to
establish Mt. Wilson Observatory. Another $150,000 came in 1906.
These 5 original staff for
MWO are the principal
actors who laid down the
foundation for the MWO
legacy.
Walter Adams [1876-1956]
Francis Pease [1881-1938
George Ritchey [1864-1945]
Ferdinand Ellerman [1869-1940]
George Hale [1868-1938]
These are the the telescopes of Mt. Wilson Solar Observatory, circa 1910:
The horizontal Snow Solar Telescope (1904/1905 - 1908)
The 60-foot Solar Tower Telescope (1908 - 1912)
The 150-foot Solar Tower Telescope (1910/1912 - 1962)
Dominated solar astronomy & astrophysics 1905-1962
Great Melbourne Telescope (1869-1944) MWO 60-inch Telescope (1908-Today)
48-inch speculum metal mirror 60-inch silver on glass mirror
f/7.6 primary, f/41 cassegrain f/5 primary, f16 cassegrain
f/5 Newtonian & prime focus
f/30 Coudé
Designed for hand/eye sketching Designed for photography
The Great Melbourne Telescope was intended to verify the Southern Hemisphere NGC observations of John
Herschel [1792-1871]. The staff became quite adept at the art of drawing objects. But the drive & mount could not
handle the long exposures necessary for glass plate photography. The telescope deteriorated and was not heavily
used after 1885. But it continued until 1944, when it was moved to Mt. Stromlo and the speculum mirror was
replaced with aluminized Pyrex, and the truss tube re-built. It was destroyed in the 2003 Mt. Stromlo fire.
Yerkes 40-inch refractor (1897-Today) MWO 60-inch Telescope (1908-Today)
40-inch doublet glass lens 60-inch silver on glass mirror
f/19 refractor f/5 primary, f16 cassegrain
About 19 meters (62 feet) long f/5 Newtonian & prime focus
f/30 Coudé
Designed for photography
The Yerkes refractor went into operation in 1897. It was then, and is now, the largest practical refracting telescope
ever made. The 49-inch aperture, 57-meter (187 foot) long, f/46 Great Paris Exhibition Telescope (1900) was fixed
horizontally on the ground, and used a two meter siderostat to see the sky. Chromatic aberration on the 40-inch
made spectroscopy arduous & difficult, requiring each spectral line to be individually photographed. This is a
major reason for Hale wanting to switch to reflectors (see Hale, 1897).
Optical Configurations
for the 60-inch telescope
The coudé light path has
probably been rendered
obsolete by modern echelle
gratings mounted at
Cassegrain or Nasmyth.
But this still needs
verification.
James Lequeux.
The Coudé Equatorials.
Journal of Astronomical History and Heritage, 2011, 14, pp.191-202.
RA
DEC
Moritz Löwy, or Maurice Lœwy (1833-1907)
circa 1871
Coudé telescope, Observatoire de Lyon (1887)
Emmanuel Pécontal
The 100-inch telescope ~1917
Between October 1908 and December 1910, at the St. Gobain
Glassworks in France, 8 tries were made to pour a glass blank
for the 100-inch mirror. But only the 3rd attempt, in December
1908 survived. Initially rejected, this mirror blank, at the time
the largest single piece of glass ever made, was then made
into the 100-inch mirror. George Ritchey worked on grinding
and polishing from 1910 to 1917. The finished mirror is 101” in
diameter, 12.8” thick at the edge, 11.6” thick in the center, and
by itself weighs 9000 pounds. The combination of mirror and
mirror cell together weigh 20,000 pounds.
