This Month in the History of Astronomy - October
- Oct 1, 1958 - NASA was established by an act of Congress.
- Oct 2, 1886 - Robert Trumpler, Swiss born and educated
astronomer who spent most his career in the U.S. studying galactic
star clusters (open clusters), discovered the interstellar absorption
of starlight by dust grains mixed in with the tenuous gas (independently
of Boris Vorontsov-Vel'laminov in Russia) in 1930, was involved in an
early test of Einstein's general theory of relativity (with Campbell
at Lick Observatory), and made observations of Mars which seriously
challenged Schiaparelli's claims about there being canals there;
Trumpler's proposal that the features may be volcanic faults found
support 50 years later with the Mariner 9 mission's return of the
first relatively close-up photos of the surface of the planet.
- Oct 5, 1882 - Robert Goddard, American rocketry pioneer.
- Oct 7, 1885 - Niels Bohr, Danish pioneer atomic physicist.
- Oct 8, 1873 - Ejnar Hertzsprung, Danish astronomer who
first proved the existence of giant and dwarf stars around 1910.
- Oct 9, 1873 - Karl Schwarzschild. Schwarzschild was the
first to solve Einstein's new general relativity field equations --
while serving in the German army in WW I in 1915, coming up with the
"Schwarzschild radius", the size of (the event horizon of) a black
hole. He died the next year of the autoimmune disease pemphigus,
which he contracted during the war. He's the father of equally
famous astrophysicist Martin Schwarzschild (see May 31).
- Oct 11, 1758 - Heinrich Olbers, German astronomer and
mathematician. Though chiefly remembered now for Olber's Paradox
in cosmology, he made important contributions at the time on comets,
asteroids, and the determination of their orbits.
At sixteen, Olbers calculated the time of a solar eclipse. Five years
later (1779) he determined an orbit for Bode's Comet using a process
first devised by Euclid. Before he was forty he discovered a new comet
(1796) and developed a new method to determine its orbit. Laplace had
also recently made advances in this area of celestial mechanics, and
Olbers extended the work; "Olber's method" achieved wide exposure when
it was used to re-determine the orbit of the 1779 comet, and was in
use throughout the nineteenth century.
Olber's expertise also came into play when the first asteroid (Ceres)
was discovered in the "gap" between Mars and Jupiter, then quickly
went behind the sun (superior conjunction), and was lost, since there
was no way to determine an orbit without making assumptions about its
eccentricity. Working with a young Karl Gauss, Olbers recovered the
object on the other side of the sun close to where Gauss had
calculated it to be. Olbers then went on to discover the second
asteroid, Pallas (1802), as well as Vesta (1807), the fourth (and
the second largest both by radius and mass, after Ceres).
In spite of these achievements Olber's main interest was in comets,
and he found four more, including one (1815) with a period close to
that of Halley's Comet, 72 vs. 76 years. He determined the orbits of
eighteen comets in all, and also came up with an early, simple model
for them consisting of a small, starlike nucleus surrounded by matter
expelled from it and repelled by the sun.
- Oct 13, 1933 - Founding of the British Interplanetary
- Oct 14, 1788 - Edward Sabine, British geophysicist and
astronomer who made extensive early investigations of earth's
magnetism and was the first, in 1851, to see the connection
between it and Samuel Schwabe's (see below) mass of data on solar
activity, linking magnetic storms on earth with the 10-11 year
sunspot cycle. Sabine was also the official astronomer on Sir John
Ross's 1818 expedition to find the Northwest Passage; the next year
he went with William Parry to the Arctic. He administered the King's
Observatory at Kew from 1849-71.
- Oct 15, 1829 - Asaph Hall, early U.S. astronomer who
discovered the two moons of Mars, first measured the rotation rate
of Saturn, and became known as "the caretaker of the (planets')
satellites". He also worked on Uranus and Neptune, stellar parallax
measurements and double stars, as well as the Pleiades star cluster.
