Bone carvings keep track of phases of Moon. Early people engraved patterns
of lines on animal bones to keep track of the phases of the Moon. p.
17, F OV 1.6.
Mesopotamian ziggurats serve as observatories. Mesopotamian astronomers
made careful observations from the tops of pyramid-like towers called
Building of Stonehenge. The building of Stonehenge took place over many
centuries. Alignments of the stones at Stonehenge mark the rising and
setting points of the Sun at the solstices. p. 2.4, F 1.1, p. 32.
Temple of Amen-Ra at Karnak. The Temple of Amen-Ra at Karnak, Egypt was
built so that its main axis points to the sunset at the summer solstice.
Lunar eclipse observed at Ur in Mesopotamia. The oldest known recording
of a lunar eclipse took place at Ur more than 4000 years ago. p. 37, F
Chinese begin centuries long series of obs of eclipses. Chinese astronomers
recorded 900 solar and 600 lunar eclipses over a period of 2600 years.
Babylonians predict lunar eclipses. The Babylonians used their long record
of eclipses to see regular patterns of eclipses. They used these patterns
to predict lunar eclipses.
Hesiod describes practical uses for astronomy. Hesiod's poem The Works
and Days contains practical astronomical advice for navigation and for
Thales said to have predicted solar eclipse. The eclipse took place during
a battle between the Lydians and the Persians. They were so stunned by
the eclipse they ended the battle. p. 38, F 1.16.
Anaximander describes model of Earth, Sun, Moon, stars. Anaximander's
model was the forerunner of later Greek attempts to explain the heavens
in non-mythological terms.
Anaximenes proposes model of cosmos. In Anaximenes model the stars are
fixed to the inside of a solid vault surrounding the Earth. Later Greek
astronomers develop this idea into the concept of the celestial sphere.
Pythagoras and students develop model of solar system. The model of Pythagoras
used circular paths for the celestial bodies and assumed most celestial
bodies are spheres. p. 39.
Xenophanes concludes that the Earth is very old. Xenophanes reasoned
that stratified rocks were laid down as layers of sediments on the ocean
floor. Given the thickness of the rocks, he concluded that the Earth is
Herodotus concludes Earth is at least thousands of years old. Herodotus
reasoned that it would have taken millenia for the annual Nile flood to
have produced the Nile delta. p.160.
Lunar eclipse delays evacuation of Athenian army from Sicily. The Greeks
regarded eclipses as uncertain omens. The delay doomed the Athenian army.
Eudoxus explains retrograde motion. Eudoxus's explanation involved the
rotation of spheres in opposite directions. This geocentric model had
the Earth at its center. p. 36, F 1.14.
Aristotle argues celestial bodies are spheres. Aristotle used a number
of proofs that the Earth is a sphere, including the observation that its
shadow on the Moon during lunar eclipses is always a circle. p. 39-40,
Aristarchus finds relative dimensions of solar system. Aristarchus concluded
that the Earth was much smaller than the distances to the celestial bodies.
He also invented a heliocentric (Sun-centered) model for the solar system.
p. 41-44, F 1.20, F 1.21, F1.22
Eratosthenes finds circumference of Earth. Eratosthenes uses observations
of the altitude of the Sun to find the circumference of the Earth. His
estimate may have been accurate to within a few percent. p. 40-41, F 1.19
Hipparchus discovers precession, prepares stellar catalog. Hipparchus
compared his own observations with earlier ones to discover precession,
the slow change in the direction of the Earth's polar axis. He also made
what was probably the first catalog of the positions and brightnesses
of the stars.
c 0 AD
Building of Bighorn Medicine Wheel. Plains Indians of North America built
medicine wheels, monuments made of piles of stones. Alignments in the
medicine wheels often pointed toward the direction of sunrise at the winter
solstice. P. 28
Ptolemy "perfects" geocentric model of solar system. In Ptolemy's model
the planets moved on circles (epicycles) that moved on other circles (deferents).