Physics Laboratory in the Pasadena Offices of Mt. Wilson Observatory
Physics Laboratory in the Pasadena Offices of Mt. Wilson Observatory
An Electric Furnace for Spectroscopic Investigations, with Results for the Spectra of Titanium and Vanadium
Arthur S. King; Astrophysical Journal, vol 28, pages 300-314, November 1908
Highest calibrated
temperature
3015 °C = 5459 °F
Powered by 50 kW
transformer, with
input 2000 V,
providing 5-30 V
at the secondary
Epic Advances in Astronomy: Sun, Stars, Milky Way, and the Universe
Second Paper on the Cause of the Characteristic
Phenomena of Sun-Spot Spectra
George E. Hale & Walter S. Adams
ApJ 25(2) 75-94 (March 1907)
“The presence of the titanium fluting in spots, and their
apparent absence from the ordinary solar spectrum,
strongly confirm the view that the umbral vapors are
cooler than those of the reversing layer.” (page 88)
“The simplest way to account for the relative intensities
of lines in the spectra of sun-spots and third-type stars
is to assume that reduced temperature in these sources
is the effective cause. For, on the one hand, the presence
of the titanium flutings, which consistently rise and fall
in intensity with the flame lines in all of our sources, and
are absent from the solar spectrum, leaves little doubt that
the vapors in sun-spots and third-type stars are cooler than
the corresponding vapors in the reversing layer. On the
other hand, laboratory experiments have shown that
changes of temperature may produce, either directly
or indirectly, just such spectral phenomena as those here
involved. It therefore seems entirely unnecessary to
assume that electrical phenomena, or other such causes,
are at work, though their operation is not necessarily
excluded.” (page 89)
MWO 150-foot (undated)
Carnegie Observatories
28 March 1908 (George Ellery Hale) 30 April 1908 (Ferdinand Ellerman)
First full disk Hα images of the sun
These are the first successful images of the sun in Hα (656.28518 nm) light. Prior to this, beginning in 1892 at Kenwood, Hale
had used a spectroheliograph to image prominences in the Calcium H (396.847 nm; violet) & K (393.366 nm; violet) lines. Later
at Yerkes & Mt. Wilson he imaged the sun in other Balmer series lines: Hδ (410.174 nm; violet), Hγ (434.0462 nm; blue), and
Hβ (486.12786 nm; aqua). Prior to this, there were no photographic emulsions sensitive enough in the deep red color of Hα.
Prior to this, nobody ever saw, nor could have ever seen the sun like this.
Hale noted the exceptional superiority of Hα images and immediately began a program of Hα imaging.
28 March 1908 30 April 1908
Solar Vortices
George Ellery Hale
PASP, vol 20, no. 121, pages 203-220, August 1908
Astrophysical Journal, vol 28, pages 100-116, September 1908
“In view of the fact that the distribution of the hydrogen flocculi frequently resembles that of iron
filings in a magnetic field, it is interesting to recall the exact correspondence between the analytical
relations developed in the theory of vortices and in the theory of hydrodynamics.”
“When observed along the lines of force, many of the lines in the spot spectrum should be double,
if they are produced in a strong magnetic field. Double lines, which look like reversals, have
recently been photographed in spot spectra with the 30-foot spectrograph of the tower telescope,
confirming the visual observations of Young and Mitchell. It should be determined whether the
components of these double lines are circularly polarized in opposite directions, or, if not, whether
other less obvious indications of a magnetic field are present. I shall attempt the necessary
observations as soon as a suitable spot appears on the sun.”
Mount Wilson Solar Observatory, June 20, 1908
Carnegie Observatories
28 March 1908 30 April 1908
Hale found a suitable spot, and observed
both Zeeman splitting, and the oppositely
polarized components on 24 June 1908.
He used the 30-foot spectrograph on the
60-foot tower telescope. This was the first
observation of an extraterrestrial magnetic field.