Hall started out at the Harvard observatory in 1856 and quickly showed
his expertise in both observing and orbit calculation. His skill in
computing numbers for astronomical almanacs earned him a transfer
promotion (1862) to become an assistant astronomer at the U.S. Naval
Observatory under Simon Newcomb, where he was promoted to a
professorship a year later, a post he held until retirement thirty
years later, though he stayed on as a volunteer observer until 1898.
He then spent five years back at Harvard teaching celestial mechanics,
was president of the American Association for the Advancement of
Science (1902), and an associate editor for the then new Astronomical
Journal from 1897 until his death ten years later.
In 1875 Hall was put in charge of the USNO's new (1873) 26" Clark
refractor, the largest and probably best telescope in the world for
at least the next decade. His first discovery came quickly as a result
of the superior technology, and was of a white spot on Saturn, which
he used to determine Saturn's rotation rate.
Two years later Mars was at a close opposition and his discovery of
Deimos came on Aug 11. After six days (4+ orbital periods) he was
convinced it was a Martian moon, and on this same night (the 17th)
he discovered Phobos -- which is ~1¼ magnitudes brighter but
very close to the planet. He had previously done the calculations
to show that Mars could have satellites only if they were close to
the planet, so he knew where to look (and where not to). Phobos is
at magnitude 11.6 and orbits at only 9,375 km from the center of
Mars (itself 3400 km in radius) in less than 8 hours. Deimos is
2½x further out. The moons allowed Mars's mass and density
to be calculated rather than guesstimated for the first time.
In 1884 he showed Saturn's moon Hyperion had an orbit that was
retrograding -- the whole orbit was rotating in space "backwards"
-- at the rate of 20° per year.
- Oct 15, 1909 - Jesse Greenstein, U.S. astronomer probably
most remembered for his involvement in the discovery of quasars.
Greenstein did his Ph.D. thesis an interstellar dust at Harvard
(1937) and spent about a decade at the Yerkes Observatory before
moving to Cal Tech and the Mount Wilson & Palomar Observatories
in 1948, which he (formally) retired from in 1980.
His early work, motivated by unusual stellar spectra, was on
stellar atmospheres and abundances. This led to his development
of theories of stellar interiors which required neutron-producing
nuclear reactions to be present in red giant stars, to account
for the creation of the heavier elements observed.
He next turned to the problem of interestellar dust again, and
showed that the interstellar polarization of starlight could be
explained by there being spinning grains aligned by a galactic
magnetic field; elements like iron in at least some of the grains
would be required to make them magnetic, while they'd have to be
aspherical (longer than they are wide) in order to produce the
polarization, which is rarely more than 1%. This is still a
valuable basic method for mapping the galaxy's global magnetic
Greenstein got involved early on in the optical identification
of the mysterious objects being turned up by the dozen by the
3rd Cambridge radio all-sky survey. The radio coordinates were
very imprecise, but some of the objects were in the zone of sky
traversed by the moon, and an occultation allowed the location
to be restricted to an arc along the limb of the moon at the
instant the source 'blinked' off (or on) -- a vast improvement.
Spectra were then taken of the remaining candidates to try and
find anything out of the ordinary. 3C 273, by Marteen Schmidt,
and then Greenstein's 3C 48 were found in quick succession and
determined to have extraordinary recession velocities (1964).
By Hubble's Law these had to be at large distances, and were
extremely luminous (100x that of a galaxy) in order to be as
bright as observed at such distances. Quasars were an entirely
new and unexpected class of objects. This was the first really
big, astounding discovery made by the 200" telescope, and it
also secured the importance of radio astronomy as an indispensible
tool for exploring the universe.
Quasars having blue colors, Greenstein in the 1970's got involved
in optical searches for faint blue objects. While turning up
radio quiet quasars, he also found over 500 white dwarf
stars. This led him back to further developments in the late
stages of stellar evolution and the course a star takes from
red giant to becoming a white dwarf.
