This Month in the History of Astronomy - February
- Feb 4, 1906 - Clyde Tombaugh, who discovered Pluto
in 1930 (see below).
- Feb 7, 1824 - William Huggins, pioneer British spectroscopist
and astrophysicist, whose science was decades ahead of his equipment.
Using a backyard observatory 8" refractor located outside London and
visual observations he first showed (1863) that the spectra of stars
revealed them to be made of the same elements as were known to the
chemist in the laboratory, and that stars were dense, incandescent
objects surrounded by a cooler but still hot atmosphere of gas.
Next (1864), he turned to the 'nebulae', some of which had been
resolved into clusters of stars with better telescopes, and found
the one in Draco now known as NGC 6543 had, instead, an emission
line spectrum, indicating a luminous cloud of hot, rarefied gas,
He then discovered two new emission lines in the Orion Nebula, and
proposed a previously unknown element ("nebulium") since these had
not been seen in the laboratory. It would be 63 years before these
were recognized by Ira Bowden as 'forbidden' lines of ionized
nitrogen and oxygen requiring conditions so close to a perfect
vacuum that they couldn't be created artificially in the lab.
Observing the nova of May 18, 1866, he saw a composite spectrum,
with emission lines superposed on a stellar spectrum, indicating
the brightening was accompanied by the expulsion of gas hotter
than the star. This was also the first observation of carbon
bands in the spectrum of a nova. Decades later it would be
understood this was the result of nova of this sort occurring in
close binary systems where the progenitor is a carbon rich white
dwarf star -- essentially the core of a burned out red giant star
which has fused all its hydrogen into helium and then all its
helium into carbon (and oxygen) before loosing its outer layers.
Huggins next (1868) turned to the spectral Doppler shift and tried
to make a radial velocity measurement for a star, using the F line
of hydrogen in the spectrum of Sirius. Due to his relatively crude
equipment and its low wavelength resolution the measurement was
beyond his capability, and he got an answer that was almost 10x
too high, but the velocity of 170,000 kilometers per hour was
incredible for the time. That same year he observed a comet and
ID'd the lines in its spectrum as indicating the presence of
hydrocarbons (see also Aug 5).
During the next ~30 years he developed an ultraviolet spectrograph
-- early photographic emulsions were only sensitive to short
wavelength UV and blue light -- and in 1899, with his wife, he
published an Atlas of Representative Stellar Spectra. From
1900-05 he was president of the Royal Society.
- Feb 7, 1889 - The Astronomical Society of the Pacific,
first national astronomy organization.
- Feb 11, 1911 - Carl Seyfert, American astronomer known
for first studying and calling attention, in 1943, to active
galactic nuclei (centers of galaxies) found in a small percentage
of spiral galaxies now named after him as a class, as well as an
unusual grouping of galaxies in which one member has a discrepant
radial velocity, 5x that of the other five galaxies, now known as
Seyfert's Sextet (1951).
Seyfert galaxies have very bright, usually bluish cores which have
a high excitation, non-thermal, emission spectrum and their broad
lines suggest gas (or cloud) motions of several thousand kilometers
per second (-for Type I's, 10x less that for Type II). The brightness
of these galactic nuclei can also be variable on time scales of years.
In many ways, Seyfert nuclei resemble quasars, being at the lower end
of an energy spectrum which makes the latter visible at much greater
NGC 1068, in 1908, was first such galaxy noticed, by Edward A. Fath
and Vesto Slipher at the Lick Observatory, to have bright emission
lines (six of them), and both it and two other such galaxies were
studied by Edwin Hubble in 1926.
- Feb 13, 1852 - J.L.E. Dreyer, Danish-born Irish astronomer who
compiled the New General Catalogue (NGC) published in 1878, the last
such catalog of "fuzzy objects" across the sky which was made with
visual observations before photography became widely applied in
- Feb 14, 1898 - Fritz Zwicky, who 1st identified supernovae as
a separate class of objects and suggested the possibility of both
neutron stars and dark matter.
Zwicky was the first astronomer to observe on Mt. Palomar and was
the father of the Sky Survey technique. He almost single-handedly
constructed the wide field 18" Schmidt camera to search for SNe,
and he discovered over 100 with it, as well as gathering the first
evidence for dark matter from observations of clusters of galaxies.
The famous Comet Shoemaker-Levy 9 (which crashed into Jupiter) was
discovered with this instrument in 1993.
He also designed both solid rocket motors and missile guidance systems
during WWII for the early southern California aerospace industry.