Solar Vortices (George Hale)
Astrophysical Journal, vol 28, pages 100-116, September 1908
Publications of the Astronomical Society of the Pacific, vol 20, no. 121, pages 203-220, August 1908
Solar Vortices and the Zeeman Effect (George Hale)
Publications of the Astronomical Society of the Pacific, vol 20, no. 121, pages 220-224, August 1908
On the Probable Existence of Magnetic Fields in Sun-Spots (George Hale)
Astrophysical Journal, vol 28, pages 315-343, November 1908
Preliminary Results of an Attempt to Detect the General Magnetic Field of the Sun (George Hale)
Astrophysical Journal, vol 38, pages 27-97, July 1913
Mapping the Magnetic Fields of the Sun (Horace Babcock & Harold Babcock)
Publications of the Astronomical Society of the Pacific, vol 64, no. 381, pages 282-287, December 1952
The Solar Magnetograph (Horace Babcock)
Astrophysical Journal, vol 118, pages 387-396, November 1953
Hale, working with Seth Nicholson, Ferdinand Ellerman, and Arthur Joy, went on to elucidate
the bipolar magnetic structure of sunspots, and to show that the 11½-year sunspot cycle (known
since 1850) was only half of a 23-year magnetic field cycle. A 23-year sunspot cycle had already
been identified by Herbert Turner (Savilian Prof. of Astronomy, Oxford) in 1913
Sun-Spots and Faculae, On the expression of sun-spot periodicity as a Fourier sequence, in similar problems
Herbert H. Turner
Monthly Notices of the Royal Astronomical Society, vol 73, pages 714-732, June 1913
The Magnetic Polarity of Sunspots (Hale, Ellerman, Nicholson & Joy)
Astrophysical Journal, vol 49, pages 153-178, April 1919 (plus 7 plates)
The Law of Sunspot Polarity (George Hale & Seth Nicholson)
Astrophysical Journal, vol 62, pages 270-300, November 1925
Fig. 18 from The Law of Sunspot
Polarity, 1925. The N & S refer
to north or south magnetic
polarity. The R & V refer to
observational red & violet
components in determining
the polarity.
Helioseismology: Discovered via observations on the 60-footsolar tower telescope
Published in 3 papers by Leighton, Noyes & Simon, 1962-1964
Explained as standing waves by Roger Ulrich, 1970
Image from the European Space Agency
Henrietta Swan Leavitt [1868-1921]
Discovered Cepheid period-luminosity�relationship (1908, 1912)
Ejnar Hertzsprung
[1873-1967]
Hertzsprung calibrated
Leavitt’s discovery using
statistical & secular
parallax (1913)
Book:
The Glass Universe
Dava Sobel, 2016
Plots from Leavitt & Pickering, 1912
Harlow Shapley [1885-1972]
American Institute of Physics, Niels Bohr Library
Studies based on the colors and magnitudes in stellar clusters
Twelfth paper: Remarks on the arrangement of the sidereal universe
Astrophysical Journal 49: 311-336 (1919)
Shapley determined the true size
and shape of the Milky Way by
observations on the 60-inch telescope
1914-1919. At the time this was thought
to be the entire universe.
You Are Here
The Center is Here
Determine spectral class (number of lines)
Determine luminosity class (line widths)
Determine absolute magnitude (M) from HR diagram
Determine apparent magnitude (m) by observation
Determine distance from distance modulus
Log10 (d) = 1 + (M-m)/5 [parsecs]
Complication: dimming & reddening of source
due to dust along the line of sight (“extinction”)
Spectroscopic parallax, a method for using stellar
spectra to determine their distance, was first
accomplished by Walter Adams [1876-1956] at
Mt. Wilson, in a series of papers published in the
Proceedings of the National Academy of Sciences
in 1916. In the same year, Adams discovered the
difference between red giant & red dwarf stars,
through their spectra.
The HK Project started at Mt. Wilson in 1966, running on both the 60-inch & 100-inch telescopes, but primarily
on the 60-inch by the 1980s. This was a project to monitor the time-variation of the brightness of stars, specifically
in the H (396.9 nm) & K (393.4 nm) emission lines of the calcium spectrum. The variation in brightness is due to
regions around a sunspot (or starspot) that are exceptionally bright in calcium light. So the data allow the short
term derivation of stellar rotation rates, and long term derivation of star-spot cycles, analogous to our own
11-year sunspot cycle. The project continued until 2002, studying about 2000 stars altogether.
