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Aristarchus (310–230 BC), a Greek astronomer and mathematician, designed a method to measure the distances to and sizes of the Sun and the Moon. Because he deduced that the Sun was so much bigger than the Moon, he concluded that the Earth must therefore revolve around the Sun.

Aristotle (384-322 BC), a Greek physician and philosopher, believed that the universe had never had a beginning and would never end, that it was eternal. In his treatise Meteorology, he describes meteors, comets, and the Milky Way as “atmospheric phenomena.” Although Aristotle's writings were based on first-hand observation, they were later used to impede observational science.

Johann Bode (1747-1826) was a German astronomer of the Academy of Science in Berlin from 1772 to 1825 and director of the Berlin Observatory from 1786. His most noted contribution to astronomy is the Uranographia (1801), a collection of star maps and a catalog of 17,240 stars and nebulae. In 1772, he devised a formula to express the relative distances of the Solar System planets from the Sun. This formula sometimes referred to as Titius' Law, the Titius-Bode Law, or Bode's Law.

Tycho Brahe, (1546-1601), a Danish astronomer working in Germany, made a remarkable star catalogue of over 1000 stars based on his significant improvements of methods and accuracy in observations. His wall quadrant and other instruments were widely copied and led to improved stellar instruments. Kepler used Tycho Brahe's observations when he constructed his famous laws of planetary movement.

Nicolas Copernicus (1473-1543) was born Mikolaj Kopernik. This Polish amateur astronomer and clergyman is said to be the founder of modern astronomy. After studying astronomy at the University of Kraków, he spent a number of years in Italy studying various subjects, including medicine and canon law. Sometime around 1500, he lectured in Rome on mathematics and astronomy. In 1512, he settled in Frauenburg, East Prussia, where he had been nominated canon of the cathedral. There he performed his canonical duties and also practiced medicine. In 1530, Copernicus completed and gave to the world his great work De Revolutionibus Orbium Coelestium, which asserted that the Earth rotated on its axis once daily and traveled around the Sun once yearly. That treatise was not published until 1543, when Copernicus was on his deathbed. His beliefs concerning the universe came to be known as the Copernican system.

Louis Jacques Mandé Daguerre (1787-1851), French painter and physicist, invented the daguerreotype in 1839, which was the first practical process of photography using silver on a copper plate.

Galileo Galilei (1564-1642), a scientist, author, and astronomer, discovered the satellites of Jupiter, the rings of Saturn, the changing shape of Venus, sunspots and solar rotation. His Juvenilia, dating from 1584, was mostly paraphrases of Aristotelian physics and cosmology. Galileo's rising reputation as a mathematician and natural philosopher (physicist) gained him a teaching post at the University of Pisa in 1589 and in 1592 at the University of Padua in the Venetian Republic. In 1604, Galileo publicly declared that he was a Copernican. Galileo succeeded in making a workable and sufficiently powerful telescope with a magnifying power of about 40. He turned the telescope toward the sky sometime in the fall of 1609, and within a few months, he gathered astonishing evidence about mountains on the Moon, about moons circling Jupiter, and about an incredibly large number of stars, especially in the belt of the Milky Way.

Annibale de Gasparis (1819 –1892) was an Italian astronomer. His first asteroid discovery was 10 Hygeia in 1849. Between 1850 and 1865, he discovered eight more asteroids. From 1864–1889, he was the director of the Capo di Monte Observatory in Naples. He won the Gold Medal of the Royal Astronomical Society in 1851. The lunar crater de Gasparis with a 30-kilometer diameter is named in his honor, as well as the Rimae de Gasparis, a 93-kilometer long fracture near the crater, and asteroid 4279.

Carl Friedrich Gauss (1777-1855) was a German mathematician, a giant among mathematical giants. As a young man, he made fundamental contributions to number theory, for which he invented the theory of congruences, a basic tool to this day. His theorems on line and surface integrals lie at the heart of modern physics and are essential for understanding electromagnetism. Gauss was one of the discoverers of non-Euclidean geometry. He conducted experiments to determine whether space was flat, negatively curved, or positively curved by accurately surveying a large triangle with vertices at three mountain tops, then seeing whether the sum of the interior angles is equal to zero, less than zero, or greater than zero. He found space to be flat, within the limits of experimental error. Gauss developed many computational tools and applied them to computing the orbits of planets and moons.

