This Month in the History of Astronomy - April
- Apr 2, 1889 - Harvard Observatory's 13" refractor arrives
on Mount Wilson, a month later beginning a long astronomical legacy
at this site which housed the largest telescopes in the world from
1908-48: the 60" for the first decade followed by the 100". This
latter mirror is still the largest solid ever cast in plate glass;
weighing 4 1/2 tons it's just 13 inches thick. Subsequent large
mirrors were cast in borosilicate glass (pyrex) so they wouldn't
change shape so much as the temperature changed during a night;
the larger mirrors also evolved in the direction of being made
lighter (and stiffer) by removing some (or most) of the inside
glass on the underside of the mirror, making it more a structured
object rather than just a big disk of glass.
- Apr 3, 1842 - Hermann Vogel, the first to discover
spectroscopic binary stars (Algol and Spica), where an unseen
companion star can be deduced from the periodic Doppler shifts
in the spectral lines of the observable, brighter component. (In
the case of Algol the companion was already known to be there
because it is an eclipsing binary. At radio wavelengths the Sun
is a member of a sort of spectroscopic binary system as seen by
an outside observer, with the earth the brighter componenet, due
to our TV and military radar emissions.
The study of spectroscopic binary stars led Vogel to the further
discovery of interstellar calcium absorption lines, which are
stationary in the spectrum, part of the gradual realization that
insterstellar space is not a perfect vacuum and is not therefore
perfectly transparent. Vogel was also the first to study the
evolution of the specturm of a nova. He spent the bulk of his
career at the Potsdam Astrophysical Observatory near Berlin.
- Apr 5, 1935 - Donald Lynden-Bell, British theoretical
astrophysicist who spent his career at Cambridge. He was the first
to suggest there were supermassive black holes at the centers of
galaxies, that quasars were powered by black holes accreting
material, and that the nucleii of local, current-day galaxies
were collapsed, old ("dead") quasars (1969).
His 1960 Ph.D. thesis was on "Stellar and Galactic Dynamics", a
field he continued to contribute to through development of such
concepts as "violent relaxation" and "gravothermal catastrophe"
(cluster core collapse).
Besides becoming director of the Institute of Astronomy, Lynden-Bell
won about every major award astronomy has to offer, including the
Gold Medal of the Royal Astronomical Society, the American
Astronomical Society's Henry Norris Russell Lectureship, the
Karl Schwarzschild and Eddington Medals, as well as the Bruce Medal
of the Astronomical Society of the Pacific.
- Apr 7, 1991 - The Gamma Ray Observatory (GRO) was
deployed.
- Apr 8, 2009 - First light for the Kepler spacecraft,
a 0.95 meter Schmidt telescope with 42 CCD detectors at its focal
plane.
- Apr 11, 1862 - William Wallace Campbell, pioneer
observer of stellar motions and radial velocities, and director
of Lick Observatory from 1901 to 1930. He was president of the
University of California and the National Academy of Sciences,
and the building on the UC/Berkeley campus housing the astronomy
department is named after him. In 1919 Campbell was involved in
the highly publicized observations of a total solar eclipse
looking for the deflections of starlight predicted by Einstein's
General Relativity. (see May 29)
- Apr 11, 1901 - Donald H. Menzel, born in Florence,
Colorado, and raised in Leadville, he was a Ph.D. student of
Henry Norris Russell and had a long and distinguished career,
part of it as the director of the Harvard College Observatory.
- Apr 14, 1629 - Christian Huygens, Dutch scientist and
one of the preeminent scientists of the 17th century. Besides
developing a theory of light and getting the first patent for a
pendulum clock, Huygens was the first to discern Saturn's rings
and he also discovered Saturn's largest satellite, Titan. (See
the 25th of last month.)
- Apr 15, 1707 - Leonard Euler, famed Swiss
mathematician who lost the sight of his right eye while
observing the sun (1733-4).