Greenstein was also involved in the 1970's in the part of SETI
(the Search for ExtraTerrestial
Intelligence) relating to
the search for extra-solar planets.
- Oct 15, 1949 - Thomas Bopp, co-discoverer (within
5 minutes) with Alan Hale, of Comet C/1995 O1 on July 22, 1995,
which reached magnitude -1 near its perihelion nearly two years
later (April 1, 1997). One of the brightest comets of the century,
Comet Hale-Bopp was said to have been seen by two-thirds of all
- Oct 22, 1905 - Karl Jansky, American physicist and
electrical engineer, who discovered the first extraterrestrial
radio waves (at 20.5 MHz) in the course of investigating noise
and interference in ship-to-shore communications systems for
Bell Labs in 1931-32.
Using a high quality receiver and a movable aerial antenna (mounted
on wheels), he was able to determine the radiation was coming from
the direction of Sagittarius, which astronomers Harlow Shapley and
Jan Oort had recently identified as being the direction to the
center of the Milky Way Galaxy.
Even though the discovery was front-page news, until after WW II
it was only followed up by amateur Grote Reber, using homemade
radio equipment and a fixed, zenith pointing, backyard "dish"
made of lumber yard wood.
- Oct 23, 4004 B.C. - The date of Creation, as erroneously
determined in about 1640 by archbishop James Ussher. Astronomers
tend to use Julian Day Numbers (and decimal fractions thereof),
which start Jan 1, 4713 B.C.. As no known astronomical record
precedes this date, JDN's are always positive; they also 'flip
over' at noon (Greenwich time), so nightime observations are not
split between two days.
- Oct 25, 1789 - Samuel Schwabe, German chemist and
pharmicist turned astronomer who observed sunspots daily his
entire life, starting in 1825, with a 2" telescope, and by
1843 had accumulated enough data to determine a periodicity
in solar activity -- the sunspot cycle -- of ten years. His
publication went unnoticed until 1851, when it was mentioned
in a book by famed explorer and naturalist Alexander von
Humboldt. This prompted several others with sunspot data to
analyze it similarly, the length of the cycle was increased
to 11.1 years, and not long after the connection with magnetic
storms on earth was shown. Schwabe also made the first known
drawing of Jupiter showing the Great Red Spot, in 1831.
- Oct 25, 1877 - Henry Norris Russell, American pioneer
in establishing the modern field of astrophysics. The namesake for
the American Astronomical Society's highest award (for a lifetime
contribution to the field), Russell is the "R" in "H-R diagram",
which he first used in a 1914 paper. (Ejnar Hertzsprung,
see above, is the "H".)
- Oct, 1785 (exact date unknown) - James South,
British astronomer who worked with John Herschel on double
stars, publishing a prize- and award-winning catalog (with
charts) on 380 of them in 1824.
Discoveries and other firsts
- Oct 1, 1897 - Dedication of the University of Chicago's
Yerkes Observatory with its 40" refractor, still the world's
largest such telescope.
- Oct 1, 1962 - The 300-foot radio telescope of the
National Radio Astronomy Observatory (NRAO) goes into operation
at Green Bank, West Virginia. The telescope, which collapsed
suddenly on Nov. 15, 1988, was the world's 2nd largest.
- Oct 4, 1957 - The USSR's Sputnik 1 becomes the first
manmade object to orbit the earth.
- Oct 5, 1923 - Edwin Hubble discovers the first Cepheid
variable in M31, the Andromeda Galaxy, establishing that spiral
nebulae are independent and external stellar systems like the
- Oct 7, 1959 - The USSR's Luna 3 returns the first photos
of the Moon's far side.