The project discovered that other stars have widely varying starspot cycle periods, including some that are
chaotic, with no obvious period, and some that are quiescent.
Plate H335H
5/6 October 1923
45-min exposure
This is the first Cepheid variable
Hubble observed in M31, and the
first variable star seen outside our
own Milky Way Galaxy.
Hubble recognized it as a Cepheid
class variable star, and knew at
once that he could use Leavitt’s
discovery to calculate an objective
distance to the Great Spiral Nebula
in Andromeda
NGC6822, a remote stellar system
ApJ 62, 409-433, Dec 1925
697,640 LY (today 1,532,000 LY)
A Spiral Nebula as a stellar system: Messier 33
ApJ 63, 236-274, May 1926
857,380 LY (today 2,738,400 LY)
A Spiral Nebula as a stellar system: Messier 31
ApJ 69, 103-158, Mar 1929
896,500 LY (today 2,550,000 LY)
A Relation Between Distance and Radial
Velocity Among Extra-Galactic Nebulae
PNAS 15, 168-173, Mar 1929
Edwin P. Hubble [1889-1953], born in Marshfield, Missouri
When the 100-inch telescope opened in 1917, there was much debate over the true
nature of the “spiral nebulae”, and whether or not the universe and the Galaxy were
actually one and the same thing. Just as Shapley was the first to demonstrate the true
nature of our own Milky Way Galaxy, and the first galactic distance scale, Hubble was
first to demonstrate the existence of an extragalactic universe, and its true distance scale,
through his program of observations using the 100-inch telescope at Mount Wilson
Observatory
Hubble, 1929 Hubble & Humason, 1931
The redshift-distance relationship, a fundamental observational basis
for big-bang cosmology was discovered at Mt. Wilson Observatory
z = (λobs – λrest)/(λrest) = v/c 1 + z = λobs / λrest
z = 0.067
97.8 Mly
Velocities from
Vesto Slipher
unattributed
Slope = H0
Hubble’s Law:
v = H0D
v = recession velocity
D = proper distance
H0 = Hubble constant
H0 usually expressed in units of
(km/sec)/Mpc, so as to return the
relative velocity of a galaxy at a
proper distance of 1 Mpc. But the
distance units cancel out, so the
true unit is sec-1, so the inverse
of H0 is the Hubble time, or the
age of the universe, in the old
standard expanding universe
cosmology.
H0 Age H0 Age
600 1.6308 90 10.87
500 1.7869 80 12.23
400 2.4462 70 13.98
300 3.2615 60 16.31
200 4.8923 50 19.57
100 9.7846 40 24.46
Large values for H0 in the early days of expanding
universe cosmology were a serious problem. Since
the inverse of H0 is the age of the universe, this
resulted in a universe that was uncomfortably young,
to the extent of being younger than the older stars in it.
Baade, 1956 Sandage, 1958
Image: Harvard Smithsonian Center for Astrophysics
Heat radiation of the stars; G.E. Hale & E.F. Nichols; Astrophysical Journal 9, 360-362, 1899.
Ernest Fox Nichols [1869-1924] used a new & improved radiometer to detect stellar infrared at Yerkes
Observatory in 1898/1899, using a 24-inch f/4 mirror made by George Ritchey [1864-1945]. Vega and
Arcturus were observed & detected, albeit with significant uncertainty.
Seth Barnes Nicholson [1891-1963] & Edison Pettit [1889-1962].
Nicholson & Pettit were the first to establish a persistent program of infrared astronomy. Beginning in
1921 at Mt. Wilson Observatory, they used a thermocouple at the focus of the 100-inch telescope to make
infrared measurements of Mercury, Venus, Mars, the sun, the moon and about 100 stars. Their most
surprising discovery was that Venus was hot, and that the day & night temperatures were the same.
