The following identifies some of the notable astronomers who helped to define the field of Astronomy as we know it today.  A brief summary of the contributions of some of the more important astronomers is given.  Others are just listed in the Century that they contributed.  Please select one or two of those listed and Google their name to learn of the specific contribution they made.

Note that it has only been in the last 500 years that man has really begun to understand the  universe.  It was not until Copernicus that we discovered  that the Earth, as well as the other planets, revolved around the Sun.  Of course, the advent of the telescope and subsequent inventions enabled these early explorers to extend their knowledge beyond our primary senses.  Although we have only just scratched the surface of this fascinating subject, the Astronomers listed here have provided a solid foundation with which to continue the journey.  The discoveries they had made were well founded and proven many times over in the years since.

Early Astronomers – Discoveries of the Solar System

The Greeks were the first to observe and predict the movements of the “stars”. It was known that certain star formations occurred at specific times during the year and the prediction of these events was very important.  It was the sole objective of astronomers in ancient times. They noted that a few of the objects moved independently of all the rest. These were called “wanderers” because their movement was difficult to predict. We now know these objects to be the planets. The Greeks thought of the night sky as a sphere with all the stars attached to it. The movement of the wanderers was accounted for by placing them in individual circular orbits around the Earth, this included the Sun and Moon. The resultant model of the universe became very complex with regard to the movement of the planets. Of course we now recognize the major flaw with the Greek idea of the universe was this notion that all the objects in the night sky revolved around the Earth.

copernicus1Eventually Nicolaus Copernicus (1473-1543), a Polish astronomer and mathematician, developed the theory that the Sun, not the Earth, was the center of the universe. This was a major breakthrough since the motion of the planets could now be more direct and the movement easier to predict. In spite of this, Copernicus was forced by the Church to renounce his theory.

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It was not until Galilei Galileo (1564-1642) used the telescope to observe the heavens and was able to observe the phases of Venus and the shadows on the Moon that proof for a Sun-centered universe was finally discovered. Even so, his theory retained the idea of the planet orbits to be circles and this flaw continued to make prediction of the planet movements very difficult and inaccurate. Note also that the Church continued to denounce the idea of a sun-centered universe and silenced his defense of the Copernican theory.  It was not until 1992, more than 300 years later, that Pope John Paul admitted that the Church had made a mistake, but the reality is that religion would not be so easily influenced by science……and therein lies today’s divide between religion and science in matters regarding the beginning of the universe and, ultimately, the beginning of life.

 KeplerJohannes Kepler (1571-1630) spent considerable effort to resolve the problem of predicting the motion of the planets and, with his access to the observational data of Tyco, developed the theory of elliptical orbits for the planets. This allowed the accurate prediction of planetary motion and explained the odd observations of the planets at certain times of the year.

18th Century Astronomers – Solving problems

Around the time of the American Revolution, European Astronomers were beginning to discover and understand our solar system.  It all began with Newton’s theory of universal gravitation in 1666.

Isaac Newton (1642-1727) England John Flamsteed (1646-1719) England Edmund Halley (1656-1742) England Jacques Cassini (1677-1756) France James Bradley (1693-1762) England Thomas Wright (1711-1786) England Alexis Claude Clairaut (1713-1765) France Jean le Rond d’Alembert (1717-1783) France Immanuel Kant (1724-1804) Germany Henry Cavendish (1731-1810) England Joseph Lalande (1732-1807) France Nevil Maskelyne (1732-1811) England

19th Century Astronomers – what Stars are made of

Around the time of the American Civil War, European Astronomers were using the newly discovered Spectroscope to determine the composition of the sun and stars.

