An Astronomical Timeline

Compiled by Brian Timmins

Page Two of Five

Page 1	Pre-Recorded History to 1682
Page 2	1683 - Newton's "Principia" to 16thJuly, 1968
Page 3	20th July, 1969 - Armstrong & Aldrin on the Moon to the end of the 20th century
Page 4	1st January 2001 to the 31st December 2007
Page 5	1st January 2008... Onwards and Upwards...

Goto The Eighteenth Century Goto The Nineteenth Century Goto The Twentieth Century (up to 16 July 1968)

Modern Astronomy - The Last Years Of The Seventeenth Century

1687

Isaac Newton publishes his theories on gravity. The era of modern physics and astronomy is inaugurated by the publication of his "Mathematical Principles of Natural Philosophy", commonly called The Principia. It was published in Latin and did not actually appear in English until 1729. It discusses the laws of mechanics and the law of gravity and also describes discoveries about the motion and the orbits of the planets.

1688

Newton constructs the first reflecting telescope.

1690

End of the Copernical Revolution.

Modern Astronomy - The Eighteenth Century

1704

First observatory at Cambridge University (based at Trinity College).

Isaac Newton publishes his "Opticks" describing (among other things) his work with prisms.

1705

Daniel Defoe publishes "Journey to the World in the Moon".

1718

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.

1724

Scottish astronomer-mathematician James Gregory (1638-1675), Professor of Mathematics in the University of St Andrews. Gregory described his design for a telescope in his 1663 publication Optica Promota (The Advance of Optics).

John Hadley constructs the first working telescope to the Gregorian design.

George Berkeley suggests that space exists because of the matter in it.

1724-1743

Sawai Jai Singh II, the remarkable Monarch of Jaipur, who was a mathematician, an astronomer, and a town planner par excellence, plans the famous Indian observatories at Jaipur, Delhi, Mathura, Ujjain and Varanasi and were completed between 1724 and 1743. The one at Jaipur was the largest with the maximum number of instruments. They were collectively known as Jantar Mantar (Magical Device). .

1725

Joseph-Nicolas Delisle under instruction from the Empress Caherine, founded the St. Petersburg observatory.

The most accurate star catalogue compiled to date is published by John Flamsteed.

1728

Halley discovers that some stars have moved since antiquity. This is the proper motion of the stars.

1729

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.

1730s

James Short succeeds in producing high-quality telescopes to the Gregorian design.

1733

Chester Moor Hall invents the achromatic lens refracting telescope.

1740

Dr. W. Stukely notices that the design of Stonehenge is oriented around a solstice alignment. Originally thought to be based on the Summer Solstice, in the late 20th century and early 21st, a more satisfying theory that it was based on the winter solstice was propounded.

1745

Georges Buffon proposes the first of the catastrophic theories of the formation of the solar system.

1750

Discussion of the shape of the Milky Way and other galaxies promoted by Thomas Wright.

1753

Thomas Zebrowski (1714-1758) returned to Vilnius from advanced studies in Vienna and Prague. He designed a plan of an astronomical observatory and received means from a noblewoman and benefactress Elzbieta Oginska-Puzynina for its construction.

1754

Nicolas Louis de Lacaille made nearly two thousand additions to his star catalogue

The heliometer, a device designed to measure the diameter of the sun, is invented by John Dollond. It is also used to measure distances between stars.

1758

John Campbell invents the sextant.

1757

Dolland re-invents the chromatic lens. As predicted by Edmund Halley, the 1682 comet returns, is observed by the astronomer Johann Palitzsch on the night of December 26-27, and is thereafter named Halley's Comet.

1761

Joseph-Nicolas Delisle built 63 observing station network for observing the transit of Venus.

Mikhailo Vasilevich Lomonosov discovered the atmosphere of Venus.

1762

James Bradley publishes a star catalogue, containing the measured positions of 60,000 stars.

1767

John Michell postulated the existence of physical binary stars.

1771

Charles Messier publishes a list of nebulae.

1772

Johann Bode published his popular book, "Anleitung zur Kenntnis des gestirnten Himmels" [Instruction for the Knowledge of the Starry Heavens]. In this book, he stressed an empirical law on planetary distances, originally found by J.D. Titius (1729-96), now called "Bode's Law" or "Titius-Bode Law". This law concerns the empirical relationship between the mean distances of the planets from the sun.