The model could accurately predict the positions of the planets. Ptolemy
also compiled a catalog of stellar brightnesses based partly on the earlier
catalog of Hipparchus. p. 45-46, F 1.25 p. 365-366
Chinese record supernova that produces Crab Nebula. Chinese astronomers
observed a supernova that was visible in the daytime. The matter blasted
outward by the supernova later became observable as the Crab Nebula. p.
140-141, Box F 4.5
Comet Halley considered ill omen for King Harold. The appearance of Comet
Halley in 1066 was considered an ill omen for Harold, King of England.
Later that year Harold was killed in the Norman invasion of England. p.
309-310, F 10.8, F 10.9, F 10.10
Establishment of first universities in Europe. The development of astronomy
was aided by the birth of universities at Bologna, Oxford, Paris, and
a few other European cities.
Roger Bacon advocates experimentation. Bacon was among the first to recommend
experimentation as the best way to acquire scientific knowledge.
Dante describes medieval picture of universe in "Divine Comedy". Dante's
picture of the universe has the Earth at its center, surrounded by the
spheres of the Moon, Sun, planets, the fixed stars, a crystalline sphere
and, finally, paradise.
Jean Buridan develops impetus theory of motion. Buridan's theory of motion
was remarkable in that it contradicted the established ideas of Aristotle.
Oresme describes "Galilean" relativity. Oresme pointed out that we perceive
only relative motion and that the daily motion of the stars could be explained
either by the rotation of the Earth or the rotation of the celestial sphere.
Ulugh Beg builds observatory at Samarkand. Beg also compiled a star catalog
based on his own observations.
Regiomontanus uses printing to produce astronomy books and tables. Regimontanus
used the recently invented art of printing to produce books, almanacs,
and tables of predictions of the positions of the Sun, Moon, and planets.
Columbus uses lunar eclipse prediction to influence Arawaks. From his
almanac, Columbus knew that a lunar eclipse would occur on February 29.
He impressed the Arawaks with his accurate prediction that the Moon would
rise "inflamed with wrath".
Copernicus publishes "De Revolutionibus". De Revolutionibus, Copernicus's
description of his heliocentric model of the solar system, was published
two months before his death. p. 46-47, F 1.25, F 1.26, A1.26
Tycho observes supernova. Tycho's book about his observations of the
supernova established his reputation as an astronomer. p. 48-49
Tycho carries out best pre-telescopic observations ever. Tycho's observations,
made using specially built instruments, were the most accurate ever made
with the naked eye. Tycho also invented his own geocentric model of the
solar system. p. 48-49
Galileo begins experiments with falling and rolling bodies. Galileo's
experiments led him to conclude that once something is set in motion it
will remain in motion unless something stops it. This contradicted earlier
ideas that said only rest was a natural state. p. 53
William Gilbert proposes Earth has dipole magnetic field. Gilbert proposed
that the Earth acts like a big magnet whose field aligns the small magnet
used as a compass needle. p. 169
Giordano Bruno burned at stake. Bruno was tried before the Inquisition
and burned for heresy. Among his heresies was the idea that there were
Earth-like, inhabited planets orbiting the infinitely many stars. p. 47
Kepler observes supernova. The telescope was invented a few years after
Kepler carried out extensive naked-eye observations of the supernova of
1604. Since the invention of the telescope no supernovas have been observed
in the Milky Way.