Nevertheless, infrared astronomy did not enter
the mainstream of astronomy until after the post
WWII success of radio astronomy, and advances
in the technology for infrared detectors.
The 100-inch telescope
Mt. Wilson Observatory
circa 1917.
From the Huntington
Library Archives.
Carnegie collection at Huntington Library
62-inch, f/1, wide field telescope with aluminum coated,
spin-cast epoxy-resin mirror, on display at the Space Science
Exhibition, at the Steven F. Udvar-Hazy Center, Chantilly,
Virginia. Used to conduct the world’s first all sky infrared
survey, at Mt. Wilson Observatory
Observations of Extremely Cool Stars
Neugebauer, Martz & Leighton
Astrophysical Journal, vol 142, pp. 399-401, July 1965
Two-Micron Sky Survey – A Preliminary Catalog
G. Neugebauer and R.B. Leighton
NASA SP-3047, August 1969
The world’s first infrared sky survey, covered 2 IR bands:
0.68-0.92μm & 2.01-2.41μm. The 62-inch telescope had an
angular resolution of 2 arc-minutes. The final source catalog
includes over 5,000 stars.
The survey was carried out at Mt. Wilson, Calif. having a 62-inch
diameter and an f/1 aluminized epoxy mirror mounted equatorially.
Radiation at an effective wavelength of 2.2μ was detected by lead
sulfide photoconductive cells cooled by liquid nitrogen and located
at the prime focus of the mirror. Eight lead sulfide cells, each
subtending about 10’ north-south by 3’ east-west, were arranged in
an array whose overall dimensions were 40’ north-south and 6.5’
east-west. The effects of terrestrial background radiation were
minimized by vibrating the mirror at 20 hertz so that an image of a
point source oscillated in the east-west direction and fell alternately
on one or the other of two adjacent cells. Only the alternating signal
was amplified, thus eliminating the nonvarying background. It
should be noted that this method of chopping effectively measures
the second derivative of the source intensity and thus discriminates
against smoothly varying extended sources. … The strip chart
recordings were digitized for processing with the IBM 7094
computer of the Caltech Computing Facility.
Observations of an Infrared Star in the Orion Nebula
Becklin, Neugebauer
Astrophysical Journal, vol 147, pp. 799-802 (February 1967)
Discovery of an Infrared Nebula in Orion
Kleinmann, Low
Astrophysical Journal Letters, vol 149, no. 1, part 2, pp. L1-L4
(July 1967)
The Becklin-Neugebauer object was discovered in a survey
of the Orion Nebula using a dual-beam photometer attached
to the cassegrain focus of the 60-inch telescope. It is the first star
ever discovered using infrared, and completely invisible in
visible light.
The Kleinmann-Low Nebula was discovered in the data from
the same survey that revealed the BN object, supplemented
with data from the University of Arizona. It is essentially the
infrared core of M42, the visible light Orion Nebula.
The successful northern sky survey, plus the discoveries in the
Orion Nebula, provided a major impetus for the advance of
modern infrared astronomy. Astronomers had been observing
infrared since the mid 1800s, but it was always a very small,
cottage industry. Just as MWO had earlier brought astrophysics
into the open, it now brought infrared astronomy into the open.
The Becklin-Neugebauer Object (V 2254 Ori, 2MASS J05351411-0522227)
Infrared K-band (2.2 μm) image from the ESO Very Large Telescope.
Robert J. Vanderbei
Princeton University
2-min stack, deconvolved
The Distance to the Orion Nebula
Menten, et al.; A&A 474(2): 515-520 (Nov 2007)
BN object
Interferometer light path
Measurement of the diameter of α Orionis with the interferometer
A.A. Michelson & F.G. Pease; ApJ 53: 249-259 (May 1921)
Albert Michelson used astronomical
interferometry for the first time at
Lick Observatory, to measure the
angular diameter of Jupiter’s moons
(1891). The measurements made at
MWO were the first stellar angular
diameter measurements ever made.