1775

Sir William Herschel constructs the largest reflecting telescope at that time - 40 foot, and discovers star clusters and nebulae.

1780

Florence Specola observatory built.

1781

Charles Messier catalogs galaxies, nebulae and star clusters, starting the Messier numbering, or M numbering, system; then publishes his catalogue. 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.

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.

1783

Jesse Ramsden invents his eponymous eyepiece.

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, presents at the Royal Society and publishes "On the Proper Motion of the Sun and Solar System; With an Account of Several Changes That Have Happened among the Fixed Stars since the Time of Mr. Flamstead". He analyzed the motions of seven bright stars and showed that part of their motions was due to the motion of the Sun through space.

1784

John Mitchell postulated the existence of black holes.

1785

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 and discovered the direction of our Sun toward the solar apex.

1787

Caroline Lucretia Herschel (sister of William Herschel) became the first woman officially recognized for a scientific position when she was given a £50 per year salary by King George III. In 1783 she discovered three new nebulae. Today, these objects are know as NGC 2360, NGC 205, and NGC 253. On August 1, 1786, Caroline discovered her first comet

1789

William Herschel finishes a 49-inch (1.2-meter) optical reflecting telescope, located in Slough, England.

1790

Pierre Simon Laplace proposes stars can produce black holes. Laplace proposed that if a star is so dense that its escape velocity exceeds the speed of light, then not even light can escape from the star.

1794

Ernst Florens Friedrich Chladni, the founder of meteoritics, published a small book asserting that masses of iron and of rock actually do fall from the sky, producing fireballs when heated by friction with the air. He concluded that they must be cosmic objects, thus postulating for the first time - meteorites.

1796

Laplace publishes his theory of the origin of the solar system and develops the theory of the origin of the universe.

1798

Henry Cavendish (1731 1810) first measures the force of gravity between two objects in his laboratory.

1799

Laplace publishes "Treatise on Celestial Mechanics".

Modern Astronomy - The Nineteenth Century

1801

Thomas Young publishes proof of the principle of interference of light, supporting the wave theory of light. The first asteroid is discovered when Giuseppe Piazzi identifies Ceres. He discovered Ceres, the first known asteroid, on January 1, 1801, the first day of the 19th century.

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.

1802

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.

1803

John Dalton, a chemist, argues that observations in chemistry require matter to be composed of atoms.

A 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.

1804

William Herschel proved the existence of physical binary stars with the discovery of a second star orbiting Castor.

1817

Joseph Fraunhofer discovers absorption lines in the Sun's spectrum.

1820

The Royal Astronomical Society is founded.

1833

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.

1835

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.

As a result of his measurements of stellar parallax and his accurate observations of double stars, Friedrich Georg Wilhelm Struve resolved some stellar paradoxes.

1837

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.

1838

Friedrich Bessel, Wilhelm Struve, Thomas Henderson, working independently and almost simultaneously, calculate the distance of 61 Cygni from the Earth at approximately 6 light years away (the real value is nearer 12 light years). They also measure the distances of other stars using the parallax method. These were actual measurements using the baseline of the earth's orbit. As`a result, Stellar parallaxes arediscovered.

1840

J.W. Draper "invents" astronomical photography and makes the first daguerreotype image of the Moon.

1842

Christian Johann Doppler describes the Doppler effect. He discovered that the observed wavelength and frequency of a wave change if the source of the wave moves toward or away from the observer.

1843

Samuel Heinrich Schwabe recognises sunspot cycles.

1844

Freidrich Bessel discovers a white dwarf star orbiting Sirius.

1845

Lord Rosse finishes the Birr Castle 72-inch optical reflecting telescope, located in Parsonstown, Ireland and discovers a spiral shaped nebula.

1846

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.

Neptune is discovered by Johann Gottfried Galle.

1847

A 15-inch refracting telescope is built in Cambridge, Massachusetts .

1849

Carl Kellner designs and manufactures the first achromatic eyepiece, announced in his paper "Das orthoskopische Ocular".