Joseph-Jerome de Lalande (1732-1807) France William Herschel (1738-1822) England Jean-Baptiste-Joseph Delambre (1749-1822) France Giuseppe Piazzi (1746-1826) Italy Pierre-Simon Laplace (1749-1827) France Heinrich Olbers (1758-1840) Germany William Hyde Wollaston (1766-1828) England Carl Friedrich Gauss (1777-1855) Germany Friedrich Wilhelm Bessel (1784-1846) Germany Joseph Fauenhofer (1787-1826) Germany John Friedrich William Herschel (1792-1871) England Friedrich Georg Wilhelm von Struve (1793-1864) Germany, Russia Karl Ludwig Henke (1793-1866) Germany Thomas Henderson (1798-1844) England Friedrich Wilhelm August Argelander (1799-1875) Germany George Biddell Airy (1801-1892) England John William Draper (1811-1882) England Urbain Jean Joseph Leverrier (1811-1877) France Robert W. Bunsen (1811-1899) Germany John Couch Adams (1819-1892) England Gustave Robert Kirchoff (1824-1887) Germany William Huggins (1824-1910) England Eduard Schonfeld (1828-1891) Germany Norman Robert Pogson (1829-1891) Johann Karl Friedrich Zollner (1834-1882) Germany Giovanni Virginio Schiaparelli (1835-1910) Italy

20th Century Astronomers – Peeking at Stars and Galaxies

New Physics and Chemistry advances.

George Ellery Hale (1868-1938) was the builder of large Telescopes and promoted the cooperation of Astronomers and Physicists. These two developments allowed the discovery of the concepts of how stars work. This in turn has given new understanding to the age of the universe. Hale is the father of three giant observatories: Yerkes, Mt. Wilson, and Palomar. He never saw Palomar completed.

Edwin Powell Hubble (1889-1953) discovered that other galaxies exist besides our own Milky Way. He studied the spiral nebulae. and determined them to be galaxies like our own, but outside the Milky Way.  He also made the important discovery of the red shift of the colors in the spectrum of the starlight from distant galaxies, indicating that the galaxies are moving apart from each other, and suggesting an expanding universe. Hubble developed an equation for determining the velocity of recession however the equation included a constant which was difficult to determine.  This constant was named after him…the Hubble Constant.  He made the first calculation for the value of the Hubble Constant, unfortunately, the value for the Hubble Constant was too large to be possible because it resulted in a velocity that was too great and the universe would be younger than the earth. Since then, the Hubble Constant has been recalculated and confirms the universe is expanding slow enough to be very old.

George Gamow ( 1904-1968) was Russian born and developed the Big Bang theory. The Big Bang Theory is the leading theory today for the beginning of the universe…. as we know it.   However he was off the mark on his theory that all the elements were created in the Big Bang, although 99% of the matter in the universe (hydrogen and helium) was created in the first 20 minutes after the Big Bang.  Also, his theory predicted that the background radiation left over from the Big Bang should be detectable today but his mathematics was in error and he calculated this radiation to be about 50° above absolute zero. Actually it is less than 5° above absolute zero.

Joseph Norman Lockyer (1836-1920) England Jacobus Cornelius Kapteyn (1851-1922) Netherlands Henrietta Swan Leavitt (1868-1921) U.S. Willem de Sitter (1872-1934) Netherlands Heber Doust Curtis (1872-1942) U.S. Ejnar Hertzsprung (1873-1967) Denmark Vesto Melvin Slipher (1875-1969) U.S. Henry Norris Russell (1877-1957) U.S. Arthur Stanley Eddington (1882-1944) England Adriaan van Maanen (1884-1946) Netherlands Harlow Shapley (1885-1972) U.S. Walter Baade (1893-1960) Germany Georges F. Lemaitre (1894-1966) France Fritz Zwicky (1898-1974) Bulgaria Jan Hendrik Oort (1900-1992) Netherlands Karl Janksy (1905-1950) U.S. Hans Bethe (1906- ) France, U.S. Carl von Weizsacker (1912- ) Germany Herman Bondi (1919- ) Austria Thomas Gold (1920- ) Austria Fred Hoyle (1915- ) England Arno Penzias (1933- ) U.S. Robert Wilson (1936- ) U.S.