50 Famous Astronomers You Should Know (Ancient to Modern)

The history of famous astronomers is really a history of the development of human civilization.

About 200,000 years ago, the first of our species evolved but it is only in the past few thousand years that we have been able to record history and make huge technological leaps.

The first astronomers were the first people to look up and wonder about what these objects in the sky were and what our place in the universe was. We do not know what civilization was the first to do this and there is evidence of humans tracking the phases of the moon that goes as far back as 35,000 B.C.

So, while they may not have been the first, the ancient Greeks gave us our first famous astronomers and this is the starting point for our list here with famous names like Aristotle and Pythagoras.

We then see the fall of Rome and the advent of the Dark Ages in Europe – a period of slower development and few records. But we then see the advent of the medieval Middle East, where the Arabic and the Persian world under Islam had become highly civilized and notable individuals made contributions to the development of astronomy.

We are then taken to the Renaissance in Europe and real advances from the likes of Copernicus and Galileo and the advancement of scientific reason over religious and supernatural thought.

We then have thinkers such as Newton and Einstein making huge leaps and from then we see the rapid technological advancement of tools and astrophysical theories up to modern-day thinkers such as Stephen Hawking.

The people listed here have all made important contributions to the development of astronomy but this list is by no means exhaustive and many more could be added. It is ordered by year of birth.

Famous astronomers of the classical period: 600 BC to the 1st Century AD – the ancient Greeks and Romans

Thales of Miletus (624-547 B.C., Greek)

• One of the Seven Sages of Greece and recognized for being the first to advocate scientific thought – i.e. moving beyond mythology to instead explaining natural objects and phenomena through theories and hypotheses.
• He predicted the solar eclipse of May 28, 585 BC, described the position of Ursa Minor and thought the constellation might be useful as a guide for navigation at sea. He calculated the duration of the year and the timings of the equinoxes and solstices.
• The Greek fable The Astrologer who Fell into a Well is a story revolving around Thales falling into a well whilst looking at the stars. This is meant to teach a lesson about focusing on what’s far away might result in something closer tripping you up.

Anaximander (611-547 B.C., Greek)

• A student of Thales and another early proponent of scientific analysis of the universe. Anaximander was the first astronomer to consider the Sun as a huge mass and to estimate its distance from Earth.
• He made the first detailed maps of the Earth and the sky and knew that the Earth was round and that it was free-floating and unsupported. He measured its circumference and was the first to put forward the idea that celestial bodies make full circles in their orbits.

Pythagoras (569-475 B.C., Greek)

• A mathematician whose theorem is taught in high-school mathematics to this day.
• The Pythagorean astronomical system was the first to propose that the planets and stars move in circles, although he theorized that our Earth and Sun orbited an as-yet-unseen “Central Fire”.

Philolaus (470-385 B.C., Greek)

• The successor to Pythagoras advanced the “Central Fire” theory that the Earth was not from the center of the universe and was, in fact, a planet.

Aristotle (384-322 B.C., Greek)

• The student of Plato and teacher of Alexander the Great. He proved that the Earth was spherical by noting that the shadow of the earth on the moon during a lunar eclipse was always circular and that the only shape that always casts a circular shadow is a sphere. He also noted that as one traveled more north or south, the positions of the stars in the sky change.
• He believed that Earth was at the center of the universe with the Sun, planets, and stars revolving around it and that the Earth didn’t move – a misunderstanding that was not corrected until the time of Galileo.

Anaxagoras (510–428 B.C., Greek)

• Advanced the theory that the stars were distant bodies like the Sun.

Aristarchus of Samos (310-230 B.C., Greek)

• Developed the first heliocentric model – the idea that the Sun was in the center of a system with the Earth and other planets revolving around it. This idea was too radical at the time and it wasn’t until 1750 years later that it was fully accepted and advanced by Copernicus (who attributed it to Aristarchus).
• He was the first to predict the rotation of the earth on its axis and also tried calculating the distance between the earth and the moon. His calculations were incorrect but later astronomers used his data and methods to arrive at more accurate calculations.