Euler studied under Jean Bernoulli in Basle, earning his master's
degree at age sixteen. He had positions in both St. Petersburg,
Russia (Naval College, Academy of Sciences), and Berlin, Germany
(Academy of Sciences); he knew both Frederick the Great (Germany)
and Empress Catherine the Great (Russia).
Euler made advances in celestial mechanics, and the inclusion of
tidal forces in analyzing the earth-moon-system for the first time,
but is perhaps best known for having the base of natural logarithms,
the transcendental number "e" (2.71828...), named/abbreviated after
him.
He was also responsible for practically inventing spherical
trigonometry, for bringing integral and differential calculus
close to their modern forms, and for standardizing notation by
consisently using symbols like π, i (imaginary/complex
numbers), and Σ (summation).
- Apr 22, 1724 - Immanuel Kant, German philosopher whose
contributions ranged into the natural sciences and astronoly.
Kant's paternal grandfather was a Scottish immigrant who had germanized
their last name from Cant, according to Kant, though later scholars
dispute this.
At barely the age of thirty Kant developed Newton's mathematical physics
to show how the moon's tidal interaction with the earth would slow down
the earth's spin and eventually lead to the moon's synchronous rotation
with the earth. The next year he published Universal Natural History
and Theory of the Heavens, in which he laid out his "nebular
hypothesis" for the formation of the solar system from a giant spinning
gas cloud. This would naturally explain why all the planets orbit in
roughly the same plane and in the same direction. Kant further speculated
that the Milky Way was a giant spinning disk of stars that had also
formed out of a gas cloud, an even larger gas cloud, and that the faint
"nebulae" then being turned up in the largest telescopes of the day were
examples of the same thing, which turned out to be correct even though
it wouldn't be soundly established for almost another 175 years. Kant
also went on to work on the theory of the winds (the Coriolis force)
and was a big advocate for the nascent fields of both geography and
geology.
- Apr 22, 1891 - Sir Harold Jeffreys, astrogeophysicist and
the first to hypothesize the Earth's liquid core; Jeffreys also made
contributions to our understanding of tidal friction, nutation,
general planetary structure, and the origin of the solar system.
- Apr 23, 1858 - Max Planck, pioneer quantum physicist.
The Planck equation describes the amount of light energy emitted
by a "blackbody" as a function of the its temperature (on an absolute
scale) and the wavelength (or frequency) of emission. Blackbodies
are perfect absorbers of light and approximate stars over a wide
range of conditions. Other astronomical objects also radiate like
blackbodies over some or all parts of the spectrum, a notable
example being nebulae such as the Orion Nebula in the radio part
of the spectrum, where the temperature properly refers to that of
the electrons involved in the flourescence process which makes the
visible light we see.
- Apr 25, 1923 - Francis Graham Smith, pioneer British
radioastronomer who was also Director of the Royal Greenwich
Observatory during the development of Las Palmas Observatory in
the Canary Islands, which includes both optical and radio facilities.
His early investigations with Martin Ryle and his radio interferometer
were of the Sun, but the techniques developed and the expertise gained
led to the discovery and identification of both Cygnus A (a Type II
supernova remnant) and Cassiopeia A (a double lobed radio galaxy).
Smith was also involved in the systematic radio sky survey that led to
the 3C catalog (the 3rd Cambridge radio source catalog)
in 1959; the first quasar, 3C 273, was turned up a few years later
(1963) while characterizing the contents of the catalog.
Smith was also involved, again along with Ryle, in early studies of
the use of artificial satellites for navigational purposes (1957).
At the Jodrell Bank radio facility from 1964 to 1974, Smith mainly
studied pulsars, being the first to show their radiation is strongly
polarized, which led to his development of the 'relativistic beaming'
mechanism or model for pulsar radiation (1970). He also made some
of the first measures of the magnitude of interstellar magnetic
fields in the Milky Way, again using polarization as way to
determine the amount of alignment of interstellar dust grains
containing iron with the field.