Tom Gehrels (1925- ), Dutch-American astronomer, was involved in the Palomar-Leiden Survey, observing smaller areas of the sky and making brightness and distance measurements of some 1,800 asteroids. In 1971, Gehrels edited the first text on asteroids and organized the first asteroid conference in Tucson, Arizona. He was the founder and General Editor of the Space Science Series of the University of Arizona Press. He helped to set up Spacewatch, a project at the University of Arizona that specializes in the study of minor planets, including various types of asteroids and comets. Dr. Gehrels and his colleagues observe with the 0.9-meter and 1.8- meter Spacewatch telescopes on Kitt Peak, which detect mostly main belt asteroids but also near-Earth asteroids. Spacewatch discovered a moon of Jupiter, now named Callirrhoe, which was originally mistaken for an asteroid, and recovered 719 Albert (a long-lost asteroid).

Hermann Goldschmidt (1802-1866), was a German painter and amateur astronomer who lived and worked above the Café Procope in Paris, France. He discovered 48 Doris and 49 Pales on the same night, September 17, 1857. By May 5, 1861, he had identified 14 new asteroids. He won the Gold Medal of the Royal Astronomical Society in 1861. A crater on the Moon is named after him as well as asteroid 1614 Goldschmidt.

Andrew Graham (1815-1907), professional astronomer and assistant to Edward Cooper at Markree Castle Observatory in Ireland, discovered 9 Metis on the night of April 25, 1848. He used a 4-inch (10-cm) Comet Seeker and an observing plan laid out by Cooper. It is said that Cooper was too busy to observe that evening, and on the asteroid’s discovery, delegated to Graham the choice of a name. Metis was the only asteroid found from an Irish observatory. Andrew Graham was born in 1815 in County Fermanagh, Northern Ireland. He was trained to the use of a meridian circle at Armagh Observatory, although there is no record of him being on the staff. He resigned his post at Markree in 1860 but continued his research at Cambridge Observatory until his retirement in 1905. He died at Cambridge in 1907.

David Gregory (1659-1708) started his university studies at the age of 12 at Marischal College, part of the University of Aberdeen. At the age of 24, he was appointed professor of mathematics at the University of Edinburgh, where he taught Newtonian theories. He was the first university teacher to teach the 'modern' theories at a time when even Cambridge was still teaching Greek natural philosophy. In 1690, there was political and religious unrest in Scotland, and David decided to leave for England. In 1691, David was elected Savilian Professor at Oxford. Newton was a major influence in his appointment. In the same year he became Savilian Professor, he was elected to be a Fellow of the Royal Society. In 1702, he published Astronomiae Physicae et Geometricae Elementa, which was a popular account of Newton's theories. He also worked on optics publishing Catoptricae et Dioptricae Sphericae Elementa in 1695. This work describes telescopes, a special interest of his. He also experimented with making an achromatic telescope.

Karl Ludwig Harding (1764-1834) was a German astronomer, notable for having discovered the asteroid 3 Juno on September 1, 1804. He was hired in 1796 by Johann Shröeter as a tutor for his son. It was in Shröeter’s observatory that he discovered Juno. He then went to Göttingen to assist Carl Friedrich Gauss. A crater on the Moon is named after him and so is the asteroid 2003 Harding.

Karl Hencke (1793-1866) was a postmaster and amateur astronomer in Driesen, Prussia. He discovered 5 Astraea and 6 Hebe in 1845. Hencke was looking for 4 Vesta when he found Astraea. The King of Prussia awarded him with an annual pension of $300 for the discovery. Since no asteroids had been discovered after Vesta, other astronomers had abandoned their searches for more asteroids, convinced that there were only four. Hencke began searching in 1830 and was successful fifteen years later.

Paul Herget (1908-1981) was Director of The Minor Planet Center at Cincinnati, Ohio, which was established as the International Astronomical Union Center for asteroid research in 1947.

Sir William Herschel (1738-1822) was born in Germany but lived most of his life in England. By 1773, Herschel had built a reflecting telescope with a focal length of 5.5 ft. In his search for double stars, he discovered that one star actually orbited around the other, the first tangible proof that gravity extended to stars. Out of this work came a first in its field, the Catalogue of Double Stars. In 1781, he discovered a new planet in the constellation of Gemini, the planet Uranus. One of Herschel's important discoveries was that the Sun is moving in space relative to its stellar neighbors. In an attempt to determine the structure of the Milky Way system, he used a technique called "star gauging." During a period 20 years ending in 1802, he had counted over 90,000 stars in 2400 sample areas.