Santiago observatory set up by USA, later becomes the Chilean National observatory.

1850

Edward Roche calculates Roche's limit. William Bond takes the first photographic image of a star (Vega).

1851

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.

The 11 year sunspot cycle (observed in 1843 by Heinrich Schwabe) is generally recognized.

1854

Hermann von Helmholtz proposes that the Sun derives its energy from gravitational shrinkage.

1859

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. He also discovered that Saturn's rings are not solid.

R. Bunsen and S. Kirchoff discover spectral analysis which explains the dark lines in the Sun's spectrum.

1860-1863

Sir William Huggins studies the chemical composition of stars using spectral analysis.

D. Donati maps spectra of stars.

Georg Simon Plössl produces his eponymous eyepiece.

1862

Alvan Clark is the first astronomer to identify a white dwarf star.

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.

1863

Huggins uses stellar spectra to suggest that the same elements are found in the stars and Earth.

1864

Herschel's so-called GC (General Catalogue) of nebulae and star clusters published.

William Hugens discovered emission lines in the spectra of some nebulae that matched no known elements.

1865

Jules Verne publishes "De la Terre à la Lune" - From Earth to Moon, mentioning the exact velocity that the cannon that shot the three travelers to the moon must be seven miles a second to escape the Earth's gravity.

1866

Giovanni Schiaparelli discovered that the comet 1862 III was causing the Perseid meteor showers.

1868-9

Pierre Janssen and Norman Lockyer used the spectroscope to study solar prominences and independently discover the Helium line in the Sun's spectrum.

W. Huygens discovers the radial velocity of stars.

Norman Lockyer also finds that the yellow spectral line observed in the Sun's spectrum during the 1868 eclipse must belong to a new element, later named helium.

Father Angelo Secchi produces the first maps of Mars showing the markings later called "canali" by Schiaparelli.

1871

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.

German Astronomical Association organized network of 13 (later 16) observatories for stellar proper motion studies.

1872

Henry Draper invents astronomical spectral photography and photographs the spectrum of Vega.

1875

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.

1877

Giovanni Schiaparelli observed lines on the surface of Mars which he called "canali". These were later called "Canals" because of a misunderstanding by English speaking people. The Italian word "canali" means channels or grooves, something completely natural.

1878

Dreyer published a supplement to the GC of about 1000 new objects.

The Great Red Spot on Jupiter is named. During this year it increases in size.

1879-80

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 - E=σT⁴.

1880

Ernst Abbe designs the first orthoscopic eyepiece (Kellner's was solely achromatic rather than orthoscopic, despite his description).

1885

Supernova SN1885A (S Andromeda) is first such phenomenon studied in several centuries.

1887

First photographic star charts produced.

Paris conference institutes Carte du Ciel project to map entire sky to 14th magnitude photographically.

AA Michelson and EW Morley experimentally demonstrate the constancy of the speed of light.

Norman Lockyer classifies stars by age.

1888

First usage of 91cm refracting telescope at Lick Observatory, on Mount Hamilton near San Jose, California.

Johann L.E. Dreyer publishes "A New General Catalogue of Nebulas".

1889

Astronomical Society of the Pacific founded Mizar A is discovered to be a spectroscopic binary star.

1890

Williamina Paton Stevens Fleming, using a technique that came to be known as the Pickering-Fleming system, compiles and publishes the first volume of "The Draper Catalogue of Stellar Spectra". The second volume came in 1897.

Albert Michelson proposes the stellar interferometer

1892

George Ellery Hale devises the "spectroheliograph" taking pictures of the Sun in the light of a single spectral color.

1894

Wilhelm Wien finds how temperature affects the color of a blackbody. Wien found that a blackbody gets bluer as its temperature increases.

1895

James Keeler discovered that Saturn's rings rotate at different speeds.

Percival Lowell describes the canals of Mars in his book "Mars".

Konstantin Tsiolkovsky publishes a series of papers describing space flight.

1896

Antoine Becquerel discovers radioactivity.

1897

The Yerkes 1 metre refractor opens at Williams Bay, Wisconsin, under the auspices of the University of Chicago. It is still the largest refracting telescope in the world, and likely to remain so as its size is near to the limit of non-deformation for glass.