- Apr 26, 1933 - Arno Penzias, Nobel Prize winner for his
part in the discovery of the cosmic microwave background radiation.
- Apr 28, 1774 - Francis Baily, a British explorer and
stockbroker until turning to astronomy at the age of 50. Baily
helped found the Royal Astronomical Society of London, revised
star catalogs, and studied meteorology. He's most remembered for
his observations of the May 15, 1836 solar eclipse, an annular
eclipse visible in Scotland, and his explanation of the phenomenon
at the beginning and ending of totality, now known as Baily's
Beads.
- Apr 28, 1900 - Jan Hendrick Oort, Dutch astronomer who
first quantified the Milky Way's rotation characteristics (via
Oort's Constants) and proposed a vast, spherical resevoir of comets
(the Oort Cloud) surrounding the Sun and stretching nearly half way
to the nearest stars. One of the foremost astronomers of the 20th
cntury, Oort was a pioneer in radio astronomy and the 21 cm mapping
of the galaxy, as well as a driving force behind the creation of
the European Southern Obsrvatory.
- Apr 28, 1906 - Bart Jan Bok, Dutch-born American astronomer
who had a distinguished career studying the structure and dynamics of
the Milky Way, and who, with his astronomer/wife Priscilla, authored
a classic book on the subject. As director of the Univ. of Arizona's
Steward Obs., Bok was also influential in the siting of Kitt Peak
National Observatory in the Tucson area.
- April 28, 1928 - Gene Shoemaker, American geologist
turned astro-geophysicist, who was central in the development of
the new field of planetary sciences.
Raised in Los Angeles, Shoemaker enrolled in high school at age
thirteen and graduated in just three years. Entering Cal Tech, he
got his bachelor's degree before turning twenty (1948), and his
M.Sc. degree, also from Cal Tech, the next year.
He would then go to work for the U.S. Geological Survey, searching
for uranium deposits in Utah and Colorado, which had been found to
be associated with volcanic vents. This led him to Meteor Crater in
NE Arizona, at that time accepted as a volcanic crater -- though its
discoverer (1891), Daniel Barringer, had thought it formed from a
meteor impact. Shoemaker's investigations used the shapes of craters
formed by atomic bomb tests in Nevada to show Meteor Crater was
created explosively, the case being sealed in 1960 (the year he got
his Ph.D. from Princeton) by his discovery there, with Edward Chao,
of shocked quartz. Fragments of clearly meteoritic/asteroidal
origin were also found.
In the 1960's, Shoemaker turned to the moon, creating its first
geologic map, using telescope photos made by Francis Pease, and
then worked with Urey and Kuiper on the Lunar Ranger imaging
program, which was preparatory to the Apollo moon landings, as
were the Lunar Surveyor missions, where he led the imaging team.
Shoemaker then became the lunar geology principal investigator
for Apollo's 11 thru 13. He became well-known for his appearances
with Walter Cronkite as an affable and moustachioed lunar geology
TV expert during coverage of the early Apollo missions.
While continuing as a consultant with NASA the rest of his life,
Shoemaker joined Cal Tech in 1969 and began the search for
earth-crossing asteroids. He would go on to be involved in the
discovery of 820 asteroids and comets, including several families
of earth-crossers -- the Apollo asteroids among them. Shoemaker,
along with his wife Carolyn, made extensive use of the 18" Schmidt
telescope built by Fritz Zwicky in
the 1930s, which is now in the Vistor's Center at Mount Palomar.
Comet Shoemaker2–Levy 9 had already been captured by
Jupiter's gravity and tidally disrupted into more than a dozen
fragments when it was discovered in 1993; it was quickly realized
that its orbit would cause the pieces to impact Jupiter, which it
did spectacularly in July of the next year.