Zwicky was adamantly Swiss, even though he lived and worked in
Pasadena for forty years, and was the first non-U.S. citizen ever
to be awarded the Medal of Freedom (by Truman): he was one of only
a handful of scientists at his level sent to investigate both the
German V-2 rocket factories and the aftermath of Hiroshima/Nagasaki
immediately following the end of the war.
- Feb 14, 1904 - Boris Vorontsov-Vel'laminov, Russian astronomer
who, independently of Trumpler in the U.S., demonstrated the absorption
of starlight by interstellar dust in 1930. From 1934 on he was a
professor at the University of Moscow, where he authored several
excellent textbooks, at both the introductory and advanced levels.
Besides work on gaseous nebulae (especially planetary nebulae), novae,
the Hertzsprung-Russel diagram, massive hot stars, and the evolution
of stars in general, he's probably best known now for his 1959 catalog
of 350 perturbed and presumably interacting close pairs of galaxies,
which are still sometimes seen designated by their "VV" numbers; his
more general 1962 catalog listed 30,000 galaxies.
- Feb 15, 1564 - Galileo Galilei, first scientist to use
a telescope for astronomical observation, making many important
discoveries. (see Jan 4)
- Feb 16, 1786 - Francois Arago, pioneer scientist in the
wave nature of light and the inventor of the polarimeter and other
- Feb 19, 1473 - Nicholas Copernicus, creator of the modern
solar system by showing how the retrograde motion of the outer planets
was a natural feature of a system in which the planets go around the
- Feb 20, 1844 - Ludwig Eduard Boltzmann, Austrian physicist
and namesake of the constant "k". Boltzmann's work on the kinetic
theory of gases (statistical mechanics) tells us how the properties
of matter on a small scale determine macroscopic properties like
temperature and pressure.
In 1869 in Heidelberg he worked with Robert Bunsen (of Bunsen burner
fame) and then, in 1871, with Gustav Kirchhoff and Hermann von
Helmholtz in Berlin, two greats in the history of thermodynamics.
He became Professor at the University of Graz and taught later
chemistry greats Svante Arrhenius and Walther Nernst; it was also
here that he developed his statistical concept of matter, quantum
physics and atomic theory being yet a decade or two still in the
future. Later, as professor in Vienna, he had Paul Ehrenfest and
Lise Meitner as students.
In 1906 Boltzmann hanged himself. His tombstone bears the inscription
of his entropy formula (second law of thermodynamics):
S = k · log W
In galaxy dynamics the collisionless Boltzmann equation,
df/dt=0, expresses the idea that the flow of the probability fluid,
which can be used to represent stars, through phase space is
- Feb 22, 1824 - Jules Janssen, French astronomer and
solar spectroscopist, who was director of the new (1875)
observatory at Meudon for the next 30+ years.
Previously, having heard about Kirchoff's 1859 identification
of terrestrial elements in spectra of the Sun, Janssen launched a
study of the dark bands in the Sun's spectrum, now called
"telluric rays", and showed they were of terrestrial origin,
varying with both altitude and humidity, as well as the path
length through the atmosphere ("air mass"), at the time of
observation. In 1867 he used similar techniques with a telescope
in the Azores to first discover water vapor in the atmosphere of
Janssen was part of the scientific team at the historic eclipse
in India in 1868 (Aug 18), noting a third yellow emission line
in the spectrum of the chromosphere (the first two being due to
sodium), which British astronomer and spectroscopist Norman
Lockyer virtually simultaneously with Janssen proposed must
be due to an unknown element in the Sun, called helium, but
not found on earth for another three decades.
That same year he developed a spectrohelioscope for studying
the Sun during the daytime and without an eclipse, and
established an observatory on Mount Blanc to minimize the
effects of the earth's atmosphere, the beginning of a trend
in siting telescopes on mountaintops, which now seems
self-evident. Janssen's photographic atlas of the Sun
(1904), about the first of its kind, was based on observations
covering 28 years.
- Feb 26, 1842 - Camille Flammarion, prolific and widely
read 19th century popularizer of astronomy and the notion of there
being extraterrestrial life.
- Feb 27, 1897 - Bernard Lyot, inventor of the coronagraph
Discoveries and other firsts
- Feb 3, 1966 - First soft landing on the Moon, by Soviet Luna 9.