Hipparchus (190-120 B.C., Greek)

• Hipparchus was the founder of trigonometry and is viewed as a founding father of astronomy having put together the first known star catalog to organize 850 astronomical objects (which was later used extensively by Ptolemy).
• He created a system for predicting solar eclipses and studied them to help determine the distance from the Earth to the Moon. He very nearly correctly measured the distance to be 29.5 Earth diameters (today we know it is 30 Earth diameters).
• He discovered the wobble of the Earth’s axis caused by the gravitational pull of the Sun and Moon and also created a method by which a star’s brightness is measured – a version of this magnitude system is still used today.

Claudius Ptolemy (100-170 A.D., Egyptian-Greek-Roman)

• An astronomer who used Hipparchus’ extensive observations to develop a model that predicted the movements of the Sun, Moon, planets, and stars. His model, called the Ptolemaic system, visualized an Earth-centered universe and assumed that all astronomical objects move at constant speeds in circular orbits. The Ptolemaic model is one of the longest upheld scientific theories in history and it was the cornerstone of astronomy for 1,500 years.
• He was the last great astronomer before the known world’s descent into the Dark Ages. He preserved Hipparchus’ star catalog by including it in his Amalgest – the most important astronomical text for close to fifteen hundred years.
• He also included in his work a set of tables that made it easier to calculate the positions of the planets, the sun and the moon, the rising and setting of the stars, and the dates of lunar and solar eclipses. Without Ptolemy’s preservation of Hipparchus’ work and his own advances in the field of astronomy, much of the astronomical work done during the Renaissance and the Scientific Revolution may not have been possible.

Famous astronomers of the 5th to 13th Centuries: The age of Asian and Middle-Eastern astronomers

With the fall of the Roman Empire and the advent of the Dark Ages in Europe for the next 1,500 years, it is the medieval Middle East that provides advancements in astronomy.

Aryabhata (476-550, Indian)

• The first of the major mathematician-astronomers from the Indian classical age.
• One of the first astronomers to theorize that the earth was round. He also believed that it rotated on its own axis and this was the reason for night and day. Correctly believed the moon was illuminated by the sun.

Muḥammad ibn Mūsā al-Khwārizmī (780-850, Persian)

• The inventor of algebra. Al-Khwarizmi performed detailed calculations of the positions of the Sun, Moon, and planets, and did a number of eclipse calculations. He constructed a table of the latitudes and longitudes of 2,402 cities and landmarks, forming the basis of an early world map.
• His work – the Zīj al-Sindhind – contained around 37 chapters on calendrical and astronomical calculations and 116 tables with astronomical and astrological data. The original Arabic version (written in the year 820) is lost, but a Latin translation by the Spanish astronomer Maslamah Ibn Ahmad al-Majriti survived.

Al-Kindi (801-873, Islamic)

• Wrote more than 15 books on the topic of astronomy and was influenced by Ptolemy and Aristotle. Believed the Earth was the center of the universe but theorized that the circular orbit of the planets was their divine obedience to God.

Maslamah Ibn Ahmad al-Majriti (950-1007, Spanish)

• Spanish astronomer who translated Al-Khwārizmī’s work on astronomy into Latin and accordingly it survived to today where the original Arabic version was lost.

Omar Khayyam (1048-1131, Persian)

• Calculated the solar year as 365.24219858156 days (correct to six decimal places) and performed a reformation of the calendar.
• Also compiled astronomical tables and is thought to have demonstrated a Heliocentric theory that the universe was not moving around Earth.

Bhaskara (1114-1185, Indian)

• Bhaskara wrote Siddhanta Shiromani, a book that explored the planets and earth.
• He accurately defined many astronomical quantities and estimated the time for the earth to travel around the sun.

Nasir al-Din al-Tusi (1201-1274, Persian)

• Theorized that the Milky Way was made up of many tight clusters of faint stars which gave the galaxy its “milky” appearance. Three centuries later the proof of this came when Galileo used a telescope to study the Milky Way and discovered that it is really composed of a huge number of tightly clustered stars.
• Created a planetary movement model that advanced Ptolemy’s theories in this area.