Shoemaker was unfortunately killed in an auto accident three years
later while searching remote Australia for impact craters. In 1999
the Lunar Prospector spacecraft carried his ashes to the moon.
[Photo at right: Gene Shoemaker tries on a Bell Aerosystems
"rocket belt" in 1966 outside Flagstaff, at the US Geological
Survey's lunar surface simulation landscape test area. NASA at
that time was considering using such devices (LFUs = Lunar Flying
Units) to enable the astronauts sufficient mobility to explore the
moon better, but later decided it would just be too awkward and
dangerous with the big, heavy, stiff spacesuits they had to wear
-- in favor of the lunar rover vehicle (LRV, aka the moon dune
buggy) used on the last three Apollo missions. Shoemaker never
fired the unit up or flew anywhere with it.]
- Apr 30, 1777 - Karl Gauss, German mathematician, physicist,
and astronomer. Something of a precocious talent, Gauss was only fourteen
when he so impressed the Duke of Brunswick that the latter supported
him generously for the next fifteen years. By twenty-two he had earned
his doctorate, and was both professor of mathematics and director of
the Göttingen Observatory by age thirty, where he remained the
rest of his working life of nearly five decades, despite offers from
several foreign math/science powerhouse countries of the time.
During his teen years he developed the principle of least squares,
and, as a founder of what would later be called number theory, Gauss
did the first work on the frequency of prime numbers. By his early
twenties he had made the first discovery in Euclidean geometry in
2,000 years -- that a 17-sided polygon could be inscribed within a
circle using only a ruler and compass -- and had also proved a
fundamental theorem of algebra, that every equation has a complex
(or imaginary) root, and that such numbers can be described
analogously to points in a plane.
He next turned to astronomy for about the next decade. Inspired by
the discovery (1801) and subsequent 'loss' of the first asteroid,
Ceres, as it passed on the far side of its orbit behind the sun, he
developed the now classic method for determining an object's six
orbital elements from three observations, which he published in
1809.
He then extended this work into the basic theory of orbital
"perturbations", which Leverrier and Adams used several decades
later to analyze the motion of Uranus and correctly deduce the
existence and location on the sky of Neptune (1846).
In his fifties, Gauss got involved in the study of crystallography,
optics, mechanics, and capillary action. He worked with Wilhelm Weber
on electricity and magnetism, and the two invented the first telegraph
(1833). The unit of magnetic flux density (magnetic field strength) is
known as the Gauss in honor of this pioneering research, while Weber
has another unit named after him. (The first use of the letter "c"
-- for "celeritas", meaning "fast" -- for the speed of light was in
an 1856 paper by Kohlrausch and Weber.)
Discoveries and other firsts
- Apr 1, 1960 - First weather satellite, Tiros 1, launched.
- Apr 1, 1998 - NASA's TRACE (Transition Region and Coronal
Explorer) satellite is launched, providing the first high-resolution
observations of the sun from space.
- Apr 2, 1845 - First photo of the Sun taken.
- Apr 3, 33 - the date of a partial lunar eclipse rising
over Jerusalem, which biblical scholars Humphreys and Waddington
(1983) concluded was the most likely date for the crucifixion of
Jesus.
- Apr 3, 1966 - First lunar orbiter, Luna 10.
- Apr 7, 1959 - Astronomers at the Ondrejov Observatory, in
what was then Czechoslovakia, photograph the Pribram meteorite fall
with multiple special cameras, equipped to take time exposures but
also with a shutter so that any meteor track would be recorded as
a series of dashes. This allowed the speed of the meteor to be
determined. The multiple cameras made it possible to triangulate
on the meteor and reconstruct its 3-D track through the atmosphere.
This both allowed a projection towards the ground, where within a
week 5.8 kg of the meteorite was recovered, as well as a projection
backward to determine the meteoroid's orbit before encountering the
earth. All these were firsts for any meteor.