- Oct 10, 1846 - William Lassell discovers Neptune's
moon Triton, just seventeen days after the discovery of the
- Oct 12, 1957 - Britain's Jodrell Bank radio observatory
radar detects the Russian R-7 rocket booster that put Sputnik into
orbit, the final stage having gone into orbit along with its satellite
payload. Only in operation for a few months (barely), Jodrell Bank was
then the only facility on earth capable of doing this. Ten weeks later
Moscow sent them a telegram of thanks and wishes for "every success in
your work". Jodrell Bank continued to track both early earth satellites
and at least one spacecraft sent to the moon, for several countries,
before dedicated networks for doing this were built.
- Oct 12, 2017 - A small space rock designated 2012
TC4 becomes the first known asteroid to pass by earth
closer than the Earth-Moon distance twice. It was discovered
five years earlier (Oct 4), just eight days before its first closest
approach of 94,960 km. Orbital extrapolations at the time suggested
it would come back around at under three Earth radii next time by.
The object was picked up a second time, at the incredibly faint
magnitude of 27, by the ESO's VLT (Very Large Telescope) on July 27
at a distance of 0.4 AU. The 10/12/17 pass of the 15 meter sized
rock was at only 50,150 km, ~1/8th the Earth-Moon distance, and
not far beyond the distance of geosynchronous satellites. The next
close pass for 2012 TC4 is now estimated to be on
December 1, 2079, at a distance about 1 million km.
- Oct 15, 1963 - The first detection of an interstellar
molecule (OH), by Sander Weinreb (w/Barret, Meeks, and Henry) on
the MIT Millstone Hill 84-foot dish. The detection of the hydroxyl
molecule (OH) in absorption, using the radio galaxy Cas A as a
background continuum source, was made possible by new correlation
receiver technology and occurred at 1667.46 MHz and, shortly
later, 1665.34 MHz. By the turn of the millennium, approximately
200 different molecules -- many of them organic -- had been
discovered in interstellar space.
- Oct 15, 1997 - Launch of the Cassini spacecraft to
Saturn and its moon Titan.
- Oct 12, 1892 - E. E. Barnard is the first to discover
a comet (1892 V) by means of a photograph. (But see
- Oct 16, 1982 - Halley's Comet's approach for its 1986
apparition was first detected by U.S. astronomers David Jewitt
and G. Edward Danielson using the 5.1 m Hale telescope at Mount
Palomar and a CCD camera. Solid state, CCD technology was extremely
new then, very expensive, and required a "CCD Doctor" (or two or
three) to make and keep it working, so this was one of its first
- Oct 18, 1967 - First spacecraft probe of Venus's
atmosphere, by the USSR's Venera 4.
- Oct 19, 1899 - A seventeen-year-old Robert H. Goddard,
while climbing a cherry tree, first envisions a vehicle capable of
taking humans to other planets and resolves to devote himself to
the task of making it happen -- an early moment the rocket pioneer
recollected and remembered the date of the rest of his life.
- Oct 22, 2136 B.C. - The first recorded solar
eclipse is witnessed by Chinese astronomers. Eclipse prediction
was probably already a fairly well developed science at this time
because royal astronomers Hsi and Ho were executed by an unhappy
emperor for their failure to predict the eclipse.
- Oct 22, 1975 - Venera 9 sends back the first photos
from Venus's surface.
- Oct 24, 1851 - William Lassell discovers Uranus's moons
Ariel and Umbriel.
- Oct 24, 1931 - The first mention in print of using radio
waves for interstellar communication with civilizations on other
planets, by E.W. (Ernest William) Barnes.
Speaking of these other possible planetary systems, "...If even one
such system were found, the present theory of planetary origins would
collapse [see below]. Failing any such invention of a super-telescope,
there remains the possibility of wireless communication. As I have
already indicated, I have no doubt that there are many other inhabited
worlds, and that on some of them beings exist who are immeasurably
beyond out mental level. We should be rash to deny that they can use
radiation so penetrating as to convey messages to earth. Probably such
messages now come. When they are first made intelligible a new era in
the history of humanity will begin. At the beginning of the era the
opposition between those who welcome the new knowledge and those who
deem it dangerously subversive will doubtless lead to world war."