Galileo uses telescope for astronomical observations. Galileo didn't
invent the telescope but he was among the first to use a telescope to
examine the heavens. He carried out important observations of the Sun,
Moon, Planets, and Stars. p. 51
Galileo observes Moon. Galileo found that the Moon had mountains, valleys,
and plains like the Earth. He called the dark regions of the Moon maria,
the Latin word for seas. p. 52
Kepler discovers laws of planetary motion. Working with Tycho's observations,
Kepler discovers the shapes of planetary orbits, how the speed of a planet
varies as it orbits the Sun, and the relationship between orbital distance
and orbital period. p. 49-50, F 1.28, F 1.29
Galileo observes phases of Venus. Galileo's found that Venus shows all
the phases from new to full. This observation was incompatible with the
Ptolemaic model of the solar system. p. 52, F 1.29
Galileo discovers four largest satellites of Jupiter. Galileo found that
Jupiter is orbited by four large satellites, now called, collectively,
the Galilean satellites. This proved that at least some celestial bodies
didn't orbit the Earth. p. 52
Francis Bacon suggests that Earth's continents move about. Bacon noticed
that the eastern and western shores of the Atlantic were parallel and
could be fitted together. p. 162-163, F 5.11, F 5.12, F 5.13, F 5.14.
Descartes develops concept of inertial motion. Descartes believed that
all motion resulted from collision with particles called "corpuscles".
In the absence of such collisions, a body remains at rest. An object in
motion continues to move in the same direction at the same speed. p. 80-81,
Galileo publishes "The Dialogue". The Dialogue, although superficially
a balanced debate about the merits of the geocentric and heliocentric
models of the solar system, was in fact a powerful argument for the ideas
of Copernicus. Galileo was brought before the Inquisition and spent the
last nine years of his life under house arrest. p. 53.
Maunder minimum. During the Maunder minimum almost no spots were seen
on the Sun. This was also a time of cold climate in Western Europe and
North America. p. 349, F 11.25
Bishop Ussher uses Bible to calculate age of Earth. From the chronology
of Biblical events, Ussher concluded that the Earth was created in 4004
BC. p. 160
Christiaan Huygens realizes that the "appendages" of Saturn are rings.
Huygens watched the appendages disappear in 1665 and reappear several
years later. He realized that the appendages were really flat rings that
disappeared when viewed edge on. p. 283, F 9.12
Giovanni Cassini discovers Great Red Spot of Jupiter. Although its size
and darkness have changed with time, the Great Red Spot has been continuously
present since the time of Cassini's discovery. p. 274-275, F 9.1
Robert Hooke shows that a central force leads to orbital motion. Hooke
used a pendulum to demonstrate to the members of the Royal Society that
in order to stay in orbit, the planets must be continually pulled toward
the Sun. p. 82.
Newton discovers law of universal gravitation. When Cambridge University
was closed by the plague, Newton spent most of the next two years at his
family farm. During this period he made fundamental discoveries in optics,
discovered the law of universal gravitation, and invented differential
and integral calculus. p. 85, F 2.7
G. Montanari notices brightness variations of Algol. Montanari saw that
Algol occasionally dropped to a third of its normal brightness. Later,
the drops in brightness were found to be caused by eclipses. p. 376
James Gregory makes the first realistic estimate of the distances of
the stars. Gregory assumed that the other stars were just as bright as
the Sun and then calculated how distant they had to be to match their
apparent brightnesses. p. 356-358, F 12.1, F 12.2
Christian Huygens proposes that light consists of waves. Huygens's ideas
were disputed by Newton, who proposed that light was mae up of a stream
of particles. p. 96-97. F. 3.1, A3.1
Edmund Halley predicts return of Comet Halley. Halley noted that comets
with similar orbits had appeared in 1456, 1531, 1607, and 1682. He proposed
that these were all the same comet and that it would return in 1758 or
1759 - which it did. p. 309-310, F 10.8, 10.9, 10.10
Newton publishes "Principia". Newton's monumental work described his
discoveries about gravity, motion and the orbits of the planets. p. 80-86,
F 2.2, F 2.3, F 2.4, F 2.5, F 2.6, F 2.7, F 2.8
Edmund Halley discovers stars move through space. Halley found that the
positions of stars change with time. He explained the changes in position
as due to the individual motions of stars through space. p. 463-466
James Bradley discovers the aberration of starlight. Bradley found that
the positions of all the stars shift back and forth as part of an annual
cycle caused by the motion of the Earth about the Sun.