- April 10, 531 - One of the most spectacular meteor showers
of the first millennium, lasting about two hours, and due to a series
of close approaches to earth by Halley's Comet at its most recent three
apparitions -- in 295, 374, and 451 -- the April 1, 374, passage being
the second closest known. The earliest known record of the Eta Aquariid
meteor shower was made in 74 B.C. by Chinese astronomers, and there is
evidence from Mayan records that they used the timing of this shower to
determine the length of what we'd call the sidereal year.
- Apr 10, 2019 - The Event Horizon Telescope (EHT) project,
consisting of a collaboration of 200+ scientists at radio observatories
around the world with millimeter wavelength capabilities, releases the
first ever image of a blackhole -- the super-massive blackhole at the
center of the giant elliptical galaxy M87 in the Virgo Cluster. See
the book Einstein's Shadow (Seth Fletcher, 2018) for full
details on this latest application of Very Long Baseline Interferometry
(VLBI) at very short wavelengths.
- Apr 11, 1960 - First radio search for extraterrestrial
civilizations, started by Frank Drake (Project Ozma).
- Apr 11, 1986 - At 65 million km (0.43 AU), Halley's Comet
is closest to Earth for this apparition.
- Apr 12, 1961 - First man in space, Yuri Gagarin, makes
one orbit aboard Vostok 1.
- Apr 12, 1981 - First Space Shuttle (Columbia) launch.
- Apr 14, 1969 - Nimbus 3 was launched, the first weather
satellite with an infrared spectrometer to measure earth's atmospheric
composition and temperature profile. In all there were seven Nimbus
earth observing platforms launched over a fourteen year period
(1964-78), and Nimbus 3 was the first to test a radioisotope
thermoelectric power generator; these kinds of power units were
subsequently used on many missions to the outer planets, where
sunlight is so dim that solar panels are impractical.
- April 16, 2019 - Abraham Loeb and Amir Siraj at
Harvard report the discovery of the first meteor of interstellar
origin, based on a back-tracking of its well-observed
trajectory.
- Apr 17, 1912 - The unusual hybrid eclipse of the sun
just two days after the sinking of the Titanic in the nearly new
moon North Atlantic.
A hybrid eclipse is a combination annular and total solar eclipse,
where the moon and sun are almost exactly equal in angular size, so
that the difference in the distance to the moon from different places
on the curved surface of the earth can swing the eclipse one way or
the other. Such eclipses start and end annularly, with a period of
totality centered on the eclipse midpoint, which experiences the
eclipse at local sundial noon and so is at the center of the region
on earth closest to the moon (so it appears slightly bigger).
For this eclipse, which was about as close to not being a hybrid
eclipse as it's possible to be, the brief period of totality (only
2 seconds max, and but 1 km wide) occured in Spain and Portugal.
The beginning of the period of slight annularity passed just to the
NW of Paris -- it's first eclipse of such a magnitude in 188 years
-- before continuing NE through northern Europe and NW Russia. The
other end of the annular eclipse touched the region in N South
America where Venezuela and Brazil meet before heading out across
the ocean towards Europe.
This Saros (#137) had one more hybrid eclipse in it (1930). All
eclipses in the cycle subsequently have been and will be annular,
including the one on the Summer Solstice in 2020 -- until the 26th
century, when they will become only partial.
- April 18, 2019 - The first molecule thought to have
formed in the early universe, helium hydride (HeH+),
is announced in Nature to have been found out in the
current universe by Rolf Güsten and collegues at the Max
Planck Institute for Astronomy, using NASA's Stratospheric
Observatory for Infrared Astronomy (SOFIA - a modified Boeing
747) to observe the planetary nebula NGC 7027 at a sub-millimeter,
far IR wavelength of 149.137 microns (2,011.57 GHz).