1898

H. G. Wells publishes "War of the Worlds".

Wilhelm Wien postulates "Wien's Approximation", also sometimes called Wien's law or the Wien distribution law, which is a law of physics used to describe the spectrum of thermal radiation - frequently called the blackbody function.

1900

Max Planck in Berlin is studying something called the "ultraviolet catastrophe", and, to use his own words "as an act of desperation" proposed that light did not really come in waves but existed as specific amounts, or "quanta", of energy. Then, in a lecture to the German Physical Society, announces that matter absorbs heat energy and emits light energy discontinuously and depends on its wavelength and the temperature of the blackbody; thus giving birth to quantum mechanics.

Modern Astronomy - The Twentieth Century up to 1968

1901

Kapteyn calculates the size of the stellar system.

1902

James Jeans calculated the point at which gravitational collapse would begin based on cloud temperature and mass.

First publication of Draper star catalogue

1903

Orville Wright launches first powered flight in history, flying at Kitty Hawk for 12 seconds - 4 flights were made on 17 December. The length of his first flight is less than the wingspan of a jumbo jet.

Earlier that year, Russian physicist Konstantin Eduardovich Tsiolkovsky claimed, with complex mathematical theories that man will one day travel in space and occupy planets. He publishes "The Investigation of Outer Space by Means of Reaction Apparatus".

1904

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.

Mount Wilson Observatory is founded. Its prime objective is to study the sun.

Kapteyn discovers star-streams.

Observatories of the Carnegie Institution of Washington founded

1905

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. He publishes his "Special Theory of Relativity".
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.

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.

1906

William Morgan suggests that the Milky Way has a spiral structure.

Hertzsprung plots the color and luminosity of the Pleiades.

1907

The 60-inch reflector opens on Mt. Wilson, California.

1908

Cosmic distance scale formulated by Henrietta Leavitt.

Danish astronomer Hertzsprung details dwarf and giant stars.

George Ellery Hale finds that sunspots must be intensely magnetic.

Henrietta Swan Leavitt discovers stars that go through cycles of brightness and darkness, the cepheid variables.

Meteorite impact in Siberia, June 30.

Mizar B is discovered to be a spectroscopic binary star

1910

George Willis Ritchey and Henri Chrétien co-invent the Ritchey-Chrétien telescope used in many, if not most of the largest astronomical telescopes.

1911-1914

Ejnar Hertzsprung and Henry Norris Russell publish their diagram that plots the stars brightness against their temperature. This is called the HR diagram.

1912-1922

V.M. Slipher measures the red shift of spiral nebulae.

1912

Leavitt discovers the periods of Cepheid variables.Henrietta S. Leavitt discovered the relationship between the period of variation and the average luminosity of Cepheid variable stars.

1913

Hertzsprung is the first person to measure the distance to an object outside the Milky Way (The Small Magellanic Cloud) using the variable delta-Cepheid stars.

Henry Norris Russell independently invents H-R diagram. The H-R diagram became an important tool for understanding the evolution of stars.

1914

Robert Goddard launches a ten foot rocket that begins the rocket era. Arthur Eddington suggests that the spiral nebulae are galaxies.

1915

Adams describes the attributes of a white dwarf star 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.

Discovery of Proxima Centauri, the nearest non-Solar star to the Earth

1916

Albert Einstein's general theory of relativity, first static cosmological model, cosmological constant. (Note: Galaxies not yet discovered by astronomers) Einstein explained that matter curves space, causing bodies to move in ways we attribute to gravity.

van Maanen measures the roatation of spiral nebulae.

Edward Barnard discovered a star with the fastest known proper motion; this was later named Barnard's Star.

Karl Schwarzschild solves Einstein's theory of general relativity and determines what is now called the Schwarzschild radius. He calculates the geometry of a black hole and finds 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. The distance from the black hole from which there is no escape, not even for light, is the Schwarzschild radius.

1917

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.

Einstein and de Sitter formulate their cosmological theories.

Shapley uses globular clusters to calculate the size of the Milky Way.

1918

American astronomer Harlow Shapley discovers the shape and size of the Milky Way.