John Russell Hind (1823-1895) was a British professional astronomer who began his career at the Royal Greenwich Observatory. As director of George Bishop’s private observatory, “South Villa” at Regents Park in London, England, he discovered 7 Iris and 8 Flora in 1847. From 1853 to 1891, he was Superintendent of the Nautical Almanac.

Edwin Powell Hubble (1889-1953), an American astronomer, was a pioneer in the study of extragalactic astronomy. In 1925, he devised a classification scheme for the structure of galaxies that is still in use today and provided the conclusive observational evidence for the expansion of the universe. Hubble obtained a law degree at Oxford and briefly practiced law before earning his Ph.D. in astronomy at Chicago in 1917. After World War I, Hubble went to Mount Wilson Observatory, where in 1923 he demonstrated that the Andromeda nebula was far outside our galaxy and established the island universe theory, which states that galaxies exist outside our own. In 1929 Hubble's study of the distribution of galaxies resulted in the discovery of Hubble's Law, from which the fundamental cosmological quantity is derived.

Johannes Kepler (1571-1631), astronomer and mathematician, studied at Tübingen and became a professor of mathematics at the Protestant seminary in Graz in 1594. Sometime during 1596, he started a correspondence with Tycho Brahe, who was then in Prague. In 1597, Kepler published his first important work, Misterium Cosmographicum (“The Cosmographic Mystery”). It contained his mathematical model designed to explain the relative distances of the planets from the Sun in the Copernican system. He announced his first and second laws of planetary motion in his 1609 publication Astronomia Nova (New Astronomy), which formed the groundwork of Isaac Newton's discoveries. It was in this publication that he predicted that there should be a planet between Mars and Jupiter. His third law was promulgated in Harmonice Mundi (1619, Harmony of the World). He succeeded Brahe as court astronomer to Emperor Rudolf II, and in 1628 became astrologer to Albrecht von Wallenstein at Zagan in Silesia.

Gerard Kuiper (1905-1973), American astronomer born in the Netherlands, worked in the McDonald Observatory in Texas. From 1950 to 1952, he conducted an asteroid survey using a 10-inch telescope that recorded asteroids down to a magnitude of 16.5 and photographed the entire ecliptic twice. Kuiper is considered to be the father of modern planetary science for his wide ranging studies of the Solar System. In 1951, he proposed the existence of a disk-shaped region of minor planets outside the orbit of Neptune (now called the Kuiper Belt) as a source for short-period comets—those making complete orbits around the Sun in less than 200 years. During the 1960s, Kuiper served as chief scientist for the Ranger lunar-probe program, choosing crash-landing sites on the Moon. By analyzing Ranger photographs, he helped to identify sites for the Surveyor and Apollo programs. A pioneer in the development of infrared astronomy, he was honored posthumously when the National Aeronautics and Space Administration (NASA) named its airborne infrared telescope the Kuiper Airborne Observatory (1975). Kuiper was the editor of two encyclopedic works, The Solar System (4 vol., 1953-58) and Stars and Stellar Systems (9 vol., 1960-68).

Joseph Lalande (1732-1807), a French astronomer, was sent to Berlin by the French Academy to determine the Moon's parallax. From 1762, he was professor of Astronomy in the Collège de France and later became director of the Paris Observatory. His chief work is Traité d'astronomie (1764), and he also produced the most comprehensive star catalogue of his time (1801).

Hans Lippershey also spelled Lipperhey (1570 –1619), spectacle-maker in Holland, was born in Wesel (western Germany) and settled in Middelburg, the capital of Zeeland in the southwesternmost province of the Netherlands. New glass-making techniques were introduced here by Italians in the 1590s, and perhaps some ideas about combining lenses were abroad in this glass-making community. Lippershey is believed to be the first to apply for a patent for his design of an early telescope in 1608. Although the patent was eventually denied because it was felt that the device could not be kept a secret, Lippershey made several binocular telescopes for the States General and was paid handsomely for his services. The surviving records are not sufficient to decide who was the actual inventor of the telescope, but Lippershey's patent application is the earliest record of an actually existing telescope.

Theodore Robert Luther (1822-1900), professional astronomer at the Municipal Observatory in Düesseldorf, Germany, discovered 17 Thetis in 1852. By February 20, 1890, he had discovered 24 asteroids.