William Herschel discovers Uranus. While measuring the directions and
brightnesses of stars, Herschel found a fuzzy spot that moved among the
stars. This was Uranus, the first planet that was not known to the ancients.
p. 54, p. 480
Charles Messier prepares list of nebulae. Like other comet hunters, Messier
often mistook nebulae for comets. He compiled a list of 103 nebulae as
an aid to other comet hunters. This was the first list of nebulae. p.
141, Box F 4.5, p. 480 (left out F 16.1)
John Goodricke discovers eclipses of Algol. Goodricke found that the
brightness declines of Algol occur at regular intervals. He proposed that
the brightness changes are due to eclipses of Algol by its binary companion.
William Herschel discovers speed and direction of Sun's motion. Herschel
analyzed the motions of seven bright stars and showed that part of their
motions was due to the motion of the Sun through space. p. 371-373, F
William Herschel uses star counts to map Milky Way. Herschel assumed
that the galaxy extended farther in directions in which he could see more
stars. He found the galaxy to be flattened with the Sun near the middle.
p. 447-448, F 15.4
Pierre Simon Laplace proposes stars can produce black holes. Laplace
proposed that if a star is so compact that its escape velocity exceeds
the speed of light, then not even light can escape from the star. p. 431
Giuseppe Piazzi discovers Ceres. Piazzi discovered Ceres, the first known
asteroid, on January 1, 1801, the first day of the 19th century. p. 304-307,
F 10.4, F 10.5, F 10.6, A 10.6
William Herschel shows many double stars are binaries. Herschel found
that for many pairs of stars, the orientation of the two stars changes
with time. The changes are a result of orbital motion. p. 374, F 12.13,
William Wolleston sees dark lines in solar spectrum. Wollaston passed
sunlight through a prism and noticed that there were numerous dark bands
and lines in the spectrum. p. 111-112, F 3.15
Meteorite shower at l'Aigle convinces scientists that meteorites have
an extraterrestrial origin. A careful investigation of the shower by Edouard
Biot convinced most skeptics that meteorites really do fall from the sky.
Denison Olmstead discovers shower meteors come from a common point in
the sky. Olmstead realized that the meteors seem to diverge from a point
in the sky because they originate in a swarm of meteoroids moving on parallel
paths through space. p. 315-316
Gaspar de Coriolis discovers Coriolis effect. The Coriolis effect, the
apparent deflection of moving bodies due to Earth's rotation, explained
many atmospheric circulation patterns. p. 172-173, F 5.21, F 5.22
h Carinae brightens to become second brightest star. h Carinae is normally
too faint to be seen, but between 1837 and 1860 it was the brightest star
in the sky.
Friedrich Bessel, Wilhelm Struve, Thomas Henderson measure the distances
of stars. Bessel, Struve, and Henderson, working independently, almost
simultaneously measured the parallaxes, and hence the distances, of nearby
stars. These were the first measurements, rather than estimates, of stellar
distances. p. 356-358
Christian Johann Doppler describes the Doppler effect. Doppler discovered
that the wavelength and frequency of a wave change if the source of the
wave moves toward or away from the observer. p. 114-115, F 3.18, A 3.18
Calculations of Adams and Leverrier lead to discovery of Neptune. Adams
and Leverrier independently calculated the location of the unknown planet,
Neptune, that was required to explain discrepancies in the orbit of Uranus.
p. 291-292, F 9.23
Jean Foucault uses pendulum to demonstrate Earth rotates. Foucault showed
that the pendulum swung in the same plane but the Earth rotated under
it, causing an apparent change in the direction of the pendulum's swing.
James Clerk Maxwell discovers velocity distribution function for a gas.
Maxwell showed that the distribution of velocities of the atoms or molecules
in a gas depends on temperature and the mass of the molecules.
William Huggins identifies chemical elements in stars. Huggins studied
the spectra of bright stars and found that the dark lines in their spectra
matched the wavelengths of atoms measured in terrestrial laboratories.