Annie Cannon begins publication of the Henry Draper Catalog.

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 spectral classifications for about 225,000 stars.

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.

1919

Edward Barnard publishes a catalogue of dark nebulae.

International Astronomical Union (IAU) founded.

The bending of starlight, caused by the gravity of the Sun, is measured during a Solar eclipse. Eddington "proves" that the Theory of Relativity is correct by measuring this small deflection caused by the Sun's gravitational field.

1920

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. He begins his study of the matter between the stars.

The first measurement of the diameter of stars using interferrometry.

The Shapley & Curtis debate on the size of the universe .

M.N. Saha shows that the temperature of a star determines the appearance of its spectrum. i.e. These temperature differences are responsible for the existence of different spectral classes of stars.

1922

Russian physicist/mathematician Alexander Freedmann predicts on the basis of the Theory of Relativity, that the universe is expanding.

1923

Edwin Hubble identified and measured the periods of the Cepheid variables. He also shows spiral nebulae are galaxies. He 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.

1924

Andromeda galaxy discovered where astronomers previously believed a nebula existed. Edwin Hubble determines that spiral nebulae are distant galaxies outside the Milky Way and calculates the distance to the Andromeda nebula. He categorizes the galaxies by type. He proves that galaxies are systems independent of the Milky Way.

Arthur Eddington suggests that white dwarf stars are made of degenerate matter

1925

Eddington publishes his explanation of the inner structure of the stars and derives the mass-luminosity law.

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.

Walter Adams identified Sirius B as a white dwarf star

1926

Henry Norris Russell and H. Vogt independently postulate the Russell-Vogt theorem.

Robert Goddard uses liquid rocket fuel to power a test rocket.

Bertil Lindblad, a Swedish astronomer, suggests that our galaxy rotates

1927

Jan Oort showed that the Milky Way galaxy rotates.

Lemaitre proposes his quantum theory of the origin of the universe. Big Bang theory begins, as he proposes that the Universe must have begun to expand from what he describes as a small cosmic egg.

S. Bowen discovered the forbidden spectral emission lines.

1928

Dirac solved the equations that describe the quantum behavior of electrons leading to a theory of the existence of antimatter.

Arthur Holmes proposes mantle convection drives continental drift. He proposed that convection currents in the layer beneath the Earth's crust push the continents about.

1929

Georges Lemaitre theorizes that the universe was once the size of an atomic nucleus and suddenly expanded ("big bang" theory). Hubble discovers the ratio between the galaxies' distance and radial speed and observes that all galaxies are receding from each other at speeds proportional to their distances and concludes that the universe is expanding, thus giving rise to what becomes known as "Hubble's constant".

Robert Goddard launches an atmospheric research rocket.

Edwin Hubble concludes from astronomical observations that distant galaxies recede from us in all directions, and that therefore the universe is expanding. He found that the speed of recession of galaxies increases with distance, and that this is the result of the expansion of the universe.

1930

Bernard-Ferdinand Lyot invents the coronagraph

Bernhard Schmidt invents the Schmidt Camera.

Karl Jansky builds a 30-meter long rotating aerial radio telescope

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.

Robert Trumpler discovers diffuse interstellar dust. He 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.

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.

1931

J. Trumpler proved that interstellar dust was preventing observation of distant stars. Karl Jansky invents radio astronomy and discovers radio waves that are extra-terrestrial in origin.

1932

Astronomers at the Mt. Wilson observatory discovered that Venus' atmosphere was largely carbon dioxide.

Jansky built the first radio telescope.

Chandrasekhar describes a possible mechanism for the collapse of stars and the formation of white dwarfs, neutron stars and black holes

1933

Arthur Eddington published "Expanding Universe".

Bernard-Ferdinand Lyot invents the Lyot filter

1934

Baade and F. Zwicky postulated that supernovae precede neutron stars.

Bernhard Schmidt finishes the first 14-inch Schmidt optical reflecting telescope

1936

Grote Reber began mapping the Milky Way galaxy with a radio telescope.

Hubble publshes "The Realm of the Nebula".