- Feb 5, 1963 - The first quasar redshift was measured, by
Maarten Schmidt, who was seeking optical identification of radio
sources. Hence the quasar is named 3C 273 (#273 in the 3rd Cambridge
catalog of such sources), and it had an unimaginably high redshift
of z=0.158 (47,400 km/sec) for the time. It was only shortly later
that Jesse Greenstein, also working with spectra taken with the 200"
telescope at Mount Palomar, found 3C 48 to have z=0.37, thus clinching
the case for quasars (which is short for "quasi-stellar radio source")
being an extraordinary class of objects.
- Feb 5, 1974 - Mariner 10 makes the first close-up photos
- Feb 6, 1971 - Both the first color TV pictures were sent
back from, and the first golf shots were taken on, the Moon, by
Apollo 14 astronauts (Alan Shepherd in the latter instance).
- Feb 6, 2011 - NASA's twin Solar Terrestrial Relations
Observatories (Stereo A & B), which were launched in 2006, first
reached a point 180° apart from each other in their orbits
around the Sun, giving us the first 360° view of our star
ever. Contact was lost with Stereo B 3½ years later (10/1/14)
but was reestablished 22 months after that (8/21/16); a failed
inertial measurement unit makes it uncertain whether it will be
possible to resume science operations.
- Feb 6-8, 1946 - The largest sunspot group ever recorded
up to that time, covering ~1% of the surface of the Sun, created an
intense solar outburst at radio wavelengths which allowed Joseph L.
Pawsey and his group at the Radiophysics Laboraory in Australia,
working at 200 MHz, to deduce that the emitting region was 8-13
arc-minutes in size, showing that the radiation likely came from
the active regions and not from the sun as a whole.
Radar researchers during WWII had surmised that excess noise in
their systems was due to the Sun (or Milky Way), and only a few
months earlier they had shown that the radio noise from the Sun,
which varied by 30x over just a few weeks, correlated well with
the percentage of area on the Sun covered by spots.
- Feb 11/12, 1970 - Lambda 4S-5, first Japanese satellite
- Feb 14, 1990 - Voyager 2 takes the famous "pale blue
dot" photo, looking back at an Earth which only fills one pixel
at a distance of 40¼ AU, i.e., after flying by Neptune.
- Feb 16, 1948 - Uranus's moon Miranda is discovered by Gerard
Kuiper (see also Dec 7 &
- Feb 18, 1930 - Pluto is found by Clyde Tombaugh
(see above) during a search of plates taken
with the Lowell Observatory (Flagstaff) 13" telescope.
- Feb 20, 1962 - John Glenn aboard Friendship 7 orbits the
earth three times, first for an American.
- Feb 21, 1901 - Nova Persei (GK Persei) was first spotted
by the Scot Thomas Anderson. It reached the bright magnitude of 0.2,
or ½ magnitude brighter than Saturn. By the next year a small
expanding nebula surrounding it had been photographed at both the
Lick and Mount Wilson observatories with the new large telescopes
and photographic plates, which prompted speculation as to whether
the nebula was an expanding cloud or just a "light echo" hitting
material that had been expelled much earlier and was already in
place at the time of the explosion. After expanding for more than
a century it is now known as the Fireworks nebula.
- Feb 23, 1987 - SN1987a, the brightest supernova visible
from earth in 383 years, is discovered in the Large Magellanic Cloud
visually by Canadian Ian Shelton in Chile. (Hubble Space Telescope
- Feb 24, 1968 - The first pulsar was discovered, by Jocelyn
Bell, in a radio search survey. Hewish and Ryle, co-directors of the
project, got the 1974 Physics Nobel Prize for matching the observations
to a model of a rotating neutron star. This had first been explored
theoretically thirty years earlier by J. Robert Oppenheimer, who
in the interim became famous as the leader of the Los Alamos lab
which developed the A-bomb during WWII and, later, as the victim
of McCarthy era politics.
- Feb 26, 1979 - During an eclipse of the sun, Alan Clark
and Rita Boreiko use a NASA learjet to observe limb occultation of
the sun's chromosphere in the far infrared for the first time.
Yours truly's near-infrared (also called the "photographic infrared")
observation of the corona illuminated landscape 7 miles NNE of
Grassrange, Montana, during totality of the same eclipse, looking
generally W-WNW, so in the far distance at the left you can see the
area of sky outside the moon's shadow; this was a five second time
exposure on 4x5 Kodak High Speed Infrared film (#4143), and was a
crude but simple attempt to measure the integrated near-IR brightness
of the corona from the illumination level of the landscape:
©2002-2017, Chris Wetherill. All rights reserved. Display here does
NOT constitute or imply permission to copy, republish, or redistribute
my work in any manner for any purpose without prior written permission.
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