Asaph Hall discovers Phobos and Deimos. Remarkably, the prediction that
Mars had two small satellites was made by Jonathan Swift 151 years before
Hall's discovery. p. 264, F 8.24
Lord Kelvin and Hermann von Helmholtz estimate the age of the Sun. Kelvin
and Helmholtz independently calculated the length of time it would have
taken for the Sun to have shrunk to its present size. This time, called
the Kelvin-Helmholtz time, is about 20 million years. p. 336
Giovanni Schiaparelli discovers "canals" of Mars. Schiaparelli reported
thin, dark lines crisscrossing the surface of Mars. The discovery raised
the possibility of intelligent life on Mars. p. 264-265, F 8.25
Joseph Stefan finds the rate at which a blackbody emits energy. Stefan
found that the energy emitted by a blackbody increases as the fourth power
of temperature. p. 104-105.
Wilhelm Wien finds how temperature affects the color of a blackbody.
Wien found that a blackbody gets bluer as its temperature increases. p.
Max Planck presents formula of spectral distribution of a blackbody.
Planck found the way that the energy emitted by a blackbody depends on
its wavelength and the temperature of the blakbody. p. 104-105.
J. Hartmann finds interstellar absorption lines. Hartmann found a very
narrow line of calcium that didn't change in wavelength as the spectral
lines from the two stars in a binary star system shifted back and forth.
Albert Einstein explains the photoelectric efect. Einstein explained
that the emission of electrons only by light at short wavelengths occurs
because light consistes of bundles of energy called photons. p. 97, F
Einar Hertzsprung plots absolute magnitude versus spectral type. Hertzsprung
found that the stars are concentrated in a few regions of such a diagram,
which became known as an Hertzsprung-Russell (or H-R) diagram. p.
377-379, F 12.17, F 12-18.
Jacobus Kapteyn uses star counts to map Milky Way. Using star counts,
Kapteyn determined that the Sun lay 2000 pc from the center of a flattened
galaxy. p. 447-448
Henry Norris Russell independently invents H-R diagram. The H-R diagram
became an important tool for understanding the evolution of stars. p.
377-379, F 12.17, F 12-18
Alfred Wegener proposes continental drift. Wegener noted the similarity
of rocks on opposite sides of the Atlantic Ocean and proposed that the
present continents had been part of a supercontinent that broke apart
about 200 million years ago. p. 162-163, F 5.13
Albert Einstein's general theory of relativity. Einstein explained that
matter curves space, causing bodies to move in ways we attribute to gravity.
Karl Schwarzschild calculates geometry of black hole. Schwarzschild found
that if a massive body is compressed to a very small size it curves space
around it so severely that it forms a black hole. p. 431-432, F 14.12
100" Mt. Wilson telescope completed. The Mt. Wilson telescope was the
largest optical telescope in the world for 31 years until the Palomar
reflector was completed.
V. M. Slipher obtains radial velocities for 25 galaxies. Slipher found
that 21 of the 25 galaxies had red shifted spectral lines, indicating
that they are moving away from the us. p. 492-493, F 16.16
Harlow Shapley find the size and shape of the Milky Way. Shapley assumed
that globular clusters are distributed uniformly about the center of the
Milky Way. From this, he found that the Earth is located 15,000 pc from
the center of the Milky Way. p. 447-449, F 15.6
Annie J. Cannon and co-workers present thousands of stellar spectral
classifications in the Henry Draper Catalogue. Cannon and her co-workers
devised a classification system for stellar spectra and used it to produce
a catalog of spectra classifications for about 225,000 stars. p. 368-370,
M.N. Saha shows that the temperature of a star determines the appearance
of its spectrum. Saha showed that temperature differences rather are responsible
for the existence of different spectral classes of stars. p. 369
A. S. Eddington proposes that fusion powers the Sun. Eddington suggested
that the fusion of hydrogen, the most common element in the Sun, into
helium provides the enormous energy output of the Sun. p. 336.
Edwin Hubble shows spiral nebulae are galaxies. Hubble identified individual
Cepheid variable stars in spiral nebulae and used them to show that the
spiral nebulae are huge collections of stars far from the Milky Way. p.