Palomar 18-inch Schmidt optical reflecting telescope begins operation, located on mount Palomar, California

1937

Grote Reber builds a 31-foot radio telescope - the first antenna specifically designed for radio astronomy. Using the radio telescope, Reber made the first map of cosmic radio emission.

1938

Orson Wells broadcasts "War of the Worlds" October 30.

Bethe and von Weizsacker identify the carbon-nitrogen cycle of nuclear fusion and describe the production of energy in stars.

Robert Oppenheimer and R. Serber demonstrate that collapsed stars could form stars denser than white dwarfs.

1939

Bengt Stromgren discovered a method of calculating the radius of ionized regions surrounding stars.

Frank J Whittle invents the jet engine.

Robert Watson-Watt invents radar.

Oppenheimer and Snyder publish a detailed paper suggesting that black holes result from the collapse of massive stars.

Robert Oppenheimer and George Volkoff calculate properties of neutron stars. They calculate that a neutron star would be only about 10 km in radius.

1941

Dmitri Maksutov invents the Maksutov telescope which is adopted by major observatories in the Soviet Union and internationally. It also became a popular design with amateur astronomers

1944

Dmitri Dmitrievich Maksutov invents the Maksutov telescope.

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.

Himple discovers T Tauri stars.

1945

Radar contact is established with the Moon. Arthur C Clarke proposes communications satellites in geosynchronous orbit above the Earth (and wishes he had patented it) - by 1965 his visionary ideas become reality.

1946

Martin Ryle and his group perform the first astronomical observations with a radio interferometer.

1947

Bernard Lovell and his group complete the Jodrell Bank 218-foot non-steerable radio telescope.

Chuck Yeager breaks the sound barrier in the Bell X-1 rocket plane.

1948

The 200 inch Hale telescope completed and installed at Mount Palomar.

It was the world's largest high quality optical telescope for over 40 years.

Gold and Hoyle propose the "steady-state theory".

Gamow proposes the "Hot Big Bang" theory.

1949

Palomar 200-inch optical reflecting telescope (Hale telescope) begins regular operation, located in Palomar, California.

Palomar 48-inch Schmidt optical reflecting telescope begins operation.

Term Big Bang is first used by Fred Hoyle.

Rocket testing ground is established at Cape Canaveral.

1950

Jan Oort predicts existence of Oort Cloud of comets. Oort analyzed the orbits of comets and maps those 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.

Whipple postulates the dirty iceberg model of comet nuclei.

1951

First space flight by living creatures when US sends 4 monkeys into the stratosphere.

Walter Baade and Rudolf Minkowski discover the first known radio galaxy - Cygnus A.

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.

Harold Ewen and Edward Purcell detect 21 cm line. Ewen and Purcell used a radio telescope to detect emission from interstellar hydrogen atoms.

1952

Allan Sandage at Hale Observatories estimates the age of the universe at 20 billion years.

1954

Earth rotation aperture synthesis suggested (see e.g. Christiansen and Warburton (1955))

1955

Radio emissions from Jupiter are detected, mystify observers. They later turn out to come from the planet's radiation belt.

1956

Palomar sky survey completed

1957

• 24 April: Patrick Moore's Sky at Night was first televised. He has introduced, ever since, every single program except one when he was ill. Thus he is the longest running presenter, and the program is the longest running program, in the world
• 4 October: Sergei Korolyov of the Soviet Union launches Sputnik I, the first satellite to orbit the Earth
• 3 November: Launch of Sputnik 2, carrying a dog named Laika

Bernard Lovell and his group complete the Jodrell Bank 250-foot (75-meter) steerable radio telescope.

Peter Scheuer publishes his P(D) method for obtaining source counts of spatially unresolved sources.

Publication of 'Synthesis of the Elements in Stars' by Margaret Burbidge, Geoffrey Burbidge, William Fowler, and Fred Hoyle (B2FH); this landmark paper suggested that stellar elements are formed by nuclear reactions.

1958

• 31 January: Launch of Explorer 1
• 26 March: Launch of Explorer 3
• 1 May: US National Academy receives from James Van Allen a report on the discovery of the radiation belt

Eugene Parker proposes the existence of a "solar wind."

NASA established by US President Eisenhower.

"Project Orion" to design nuclear powered spaceships.

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.