(Nature, vol 128, pgs 722-24)
Since there are already enough reasons for world war, I suppose this
explains why the status quo, the Establishment, Dave Barry's "The
Committee That Really Runs America", or whatever you call it, has
pretty effectively scotched SETI without being too overt by the
outright banning of it.
The now out-dated and mostly forgotten theory of planetary origins
mentioned relied on a catastrophe, where the gravity of a star passing
very close by the sun drew out material from either (or both) stars
which subsequently condensed into the solar system. In the life of
the galaxy out where the sun orbits, the statistical expectation
would be that such near-collisions only ever happen once or twice
(or not at all). This would make the origin of the solar system a
virtually singular event, though the observational data to calculate
the total galaxy lifetime stellar collision cross-section didn't
exist back then. So they didn't know stars don't ever collide (or
even almost collide), and no examples have yet been turned up. This
is fundamentally because the stars in the disk all orbit the galaxy
in near-circular orbits with random velocity deviations on the order
of only ~5% or less: maybe ±10 km/sec, compared to an orbital
velocity 225-250 km/sec. Even if the 'impact parameter' was ideal
it's still no certainty a solar system would result.
The article finishes... "But the survivors, when they extricate
themselves from the economic consequences of the peace treaty, will
begin what we may correctly term a strenuous correspondence course.
I should like to be living then. We might get a true understanding
of the evolution of universe."
- Oct 25, 1671 - Giovanni Cassini discovers Saturn's moon
- Oct 25, 2017 - Japanese astronomer Tadashi Kojima becomes
the first amateur to discover an exo-planet. While hunting for novae
in Taurus, Kojima found a star whose brightening fit the pattern
expected for a gravitational microlensing event, where two stars
are almost perfectly in line with earth and the gravity of the nearer
one lenses (or magnifies) the light of the more distant star. The
presence of the planet, ~20% more massive than Neptune and roughly
1 AU from its host star, could be deduced from its varying effect
on the brightening of the background star, as the planet's orbital
motion causes its small contribution to the lensing gravity to
vary with time.
- Oct 27, 1577 - The date of perihelion passage of the Great
Comet of 1577 (aka C/1577 V1). The first recorded observation was
Nov 1, in Peru, and the first European observation, in Italy, came
Tycho Brahe first observed the comet on Nov 13th, and observed it
until Jan 26, 1578. By comparing his position for the comet on the
sky with other's positions, especially those of Thadaeus Hagecius
in Prague, Brahe was able to use parallax to show that the comet
was further away than the moon -- maybe 3x further -- i.e., it was
not an atmospheric phenomenon.
Twenty-two years later, after being exiled from Denmark to Prague,
Brahe employed Kepler as his assistant, and after Brahe died 3-4
years later Kepler inherited his observations and was eventually
able to determine the comet's orbit. That it had traversed the
orbit of Venus, a proposal made earlier by the distance estimates
of Michael Maestlin (Kepler's former teacher), before Brahe had
died, seemed to be the death knell for the idea of celestial
spheres, transparent crystalline spheres made of an unknown
material ("quintessence") hypothesized to exist for the sole
purpose of carrying the planets around on their orbits, because
the comet would have had to crash right through them according to
the observations. Nevertheless, the idea held on until later in
the seventeenth century, when Newton developed his principles of
gravity and motion, from which Kepler's three empirical laws of
planetary orbital motion could be derived.
- Oct 28, 1971 - Great Britain launches its 1st satellite.
- Oct 29, 1749 - M32, a satellite galaxy of the Andromeda
Galaxy (M31), is the first such dwarf galaxy discovered, by the
French astronomer Le Gentil using an 18 ft focal length telescope.
He described it as a "nebula about one minute [of arc] in diameter
which appeared to throw out two small rays; one to the right and
the other to the left". It would be almost another 175 years before
M31 and M32 were recognized by Hubble as galaxies (see Oct 5th above).
©2002-2019, 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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