481-485, F 16.1, F 16.3, F 16.4, F 16.5, F 16.6, F 16.7, F 16.8, F 16.9.
Cecilia Payne shows stars of different classes have essentially the same
chemical composition. Payne determined the chemical composition of a number
of stars of different spectral classes and found that they were nearly
the same. p. 369
Arthur Holmes proposes mantle convection drives continental drift. Holmes
proposed that convenction currents in the layer Beneath the Earth's crust
push the continents about. p. 161, F 5.10
Edwin Hubble discovers universe is expanding. Hubble found that the speed
of recession of galaxies increases with distance. He explained that this
is due to the expansion of the universe. p. 526-527, F 17.12
S. Chandrasekhar shows white dwarf stars are made of degenerate electrons.
Chandrasekhar also showed that the more massive a white dwarf, the smaller
it is and that there is a maximum mass, the Chandrasekhar limit, that
a white dwarf can have. p. 422
Clyde Tombaugh discovers Pluto. Tombaugh discovered Pluto by comparing
photographic plates taken of the same region of the sky about a week apart.
Pluto's image moved among the stars. p. 295, F 9.27, 9.28, 9.29
Robert Trumpler discovers diffuse interstellar dust. Trumpler found that
distant star clusters were bigger than nearby star clusters. He reasoned
that this was because interstellar dust made distant clusters look fainter
and, hence, more distant. p. 458-460, F 15.13, F 15.14, F 15.15, F 15.16.
Karl Jansky makes first radio astronomy observations. Jansky found that
the Milky Way galaxy is a source of radio emission. p. 469.
Grote Reber builds first radio telescope. Reber built the first antenna
specifically designed for radio astronomy. Using the radio telescope,
Reber made the first map of cosmic radio emission. p. 137-138, F
Robert Oppenheimer and George Volkoff calculate properties of neutron
stars. Oppenheimer and Volkoff calculated that a neutron star would be
only about 10 km in radius. p. 424-431, F 14.5, F 14.6, F 14.7, F 14.8,
F 14.9, F 14.10, F 14.11
H.C. van de Hulst predicts 21 cm line of interstellar hydrogen. van de
Hulst calculated that interstellar hydrogen atoms emit a spectral line
at a wavelength of 21 cm in the radio part of the spectrum. He suggested
that it would be possible to detect the 21 cm line using radio telescopes.
p. 462-463, Box F 15.1
200" Palomar telescope completed. The Palomar telescope was the world's
largest high quality optical telescope for over 40 years. p. 136
Jan Oort predicts existence of Oort Cloud of comets. Oort analyzed the
orbits of comets entering the inner solar system for the first time. He
proposed that these new comets originate in a cloud of comets tens of
thousands of astronomical units from the Sun. p. 307, F 10.11.
Harold Ewen and Edward Purcell detect 21 cm line. Ewen and Purcell used
a radio telescope to detect emission from interstellar hydrogen atoms. p.
462-463, Box F 15.1.
Gerard Kuiper proposes existence of Kuiper Belt of comets. Kuiper proposed
that the comets with periods of less than 200 years originate in a flatted
belt of comets whose inner edge lies just beyond the orbit of Neptune.
p. 311-312, F 10.11.
James Van Allen discovers Van Allen radiation belts. Explorer 1, the
first satellite launched by the United States, carried a Geiger counter
built by Van Allen. The Geiger counter showed that there are zones of
trapped energetic ions and electrons beyond Earth's atmosphere. p. 171-172,
Frank Drake uses radio telescope to search for interstellar signals.
Drake searched at a wavelength of 21 cm for artificial signals from creatures
on planets orbiting two nearby stars. No signals were detected. p. 462-463,
Box F 15.1.
Robert Leighton discovers solar oscillations. Leighton found that the
Sun vibrates at a variety of frequencies.