1959

• 2 January: Luna 1 launched by Soviet Union, comes within 6000 km of Moon

First pictures of far side of the moon by Luna III.

Lick Observatory completed.

Soviet Union lands the first probe on the Moon.

Radio Observatory of the University of Chile, located at Maipú founded

The 3C catalogue of radio sources is published (revised in 1962)

The Shane 120-Inch Telescope Opened at Lick Observatory

1960

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.

Owens Valley 27-meter radio telescopes begin operation, located in Big Pine, California.

Robert Leighton discovers solar oscillations. Leighton found that the Sun vibrates at a variety of frequencies.

Archaeoastronomy, the study of the history of astronomy, is introduced at universities.

1961

• 12 April: Yuri Gagarin becomes first human to orbit Earth on the spaceship Vostock I
• 5 May: Allan Shepard becomes first American in space, completes 15 minute suborbital hop
• 25 May: US president J.F. Kennedy announces project to land human on Moon within decade

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.

Parkes 64-metre radio telescope begins operation, located near Parkes, Australia

1962

• 20 February: John Glenn becomes pilots the Mercury-Atlas 6 spacecraft into a three-orbit flight around the Earth
• 26 April: Ariel 1. The honor of the first astronomical satellite project goes to Great Britain. Investigated Solar UV and X-radiation, and obtained an energy spectrum of primary cosmic rays.
• 14 December: Mariner 2 passes by planet Venus

European Southern Observatory (ESO) founded.

Green Bank 90m radio telescope goes into operation.

Kitt Peak solar observatory founded.

The first X-ray source is discovered in Scorpius and Venus' retrograde rotation discovered.

1963

Arecibo 300-meter radio telescope begins operation, located in Arecibo, Puerto Rico.

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.

Maarten Schmidt discovers the first quasar and 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.

The first planet orbiting another star (Bernard's star) is discovered.

The quark theory of the structure of matter is published.

Valentina Tereshkova, the first woman in space, made 48 orbits of the Earth in the Vostok 6 spaceship.

1964

• 27 March: Ariel 2. Investigated astronomical objects in the radio range.

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.

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.

Martin Ryle's 1-mile radio interferometer begins operation, located in Cambridge, England

1965

• 23 March: first Gemini flight, carrying 2 US astronauts together
• 14 July: Mariner 4 flies above Mars. It sent back pictures of Mars that showed a deal planet whose surface resembled that of the Moon

Cosmic background radiation discovered by Wilson and Penzias.

HARP cannon operated on Barbados. The High Altitude Research Program (HARP) was unique in the history of the space age. For the first time in history a serious attempt was made to use cannons in place of rockets to explore earth's upper atmosphere and to try to launch satellites.

Owens Valley 40-meter radio telescope begins operation, located in Big Pine, California.

American physicists Arno Penzias and Robert W. Wilson use a radio telescope to discover cosmic background radiation from the Big Bang.

Soviet astronaut Alexei Leonov makes the first space walk.

1966

Frank Low and Bruce J. Smith discover the first cocoon nebula.

Luna 9 makes the first soft landing on the Moon's surface.

Surveyor 1 makes a soft landing in the Ocean of Storms, on the Moon's surface.

Star Trek debuts on NBC.

Neil Armstrong and David Scott makes the first space docking in Gemini 8.

Luna IX probe lands on the Moon and Venera III makes a landing on Venus.

1967

• 1967 5 May: Ariel 3. Investigated astronomical objects in the radio range.

First VLBI images, with 183 km baseline.

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.

1968

• 4 July: Radio Astronomy Explorer (RAE) 1. Put in Earth orbit and deployed four 230-meter antennae; it discovered that Earth emits radio waves similar to Jupiter.
• 7 December: Apollo 8, carrying Frank Borman, James Lovell and William Anders, was the first to orbit the Moon see the dark side on December 8th.

Pulsars discovered by Anthony Hewish and Jocelyn Bell, very regularly pulsating radio stars identified as neutron star remnants of supernovas.

Thomas Gold demonstrated that charged particles inside the magnetic fields of neutron stars would produce radio radiation.

1969

16 July: Apollo 11 launched. Mission: To land the first man on the Moon