They were made with a 20-foot beam
attached the the 100-inch telescope,
beginning in 1920.
Mount Wilson Observatory Today
CHARA Array, optical interferometer, Center for High Angular Resolution Astronomy, Georgia State University
planning 1985, construction 1996-2003; 330 meter (1083 foot) max baseline; 0.2 milliarcsecond resolution
World’s Largest Optical Interferometer: Center for High Angular Resolution Astronomy (CHARA), Georgia State University
Groundbreaking 13 July 1996; Dedication 4 October 2000; First science observations in spring, 2005
Beam
Combining
Facility
One of six 1-meter
(40-inch) CHARA
telescopes
Dr. Hal McAlister
Rapid rotators imaged with the MIRC beam combiner at the CHARA Array. Image courtesy of John Monnier.
3.8 Ms 2.4 Ms 1.9 Ms 2 Ms 2 Ms
4.3 Rs 2.6 Rs 2 Rs 2.8 Rs 3.5 Rs
316 Ls 25 Ls 11 Ls 17 Ls 27 Ls
16 h 14.5 h 7.8 h 12 h 21.4 h
80 ly 49 ly 17 ly 49 ly 55 ly
The expanding fireball of Nova Delphini 2013
Gail Schaefer, et al.; Nature 515(7526): 234-236, November 2014
The angular expansion
rate, combined with
radial velocity gives
a geometric distance
4.54 ± 0.59 kpc =
14,800 ± 1,900 ly
Most likely explosion
model has a optically
thick core surrounded
by an optically thin
envelope.
Infrared images of the transiting disk in the ɛ Aurigae system
Brian Kloppenborg, et al., Nature 464(7290) 870-872, April 2010
Known to be variable with ~27 year period since circa 1830. Gaia distance 1350 ± 300 ly.
Dimming lasts ~ 640-730 days (1.7 – 2.0 years). Long time mystery, but suspected to be
dust disk surrounding companion. Verified by CHARA.
Most likely F-class primary, B-class secondary embedded in disk (could be binary too)
Horace Welcome Babcock [1912-2003]
Godfather of Adaptive Optics (1953)
Photo: American Institute of Physics
A
Cast
of
Characters
George Ellery Hale [1868-1938] Kenwood Observatory, Chicago John A. Brashear [1840-1920]
circa 1886
A few years ago somebody commenced a correspondence with me by the name of George E. Hale. From the
method of his writing, from his correspondence, I judged him to be a man of about 45, and to certainly be well
up in the astronomical business, and, strange to say I had not heard of him through any of the books. One day,
after I had furnished this same gentleman, living in Chicago, quite an amount of apparatus, there stepped into
my shop a young fellow. I looked at him. He seemed to be very quiet and modest, and I thought: Well, there is
another fellow wants a job as an apprentice. He came up to me and introduced himself as Mr. Hale from Chicago.
Well, if somebody had taken a baseball bat and hit me very, very hard I should not have been any more surprised.
I took a liking to the fellow at once, and if he had been a lady I should like to have proposed, but he wasn’t, and I
was married anyway.