Famous astronomers of the 16th to 19th Centuries

The time of the Renaissance in Europe sees the start of a period of great advancements in rational scientific thought over religious belief.

Nicolaus Copernicus (1473-1543, Polish)

• Began a new era of astronomy when he concluded that the Sun was the center of the universe instead of the Earth. Although some ancient astronomers had pondered a Heliocentric theory, their works had either been lost to the ages or largely ignored. However, in 1543 when his book, On the Revolutions of the Celestial Spheres, was published, the theory could simply not be brushed aside any longer.
• The revolutionary idea was not popular with the Church, but with several other astronomers such as Brahe and Galileo he helped to eventually prove that this model of the universe portrayed reality.

Tycho Brahe (1546-1601, Danish)

• Created the Tychonic system – a model of the universe which combined ideas from Copernicus and the geocentric model and made the most precise observations of stellar and planetary positions then known. He was one of the last astronomers to use the naked eye for making observations rather than a telescope.
• He built an observatory from which he made the most accurate astronomical observations up to that time. His observatory contained sophisticated equipment for mapping star positions, and for more than 20 years he made detailed records of his findings.
• He cataloged hundreds of objects and in 1572, he observed a bright star that appeared to be a newcomer onto the celestial scene and was, therefore, the first to scientifically observe and acknowledge a supernova –  now known as ”Tycho’s supernova”.

Galileo Galilei (1564-1642, Italian)

• Known as the “Father of Observational Astronomy”, he was among the first to use a telescope to observe the sky after hearing about its invention in the Netherlands. He constructed a 20x refractor telescope himself in 1609 and he was able to make a number of major discoveries which changed the face of astronomy.
• He discovered mountains and craters on the moon, the phases of Venus (still called the “Galilean Moons” today), and the four largest satellites of Jupiter: Io, Europa, Callisto, and Ganymede –  the first observation of satellites orbiting another planet. He was the first to lay eyes on the Rings of Saturn and observed and provided an analysis of sunspots.
• He advanced the theory of heliocentrism during a time when the Earth was still considered to be at the center of the universe. He publicized the fact that other astronomical bodies, such as Jupiter’s moons, were clearly revolving around something other than the Earth. The Church responded to Galileo’s support of the Copernican model of the universe by putting him on trial in 1633, forcing him to renounce his views and holding him under house arrest to live out the last eight years of his life in his villa near Florence.

Johannes Kepler (1571-1630, German)

• Kepler was the first to fully explain the laws of planetary motion – which came to be known as Kepler’s Laws.
• He made a breakthrough by proposing elliptical, rather than circular, orbits of planets, was the first to explain how the moon influenced tides and also established the most exact astronomical tables then known.
• Like Copernicus and Galileo, he believed in a heliocentric solar system and championed the idea of bringing it to the forefront of the scientific revolution of the 17th Century.

Giovanni Battista Riccioli (1598-1671, Italian)

• Made telescopic lunar studies and published detailed lunar maps in which he coined nomenclature for lunar objects. Also discovered the first double star (Mizar).

Giovanni Domenico Cassini (1625-1712, Italian-French)

• Cassini was the astronomer who first discovered the division in the rings of Saturn, today known as “Cassini’s division”. He also discovered four satellite moons orbiting Saturn and measured the periods of rotation of Jupiter and Mars.
• The Cassini space mission currently on its way to Saturn is named after him.

Christiaan Huygens (1629-1695, Dutch)

• Using a telescope that he designed, Huygens observed the ring of Saturn and its elliptical shape. He also discovered Saturn’s first satellite, Titan, and was the first to observe the Orion Nebula, in the Orion constellation.
• In his last book, Cosmotheoros, he suggested the possibility of extraterrestrial life on other planets.

Sir Isaac Newton (1643-1727, English)

• Widely recognized as one of the most influential scientists of all time. Newton’s book Principia formulated the laws of motion and universal gravitation that dominated scientists view of the physical universe for the next three centuries.
• Newton removed the last doubts about the validity of the heliocentric model of the Solar System and demonstrated that the motion of objects on Earth and of celestial bodies could be accounted for by the same principles. He also built the first reflecting telescope.