Harry Hess suggests mid-ocean ridges due to plate tectonics. Hess suggested
that the mid-ocean ridges occur where the ocean floor splits apart due
to plate tectonics and magma oozes out to form new ocean floor. p.
161-164, F 5.11
Horace Babcock proposes model for sunspot cycle. Babcock's model involved
the twisting of solar magnetic fields lines because the rate of solar
rotation varies with solar latitude. p. 346-347, F 11.23, 11.24, 11.25
Raymond Davis builds first solar neutrino telescope. Davis used a large
tank of cleaning fluid a mile deep in a gold mine to detect neutrinos
produced in nuclear reactions in the Sun's core. p. 339-340, F 11.12
Maarten Schmidt shows quasars have large redshifts. Schmidt found that
previously unidentified lines in the the spectrum of the quasar 3C 273
were actually redshifted lines of hydrogen. This showed that quasars are
moving rapidly away from us and are extremely distant. p. 500, Box
Arno Penzias and Robert Wilson discoverd cosmic background radiation.
Penzias and Wilson used a radio telescope to detect the highly redshifted
radiation from the early stages in the expansion of the universe. p. 521-522,
F 17.7, 17.8
C.-C. Lin and Frank Shu explain spiral arms of Milky Way. Lin and Shu
explained that the spiral arms are the crests of density waves that rotate
through the galaxy. p. 449-451, F 15.7, F 15.8.
Mariner 4 flies past Mars. Mariner 4 sent back pictures of Mars that
showed a deal planet whose surface resembled that of the Moon. p. 257-258,
Jocelyn Bell and Antony Hewish discover pulsar. Bell and Hewish discovered
regular pulses of radio radiation from a point in the sky. The pulses
were later attributed to beams of radiation emitted by a rotating neutron
star. p. 425, F 14.6
Astronauts Edwin Aldrin and Neil Armstrong land on Moon. On July 20,
1969 Aldrin and Armstrong became the first people to land on the Moon.
Last Apollo mission to Moon. Apollo 17 concluded the series of lunar
landings in which a dozen astronauts explored the Moon.
Voyagers 1 and 2 reach Jupiter. The Voyagers used gravitational boosts
from their encounters with Jupiter to speed outward to encounters with
other planets in the outer solar system. p. 278, F 9.5
Mariner 10 encounters Mercury. After passing Venus, Mariner 10 encountered
Mercury four times, sending back pictures of Mercury's surface. Mariner
10 is the only spacecraft that has flows past Mercury.
Vikings land on Mars. The two Viking landers safely touched down on Mars's
surface and, for several years, returned images of the surface, as well
as meteorological and seismic data. The Vikings also carried life-detection
experiments. p. 264-265.
International Ultraviolet Explorer (IUE) launched. IUE has been in operation
for over 20 years, sending back ultraviolet spectra of celestial objects. p.
142-143, F 4.15
James Christy discovers Pluto's moon, Charon. Chrisy noticed that Pluto's
image had a bump on it. The bump proved to be a satellite, Charon. p.
295-296, F 9.27
Very Large Array begins operations. The Very Large Array (VLA) is an
array of 27 radio telescopes that work together to produce radio images
that are comparable to those of traditional optical telescopes.
Alan Guth proposes early period of inflation of universe. Guth proposed
that the a number of difficulties with the standard model of the expanding
universe could be explained by an enormous expansion very early in the
history of the universe. p. 532-533.
Fleet of space probes encounters Comet Halley. A fleet of five space
probes flew past Comet Halley at distances as small as 600 km. Images
sent back by the spacecraft showed that the nucleus of Halley is very
dark and larger than anticipated. p. 310, F 10.10.
Kamiokande neutrino telescope begins operating. Shortly after it was
completed, the Kamiokande telescope was one of two neutrino telescopes
to detect neutrinos from a supernova in the Large Magellanic Cloud.
Supernova detected in Large Magellanic Cloud. The supernova, which occurred
in one of the nearest galaxies, was the first supernova in almost 400
years that could be seen without the aid of a telescope. p. 409.