John A. Brashear, Chicago newspaper clipping, 16 June 1891, Niels Bohr Library
Harlow Shapley [1885-1972]
American Institute of Physics, Niels Bohr Library
Thermokinetics of Liometopum apiculatum Mayr
Proc. Natl Acad. Sci. USA 6, 204–211 (1920)
Preliminary report on pterergates in Pogonomyrmex Californicus
Proc. Natl Acad. Sci. USA 6, 687–690 (1920)�
Note on pterergates in the Californian harvester ant
Psyche 27, 72–74 (1920)�
Note on the thermokinetics of Dolichoderine ants
Proc. Natl Acad. Sci. USA 10, 436–439 (1924)
Plot courtesy PNAS
Ant image from Discovering Life
Harlow Shapley [1885-1972]
American Institute of Physics, Niels Bohr Library
Plot courtesy PNAS
Ant image from Discovering Life
The Harlow Shapley Project
https://harlowshapley.org/
Deborah Shapley, Granddaughter
Photo from the Indiana Basketball Hall of Fame
Hubble was inducted into the Indiana Basketball Hall of Fame in 2017
Helm’s Foundation National Champions 1906-1907, 1907-1908 & 1908-1909
Western Conference (Big Ten) Champions 1909-1910 (pictured here)
Arthur Scott King [1876-1957]
Arthur King received the first PhD in physics ever awarded
by the University of California at Berkeley, in 1903. After
spending 2 years studying spectroscopy in Germany, he
returned to UC Berkeley as an instructor on 1905. At the
invitation of George Hale, King joined the staff of MWO
on January 1st, 1908, as the head of the physics laboratory.
He remained as director until he retired in 1943.
King designed the spectroscopes, the high temperature
electric furnace, and directed the extensive program of
spectroscopy in the physics laboratory. He made extensive
study of the spectra of atoms and molecules at varying
temperatures. Along with Harold Babcock [1882-1968],
they employed a 35,000 Gauss magnetic field to study
Zeeman splitting of spectral lines. It was King’s laboratory
spectroscopy that provided the physical verification for
the low temperature of sunspots, and the discovery of
magnetic fields on the sun.
In 1929, using the electric furnace, in collaboration with
Berkeley physicist Raymond Birge [1887-1980], they discovered
the isotope 13Carbon, which makes up about 1.1% of all
natural carbon, and is the only stable isotope other than
12Carbon.
100 years since first light on the 100-inch – 1/2 November 1917 about 2 AM
Log book entry by night assistant Wendell Hoge
Alfred Noyes [1880-1958],
National Portrait Gallery, London
Watchers of the sky (1922); first volume of the 3 vol
set, The Torch Bearers
High in heaven it shone, alive with all the
thoughts, and hopes, and dreams of man’s
adventurous mind.
Up there I knew, the explorers of the sky,
the pioneers of science, now made ready to
attack that darkness once again, and win
new worlds.
Tomorrow night they hoped to crown the toil
of twenty years, and turn upon the sky,
the noblest weapon ever made by man.
Mount Wilson Observatory www.mtwilson.edu
Supplementary slides follow for Q&A
Harvard College Observatory tested Mt. Wilson as a
prospective observatory site 1889/1890, the same year
that Hale was also at HCO. But they left after encountering
the worst mountain winter for nearly a century.
HCO Director (1877-1919) Edward Pickering [1846-1919]
made arrangements with USC and trustee Edward Spence
[1832-1892] to build a larger observatory at Mt. Wilson,
near what is now the main parking lot, with a 40-inch lens
made by Alvan Clark & Sons.
But Spence died without leaving the money for the new
observatory, so the whole plan fell through. The 40-inch
2-element lens went to Yerkes Observatory.
13-inch telescope for Harvard College Observatory
test site at Mt. Wilson. Telescope mount tilted to
compensate for latitude difference between Mt.
Wilson and Harvard. After HCO withdrew from
Mt. Wilson, this telescope was transferred to Boyden
Observatory, near Bloemfontein, South Africa, and
is now used for public outreach astronomy.
George Ellery Hale [29 June 1868 – 21 February 1938]
Niels Bohr Library, American Institute of Physics
1850 – Clausius and the 2nd law
1859 – Kirchoff & Bunsen & spectroscopy
1865 – Maxwell’s “Dynamical Theory”
1868 – GEH is born
1870 – Homer Lane on solar interior
1873 – Maxwell’s Treatise�1877 – Boltzmann Entropy
1886-1890 - MIT
Kenwood Observatory, Carnegie collection at the Huntington Library
Kenwood Observatory, 1891-1895
12-inch Clark 1892
George Ellery Hale [29 June 1868 – 21 February 1938]
Niels Bohr Library, American Institute of Physics
circa 1886
1889 – GEH invents spectroheliograph
1890 – Kenwood Observatory
1891 – Prof. of Astrophysics, Beloit College
1892 – Yerkes Observatory established
1893 – Studies spectroscopy in Berlin
1893 – Assoc. Prof & full prof (1897) U of Ch.