Edmond Halley (1656-1742, English)

• Halley became famous for predicting the 1682 appearance of a comet – which became known as Halley’s Comet. He proved that the orbit of comets is periodic and also explained how comets have an elliptical orbit around the sun.

Charles Messier (1730-1817, French)

• Messier was a comet hunter who discovered 19 comets. His search for comets led him to create one of the most famous catalogs of 110 deep sky objects. He believed that these objects could distract other comet-chasers and so he cataloged them – being the first to do so for many galaxies, nebulae, and clusters of stars. The Messier Astronomical Catalog organized many objects in a system still used by astronomers today.

Joseph-Louis Lagrange (1736-1813, Italian-French)

• Lagrange made many theoretical contributions to astronomy and worked to solve several questions, including why one side of the moon always showed towards the Earth and how to determine the orbit of a comet.
• He improved our understanding of lunar motion and the perturbing effects of planets on cometary orbits. He also found the solution to the general 3-body problem showing there could be two points (now called Lagrange points) in orbit of Jupiter where minor planets could stay almost indefinitely – the Trojan group of asteroids were later discovered at these positions.

William Herschel (1738-1822, German-English)

• Herschel discovered Uranus and its two brightest moons, Titania and Oberon. He also discovered two of Saturn’s moons, Mimas and Enceladus, discovered the ice caps of Mars, several asteroids, and binary stars, cataloged 2,500 deep-sky objects and was the first to realize that the solar system was moving through space (and estimated the direction of the movement).
• He also accidentally discovered infrared radiation when using filters during observation of sunspots. While experimenting with dividing light through a prism, he measured the temperature of the air next to the red in the rainbow of light produced. Where he expected a lower reading than that of the visible light, he saw a spike on the thermometer and deduced that there must be some sort of invisible radiation just outside that of the color red – infrared radiation.
• He built his own reflecting telescopes to observe binary systems of stars, in which two stars orbit around a common center of gravity in a bound system. These were important star systems because many believed that distances to them could be more easily discovered than single star systems. He is credited with discovering over eight hundred of these binary systems.

Giuseppe Piazzi (1746-1826, Italian)

• Piazzi accurately measured the positions of many stars, resulting in the Palermo Catalogue containing 7,646 stars and discovered the first dwarf planet, Ceres.
• https://en.wikipedia.org/wiki/Giuseppe_Piazzi

Johann Elert Bode (1747-1826, German)

• Published what is now known as Bode’s Law, which predicted the distances of the planets from the Sun. Using his law, he predicted an undiscovered planet between Mars and Jupiter, where the asteroid belt was later found.

Pierre-Simon Laplace (1749-1827, French)

• LaPlace is one of the first astronomers to suggest the existence of black holes in space. He also presented a theory to explain the origin of the solar system, the nebular hypothesis.

Caroline Herschel (1750-1848, German)

• The first woman to discover a comet and discovered five in total. One of these was named after her – the 35P Herschel-Rigollet Comet.
• She worked with her brother William on astronomical observations and was awarded the Gold Medal by the Royal Astronomical Society in 1828.

Heinrich Wilhelm Matthias Olbers (1758-1840, German)

• Olbers invented the first successful method for calculating cometary orbits. He discovered several comets, including one now called Olber’s comet and also discovered the asteroids Pallas and Vesta. He also posed Olber’s Paradox: “Why is the night sky dark?”.

Friedrich Bessel (1784-1846, Prussian)

• Bessel was the first to measure the distance to the star 61 Cygni, proposed that Sirius has an unseen companion and worked out the mathematical analysis of what is now known as “Bessel functions”.

Joseph von Fraunhofer (1787-1826, German)

• Von Fraunhofer discovered dark lines in the spectrum coming from the Sun (now known as Fraunhofer lines). He carefully measured the positions of over 300 of these lines, creating a wavelength standard that is still in use today.

Johann Franz Encke (1791-1865, German)

• Encke discovered the first short-period comet, now called Encke’s comet.
• He also described a broad variation in the brightness of the ‘A Ring’ of Saturn. The Encke Gap was later named in honor of his observations of Saturn’s rings.