Hipparcos satellite begins making observations. Hipparcos made highly
accurate measurements of the positions and parallaxes of stars. p. 517.
Magellan begins radar mapping of Venus Magellan produced an almost complete
radar map of the surface of Venus. p. 254-255, F 8.12, F 8.13
CCDs become the detector of choice in astronomy. CCDs are much more sensitive
than photographic plates and allow astronomers to detect very faint objects.
Hubble Space Telescope launched. The HST has produced images of breathtaking
clarity and has allowed astronomers to see light from more distant objects
than ever before. p. 142-143, F 4.15, F 4.16
ROSAT launched. ROSAT produced X-ray images of hot, X ray emitting objects.
p. 142, F 4.15
First Keck 10-m telescope completed. The Keck telescope, unlike most
earlier large optical telescopes, has a mirror made of many hexagonal
segments. There are now twin Keck telescopes on Mauna Kea. p. 125-126,
p. 133, F 4.8
Hubble Space telescope launched.
Galileo obtains first up-close images of asteroid (Gaspra). The Galileo
spacecraft passed Gaspra at a distance of only 1,600 km. Images from Galileo
showed craters and groovelike cracks. p. 305, F 10.5
Very Long Baseline Array completed. The Very Long Baseline Array (VLBA)
is an array of ten radio telescopes that work together to yield radio
images with even better resolution than optical telescopes can achieve.
Fragments of Comet Shoemaker-Levy 9 strike Jupiter. Tides due to Jupiter
broke Comet Shoemaker-Levy 9 into at least 18 fragments that later struck
Jupiter, producing bright fireballs and new cloud features. p. 286
Galileo probe enters Jupiter's atmosphere. An entry probe detached from
the Galileo spacecraft and parachuted into Jupiter's atmosphere. The probe
sent back data for about an hour before it was destroyed by high pressure
and temperature. p. 274, p. 281
Infrared Space Observatory (ISO) launched. ISO obtained high resolution
infrared spectra and images of cool bodies and clouds of dust in the solar
system, galaxy, and beyond. p. 142-143, F 4.15
Planets found orbiting stars like the Sun. Astronomers in the United
States and Switzerland reported the first detections of Jupiter-like planets
orbiting nearby Sun-like stars.
Claim of evidence for fossil life in Martian meteoroid. A meteorite blasted
from Mars by an asteroidal impact was found to contain possible fossil
traces of ancient biological activity and life-like structures. p. 265
Pathfinder lands on Mars, Mars Global Surveyor begins mapping of Mars.
The Pathfinder lander and the Sojourner rover it carried landed in an
ancient Martian riverbed. The Mars Global Surveyor is sending back pictures
of Mars that have unprecedented clarity and detail. p. 257-264
Lunar Prospector obtains evidence of possible water on the Moon. p. 196
Japanese researchers find evidence that neutrinos (possible candidate
as "dark matter") may have mass. p.495
Gamma ray bursts proven to originate in distant galaxies, not our own,
thus deepening the mystery of their origin and power. p. 140.
Astronaut John Glenn returns to space aboard the Shuttle Discovery in
NASA received a double set-back when first the Mars Climate Orbiter and
then the Mars Polar Lander space craft fail. P. 257 (Mars)
Lunar Prospector intentionally crashed into Moon in attempt to identify
water. None is found. p. 188.
NEAR spacecraft orbits an asteroid (Eros) for the first time. p. 304.
Spacecraft NEAR-Shoemaker makes historic first landing on the asteroid
(Eros). p. 304.
Leonid meteor storm on November 18. At times near the peak of shower, up to 5 or 6 meteors could be seen per second.
Sudbury neutrino detector in Canada demonstrates that neutrinos emitted from the Sun's
core change their type as they travel to Earth. This resolves the many decade long mystery
of the "missing solar neutrinos" and proves these tiny particles have mass.
Observations from a spacecraft orbiting Mars suggest large deposits of ice may lie below
the Martian surface.