Helium was practically the only element besides hydrogen to have
formed in big bang cosmologies, and it has the highest ionization
potential for any (neutral) atom, 24.6 eV. This corresponds to
a hard-UV wavelength of light of 508.4Å (or less), which
is only emitted in appreciable quantities by the very hottest
objects (~100,000+°K), like the central stars of the youngest
planetary nebulae -- or the universe at an age of several hundred
years old.
The molecule is fragile and easily reacts in a cosmic environment
with abundant hydrogen to liberate the helium atom and form an
H2 molecule, this second reaction becoming dominant
when the helium hydride production rate falls off as the
temperature declines. This unusual molecule was first synthesized
on earth in the laboratory in 1925.
- Apr 21, 1972 -- First telescope on the moon, by Apollo 16
astronauts John W. Young and Charles M. Duke Jr.
- Apr 22, 1715 - The first total solar eclipse predicted
well enough and far enough in advance (by Edmond Halley) that
someone -- Monsieur le Chevalier de Louville, of the Royal Academy
of Sciences in Paris -- could travel in advance to observe it, in
this case to London, which hadn't been in the path of totality for
575 years.
- Apr 24, 1970 - China launches its first satellite.
- Apr 24, 2014 - NASA and Kevin Luhman, an astronomer at
Pennsylvania State University's Center for Exoplanets and Habitable
Worlds, announce the discovery of WISE J085510.83-071442.5, the
coolest sub-brown dwarf yet found, at about 250°K, at a
distance of only 2 parsecs. Considered by some to be a rogue
planet because it's mass is only a few times Jupiter's (3x-10x),
the object is so close to earth that it's proper motion across the
sky, of 8.1 arc-seconds per year, is third only to Barnard's Star
and Kapteyn's Star. It displaces Wolf 359 as the fourth closest
system. Luhman actually first picked up the object's fast motion
in WISE (Wide-field Infrared Survey
Explorer ) data in March of 2013, but then spent a
year with the Spitzer Space Telescope and ground-based
observations to better characterize its extraordinary nature.
- Apr 25, 1990 - The Hubble Space Telescope is deployed
from the space shuttle Challenger, having been launched the day
before.
- Apr 25, 1998 - The first time a gamma-ray burst (GRB
980425) is observationally connected both in direction and time
with a supernova explosion (SN 1998bw). The GRB was found with
the Compton Gamma Ray Observatory and was of the "long-soft"
variety; these have a median burst duration of ~20 seconds and
a peak energy at a photon energy of ~220 keV, which is almost
half the rest-mass energy of an electron. The SN had a distinctive
and/or unusual Type Ic spectrum, meaning it showed no hydrogen
(H I) lines and lacked either strong helium (He I) or ionized
silicon (Si II) lines. It was also the most luminous radio SN
discovered up to that time, peaking ~50-60 days after exploding,
whereas regular SN only produce energy at radio wavelengths much
later in their evolution.
The event occurred in the galaxy ESO 184-G82 and the SN was
at magnitude 15.7. At z=0.0085, the GRB was thus closer by a
factor of 100 than any other optically identified GRB.
A possible second GRB+SN event was then found, after it had
happened, in archival data of GRB 970514 and SN 1997cy. The
SN, discovered July 1997, had an uncertain date for its explosion,
but was probably more than a month old when found. The GRB in
this instance was of the "short-hard" variety with a duration
of only ~0.2 seconds and energy above 300 keV, making it the
only GRB of this sort with an identified optical counterpart.
Several more subsequent similar events have led astronomers to
think the progenitor stars might be core-collapse Wolf-Rayet
stars that have lost most or all of their hydrogen envelopes
through strong stellar winds, exposing what were once their
helium cores. SN 1997cy showed hydrogen lines (with both broad
and narrow H-alpha emission components, thought to originate
in the circumstellar gas) and is thus formally of Type II, but
was reminiscent in some ways of the peculiar Type IIn SN 1988Z,
or of SN 1999E, but was unique when its spectrum and light
curve were taken together.
- Apr 26, 1759 - The first predicted return of Halley's Comet.