Friedrich Georg Wilhelm von Struve (1793-1864, German-Russian)

• Struve is best known for his observations of double stars (a pair of stars that appear close to each other when viewed through a telescope) and published a catalog of 3000 of these. He was also the first to measure the distance to the star Vega.

Wilhelm Beer (1797-1850, Prussian)

• Beer produced the first exact maps of the Moon and Mars and accurately calculated Mars’s rotation period

Thomas Henderson (1798-1844, Scottish)

• The first person to measure the distance to a star (Alpha Centauri).

William Lassell (1799-1880, British)

• Lassell discovered Triton, the largest satellite of Neptune. He also pioneered the use of an equatorial mount as part of a telescope for the tracking of objects as the Earth rotates.

George Biddell Airy (1801-1892, British)

• Studied planetary orbits and measured the mean density of the Earth. In his role as Astronomer Royal in the UK, he established Greenwich as the location of the prime meridian.

Urbain Le Verrier (1811-1877, French)

• Le Verrier accurately predicted the existence and position of Neptune using only mathematics. He sent his calculations to Johann Gottfried Galle who then found Neptune the day he received the calculations. This was a validation of celestial mechanics (applying the principles of physics to astronomical objects).

Anders Jonas Ångström (1814-1874, Swedish)

• Proved that the Sun’s atmosphere contains hydrogen and produced a map of the normal solar spectrum including detailed measurements of more than 1000 spectral lines.
• The first to examine the spectrum of the aurora borealis (“The Northern Lights”).

Daniel Kirkwood (1814-1895, American)

• Kirkwood noted the gaps in the orbits of the asteroids between Mars and Jupiter – which are now named “Kirkwood gaps”.
• Also identified a pattern relating the distances of the planets to their rotation periods, which was to be called “Kirkwood’s Law”.

Henry Draper (1837-1882, American)

• Draper was a pioneer of astrophotography and made the first photograph of a stellar spectrum. He later photographed spectra of over a hundred stars and published them in a catalog.
• In studying the spectrum of Orion Nebula he showed it was a dust cloud.

Famous astronomers of the 20th Century

Johann Gottfried Galle (1812-1910, German)

• Galle was the first astronomer to observe Neptune – after being sent calculations by Urbain Le Verrier who had predicted its existence using mathematics.
• Discovered a dark ring of Saturn and three previously undiscovered comets.

William Huggins (1824-1910, British)

• Huggins was the first to take the spectrum of a planetary nebula and the first to distinguish between nebulae and galaxies by showing that some (like the Orion Nebula) had pure emission spectra characteristic of gas, while others (like the Andromeda Galaxy) had the spectral characteristics of stars.

Sir Joseph Norman Lockyer (1836-1920, British)

• Discovered the element Helium when studying the Sun’s atmosphere. One of the first to detail the astronomy of ancient cultures, in particular, Egypt.

Edward Charles Pickering (1846-1919, American)

• Discovered the spectroscopic binary star (systems in which the stars are so close together that they appear as a single star even through a telescope).

Jacobus Cornelius Kapteyn (1851-1922, Dutch)

• Discovered evidence for galactic rotation by demonstrating that the motions of stars were not random.

Edward Emerson Barnard (1857-1923, American)

• Discovered the star which was then to be named Barnard’s Star in his honor. The star was notable for having a high degree of proper motion relative to other astronomical objects.
• Discovered the fifth moon of Jupiter, Amalthea. The first four had been discovered by Galileo Galilei centuries earlier.
• He was also a pioneering astrophotographer and cataloged a series of dark nebulae, known as Barnard objects.

Annie Jump Cannon (1863-1941, American)

• Cannon developed a system to classify and organize stars according to the temperatures they produced. She classified 400,000 stars into the scheme that is still used today and discovered 300 variable stars.

Max Wolf (1863-1932, German)

• Pioneering astrophotographer who discovered hundreds of asteroids and four supernovae. He helped uncover that dark nebulae were huge clouds of fine opaque dust using photographic techniques.

Henrietta Swan Leavitt (1868-1921, American)

• Discovered that a particular type of variable star known as a Cepheid could be used as a distance marker, making it possible to determine astronomical distances to objects. This discovery first allowed astronomers to measure the distance between the Earth and faraway galaxies.