1897 – Yerkes Observatory opens�1904 – MWO established & opened
Kenwood Observatory, Carnegie collection at the Huntington Library
Kenwood Observatory, 1891-1895
12-inch Clark 1892
1892-1897: Yerkes Observatory, Williams Bay, Wisconsin
George Ellery Hale was already an
experienced astronomer and founder of
observatories, with a global reputation,
before coming to Mt. Wilson.
Hale received his bachelor’s degree in
physics from M.I.T. (1886-1890), and had
worked at Harvard College Observatory
(1889-1890) under Edward Pickering.
Photograph dated December 1910, from the
Carnegie Institution for science collection at
the Huntington Library in San Marino, CA.
Rumford Spectroheliograph, Yerkes Observatory, 1903
Funded by the Rumford Committee
Hale Spectroheliograph, Kenwood Observatory, 1892-1895
Photographs from the Carnegie collection at the Huntington library
Hale invented the spectroheliograph in 1889, but did not get
one to work well enough until 1892.
Walter Baade [1893-1960] in 1955 (MWO)
The Resolution of Messier 32, NGC 205 and the Central Region
of the Andromeda Nebula
The Astrophysical Journal 100: 137-147 (September 1944)
The Period-Luminosity Relation of the Cepheids
Publications of the Astronomical Society of the Pacific 68(400): 5-16
(February 1956)
Observing with the 100-inch telescope at Mt. Wilson Observatory in
1943, Baade was the first to resolve the two companions of M31, as
well as the central bulge of M31 into stars. His observations revealed
two different populations of stars, which Baade called type I and
type II, where type I is mostly luminous O & B stars and open clusters,
while type II refers to globular clusters and cluster variables.
Baade later expanded this work with the 200-inch telescope at Palomar
Observatory, proving the existence of two types of Cepheid variable,
announced at the 1952 meeting of the IAU in Rome, and described in
the 1956 paper.
The discovery that there are two types of Cepheids instantly doubled
the perceived size of the universe by correcting the period-luminosity
relation used by Shapley & Hubble to determine distances. It also fixed
the age dilemma by making the universe now older than the oldest
stars.
Physics laboratory at Mt. Wilson Observatory. The laboratory was later moved
to Pasadena, where higher electrical power, and more room, could be provided.
1904:
Mule train carrying parts of the Snow Solar Telescope to Mt. Wilson.
Named by Helen Snow for her father, the telescope was loaned to
Hale by Yerkes Observatory. This was the first research telescope on
Mt. Wilson, and became the world’s largest, and most effective
solar telescope.
Couple-Gear electric truck
Couple-Gear Freight-
Wheel Company,
Grand Rapids, MI
A little excitement along the way
July 1st 1917
Carnegie collection at Huntington Library
Assembling the 100-inch telescope
The Solar Spectrum showing the Fraunhofer lines
Light is the fundamental observational property of stars
Spectroscopy is the fundamental observational tool of astrophysics
The
Zeeman
Effect
Pieter Zeeman
Albert Einstein
Paul Ehrenfest
circa 1920
Zeeman disobeyed
instructions in 1896
not to use lab for
measuring line splitting
in magnetic fields.
Shared 1902 Nobel
Prize in physics
anyway.
The absorption / emission lines in the hydrogen spectrum come in well known and predictable series,
the energies of which depend on the Bohr model orbital transitions as diagrammed here.
The lower energy Brackett & Pfund series are not shown.
(Again)