Michael Maestlin (1550-1631), German pastor and mathematician, attended mathematics and astronomy lectures given by Peter Apian, a professor of mathematics, while studying at Tuebingen. Enrolled in a theological course, he served as an assistant to Professor Apian. In 1580, after serving in a pastorate, he was appointed professor of mathematics at the University of Heidelberg. From 1584-1631, he served as professor of mathematics at the University of Tuebingen. He was Kepler’s mathematics teacher and later corresponded with him. He was an amateur astronomer who made most of his own astronomical instruments.

Jacob Metius (1571-1635) invented a device for "seeing faraway things as though nearby." He also applied to the States General in the Netherlands for a patent on his telescope and was denied.

Sir Isaac Newton (1643-1727), one of the most important figures in the history of science, made significant contributions in the fields of physics, astronomy, and mathematics. In his Principia (1687), considered by many the greatest work of modern science, he explained the laws of motion and universal gravitation. Newton's discoveries in optics were presented in his Opticks (1704), in which he elaborated his theory that light is composed of corpuscles, or particles. These discoveries led Newton to the logical but erroneous conclusion that telescopes using refracting lenses could never overcome the distortions of chromatic dispersion. He, therefore, proposed and constructed a reflecting telescope in 1668, the first of its kind, and the prototype of the largest modern optical telescopes.

Heinrich Wilhelm Matthäus Olbers (1758–1840) was a German astronomer and physician. In 1797, he originated the first satisfactory method for calculating the orbits of comets, but despite the fame it brought him, he remained an amateur astronomer and became a physician. He continued his research on comets and discovered several. He was the first to detect the comet of 1815 (Comet Olbers). He also discovered two asteroids, Pallas (1802) and Vesta (1807). Considering their orbits and those of the other asteroids then known, Olbers concluded that they were fragments of a disrupted planet that had formerly revolved around the Sun. He is best remembered for Olbers' paradox: “Why is the sky dark at night?” Assuming that space was infinite and filled with stars, he suggested the entire sky should be as bright as the surface of the Sun. The question had originally been raised by Kepler. The correct explanation is that our universe is finite both in time and place, and the total amount of matter and energy is far too small to light up the night sky.

Johann Palisa (1848-1925) was an Austrian astronomer. He was a prolific discoverer of asteroids. Between 1874 and 1923, Palisa discovered a total of 122 asteroids—28 of them at the Pola Marine Observatory and the rest at the Vienna Observatory.

Christian Heinrich Friedrich Peters (1813-1890), born in Denmark, was a professional astronomer who studied under Carl Friedrich Gauss. He went to the United States in 1854, where he worked at Hamilton College in Clinton, New York. He was a prolific discoverer of asteroids. He found both 144 Vibilia and 145 Adeona on June 3, 1875. In two decades of searching, he found a total of 48 asteroids.

Giuseppe Piazzi (1746-1826), an Italian monk and amateur astronomer, discovered Ceres on January 1, 1801, from his observatory on the island of Sicily. He became a Theatine monk, professor of theology in Rome in 1779, and professor of mathematics at the Academy of Palermo in 1780. He supervised construction of a government observatory, which opened in 1791 at Palermo, and was its first director. In 1817, he also established a government observatory at Naples. In 1803, he published a catalog of the fixed stars, and in 1814, he enlarged it to include 7,646 stars. He wrote Lezioni Elementari di Astronomia in 1817.

Claudius Ptolemaeus (also known as Ptolemy) (c.87-c.165AD) was a celebrated Greco-Egyptian mathematician, astronomer, and geographer. He made his observations in Alexandria and was the last great astronomer of ancient times. Although he discovered the irregularity in the Moon's motion and made original observations regarding the motions of the planets, his place in the history of science is that of collator and expounder. He systematized and recorded the data and doctrines that were known to Alexandrian men of science. His works on astronomy and geography were the standard textbooks until the teachings of Copernicus came to be accepted. The Ptolemaic system represented the Earth (a globe in form) as stationary in the center of the universe, with Sun, Moon, and stars revolving about it in circular orbits and at a uniform rate. From the center outward the elements were earth, water, air, fire, and ether. Beyond lay zones or heavens, each an immense sphere. The planets were assumed to revolve in small circles, called epicycles, whose centers revolved around the Earth in the vast circles or deferents of the spheres. To account for the precession of the equinoxes and other phenomena, later astronomers found it necessary to add more epicycles and to make both epicycles and deferents eccentric.