On this date it made its closest approach to earth in nearly 400 years,
at a little more than 11 million miles, 44 days after perihelion.
Halley made his prediction in 1705, but would die in 1742, and 'his'
comet would first be spotted on schedule on Christmas night of 1758.
- Apr 26, 1803 - L'Aigle, France, in Lower Normandy,
experiences an historic meteorite fall, accompanied by "three
enormous detonations" and "a shower of fire". (Artist's
conception at right.) Three thousand stones were eventually
recovered in the area. The fall was notable because
Jean-Baptiste Biot was sent from Paris by the Académie
Française and the interior minister to investigate. His report
helped change the course of meteorite science: it established
the near-perfect elliptical shape of the strewn field (suggesting
the meteoroid came in at an angle), and his detailed chemical
analysis of the stones confirmed previous measurements of (other)
meteorites by Edward Howard showing their composition resembled
no known rocks on earth. Biot went on to make early discoveries
in both magnetism -- the Biot-Savart Law is still taught in
physics courses til this day -- and the polarization of light.
- Apr 26, 1920 - The famed Shapley-Curtis debate on the
scale of the universe and the nature and distance of "spiral
nebulae", aka galaxies, takes place before the Nat'l Academy of
Science in Washington, D.C.. Albert Einstein was one of the people
in attendance.
- Apr 27, 1961 - Explorer XI was launched, the first satellite
with a gamma ray detector. Only energies greater than 100MeV could
be detected, and in all less than 100 such photons were counted. The
result implied there was no prodigous matter-antimatter annihilation
going on in the universe (proton-antiproton in this case). The result
was mentioned by President Kennedy in his State of the Union speech
(1/31/1962). Paul Dirac had first raised the speculative possibility
of there being cosmic antimatter in his 1933 Nobel address.
- Apr 28, 2003 - NASA's Galaxy Evolution Explorer (GALEX)
satellite is launched, to study the history of star formation in
the universe through observations at ultraviolet wavelengths.
Featuring a 20" telescope and the first ever UV light dichroic
beam-splitter flown in space, the orbiting observatory primarily
made measurements in two bands: the near UV (1750–2800 Å)
and the far UV (1350–1740 Å). It did an all-sky imaging
survey, a deep imaging survey, and a survey of the nearest 200
galaxies. It also did three spectroscopic surveys. Though the
far UV detector failed after half a dozen years, the mission
duration was extended from an initial 2½ years to a total
of about a decade.
- Apr 30, 1006 - Visible in the night sky for three years,
the supernova of 1006 was seen around the world. It was likely the
brightest SN of historical times, being clearly visible during the
daytime, compared in brightness to a quarter moon, and said to be
so bright that "one could really see things clearly by its light"
(Chinese records). In 2003, astronomers with the National Optical
Astronomy Observatory estimated it might have had an apparent visual
magnitude of -7½.
The date comes from a description of the positions of the sun, moon,
and planets at the time by Ali ibn Ridwan (Egypt), who saw it as a
young boy. It was also recorded by monks at two monasteries in
Europe (Switzerland and Italy).
In 1965, Frank F. Gardner and Doug K. Milne at the Parkes radio
telescope associated the SN with the source PKS 1459−41, in the
constellation Lupus, in a paper in the Astronomical Journal.
The diameter is 20 parsecs, and no pulsar, neutron star, or black
hole has been found at its center, which is consistent with the
SN being of Type Ia, which in this case is thought to have involved
the merger of two white dwarf stars. Also known as G327.6+14.6, in
2010 the H.E.S.S. Gamma-Ray Observatory detected very-high-energy
gamma-ray emission from the remnant. A 2009 paper in New
Scientist detected the effect of the initial burst of gamma
rays in nitrate deposits in Antarctic ice.
©2002-2024, Chris Wetherill. All rights reserved. Display here does
NOT constitute or imply permission to copy, republish, or redistribute
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