Pythagoras (c.582–c.507 BC), was a pre-Socratic Greek philosopher and founder of the Pythagorean school. He migrated from his native Samos to Crotona and established a secret religious society or order similar to, and possibly influenced by, the earlier Orphic cult. We know little of his life and nothing of his writings. Since his disciples came to worship him as a demigod and to attribute all the doctrines of their order to its founder, it is virtually impossible to distinguish his teachings from those of his followers. The Pythagoreans were influential mathematicians and geometricians, and the theorem that bears their name is witness to their influence on the initial part of Euclidian geometry. They made important contributions to medicine and astronomy and were among the first to teach that the Earth was a spherical planet, revolving about a fixed point.

George Rheticus (1514-1574), a German mathematics professor, was born Georg Joachim von Lauchen Rheticus. He studied mathematics at Zürich. At 25 years of age, he read one of the Copernicus papers and sought to study under him. Intending to spend a few weeks with Copernicus, Rheticus ended up staying as a house guest for two years, He became Copernicus's only student and spokesman. He published a popularization of Copernicus's theories entitled Narratio Prima in 1540. He also managed to convince Copernicus shortly before his death to allow publication of De Revolutionibus Orbium Coelestium. Unfortunately, he left publication in the hands of Lutheran minister Andreas Osiander, who did not believe that Copernicus's theory represented a physical model. He added an unauthorized preface stating that the contents were merely a device to simplify calculations.

Eugene M. Shoemaker (1928-1997) was a geologist who influenced decades of research on the role of asteroids. It was shortly after 1969, when he arrived at California Institute of Technology in Pasadena, that he became interested in extending his geological knowledge of the formation and distribution of terrestrial and lunar impact craters to the study of the astronomical objects that formed them. With Eleanor Helin, he developed a plan to search for the Apollo asteroids with the 0.46-m Schmidt telescope at Palomar. This search program had its first success in July 1973 and was soon, with the help of a number of students and of collaborations using other Schmidt telescopes, significantly augmenting the rather meager knowledge that had been accrued on these objects during the previous four decades. By the time the observing program ended, in late 1994, it had produced 40 of the now 417 known Amor, Apollo, and Aten asteroids (the orbits of this last group being smaller than that of the earth).

Johan Schröeter (1745-1815), a German astronomer with a private observatory at Lilienthal, Germany, was elected president of the Societas Lilientalica. In 1777, he was appointed Secretary of the Royal Chamber of George III in Hanover, where he met two of William Herschel’s brothers. Herschel’s discovery of Uranus inspired Schroeter to pursue astronomy more seriously, and he resigned his post and became Chief Magistrate of Lilienthal. He acquired two telescopes made by Herschel and concentrated almost entirely on observations of the Moon.

Johann Daniel Titius (1729-1696) was a German astronomer and professor at Wittenberg. He is best known for formulating the Titius-Bode Law, which is the observation that orbits of planets in the Solar System closely follow a simple geometric rule. It was discovered in 1766 and “published” (without attribution) in 1772 by Johan Elert Bode. Some say, however, that Christian Wolff first proposed it in 1724. The asteroid 1998 Titius is named in his honor.

James Watson (1838-1880), a Canadian-American astronomer, was the director of the University of Michigan Detroit Observatory in Ann Arbor, Michigan from 1863-1879. He wrote the textbook Theoretical Astronomy in 1868. He discovered 22 asteroids, including the 100th asteroid in 1868. One of his asteroid discoveries, 139 Juewa, was made in Beijing in 1874 when Watson was there to observe the transit of Venus.

Max Wolf (1863-1932) was a German astronomer and a pioneer of astrophotography.
He worked in Heidelberg, where he discovered more the 200 asteroids, beginning with 323 Brucia in 1891. His astrophotographic techniques automated the discovery of asteroids, which sharply increased discovery rates over the older visual methods. In time-exposure photographs, asteroids appear as short streaks due to the planetary motion with respect to fixed stars.

Baron Francis Xaver von Zach (1754-1832), astronomer and geodesist, was born in Pest. He was patronized by Duke Ernst of Saxe-Gotha-Altenburg and built an observatory on the Seeberg near Gotha. He directed the observatory—one of the most important of the time—from 1791, when it was completed, until 1806. During this period, Zach enlisted 24 astronomers throughout Europe in making a systematic search for asteroids. They came to be called the Celestial Police. He also published the Monthly Correspondene.