George Ellery Hale (1868-1938, American)

• The first astronomer to be officially called an astrophysicist. Hale discovered the magnetic fields in sunspots and was a key figure in founding three important observatories: Yerkes, Mt. Wilson, and Palomar.

Willem de Sitter (1872-1934, Dutch)

• Devised a solution for Einstein’s theory of general relativity which deduced that a near-empty universe would expand.

Karl Schwarzschild (1873-1916, German)

• Provided the first exact solution to Einstein’s equations of general relativity, giving an understanding of the geometry of space near a point mass.
• The first to study the theory of black holes.

Ejnar Hertzsprung (1873-1967, Danish)

• One of the inventors of the Hertzsprung-Russell diagram (with Henry Norris Russell) – a system classifying stars by spectral type, stage in their development, and luminosity that is still used today.

Kiyotsugu Hirayama (1874-1943, Japanese)

• Discovered the existence of groups of asteroids with similar orbitals which led to the concept of asteroid families (now called Hirayama families).

Vesto Slipher (1875-1969, American)

• Performed the first measurements of radial velocities for galaxies thereby providing the empirical basis for the expansion of the universe. Supervised the work that led to the discovery of Pluto in 1930.

Walter Sydney Adams (1876-1956, American)

• Demonstrated that spectra could be used to determine whether a star was a giant or a dwarf and identified the first white dwarf star, Sirius B.

Henry Norris Russell (1877-1957, American)

• Along with Ejnar Hertzsprung, Russell invented the Hertzsprung-Russell diagram to classify the spectral types of stars.

Bernhard Schmidt (1879-1935, German)

• Invented the Schmidt telescope which corrected for the optical errors of spherical aberration, coma, and astigmatism, making possible the construction of large, wide-angled reflective cameras for astronomical research.

Albert Einstein (1879-1955, German-Swiss)

• Considered the greatest mind of the 20th century, he developed the theory of relativity – one of the two pillars of modern physics (alongside quantum mechanics).
• His Special Theory of Relativity built on Newtonian Mechanics describes the changes in measurements of physical phenomena when viewed by observers who are in motion relative to the phenomena.
• He later extended the principle of relativity to gravity and subsequently developed his General Theory of Relativity. According to the theory, the gravitational attraction between masses results from the warping of space and time by those masses. This is today an essential element in modern astrophysics and provides the foundation for the current understanding of black holes – regions of space where gravitational attraction is so strong that not even light can escape.

Arthur Eddington (1882-1944, English)

• Eddington was the first to confirm Einstein’s prediction that light will bend near a star.
• He explained the behavior of Cepheid variables – a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness.
• Discovered the relationship between the mass of a star and its luminosity. The Eddington limit, the natural limit to the luminosity of stars, is named in his honor.

Harlow Shapley (1885-1972, American)

• Calculated the size of the Milky Way and the Sun’s position within it.

Edwin Hubble (1889-1953, American )

• Provided evidence that the universe is expanding by measuring distances between galaxies and discovered that they are moving away from us. This is known as Hubble’s law and is a cornerstone of the Big Bang model of the universe.
• In making his observations beyond the Milky Way, he discovered galaxies including Triangulum and the Andromeda Nebula. Hubble also organized galaxies into three classes – spirals, ellipticals, and irregulars. In discovering further galaxies, he vastly increased the known universe for mankind from a galaxy of one hundred billion stars (we now estimate it to be double this), to a much vaster expanse of intergalactic space billions of light-years across.

Walter Baade (1893-1960, German)

• Observed and defined two distinct “populations” for stars (the younger, hotter Population I, and the older, cooler Population II). The same observations led him to discover that there are two types of Cepheid variable stars.
• Recalculated the size of the known universe, doubling the previous calculation made by Hubble in 1929, and discovered the asteroids Hidalgo and Icarus.

Georges-Henri Lemaitre (1894-1966, Belgian)

• Proposed what became known as the Big Bang theory of the origin of the universe.

Rudolph Minkowski (1895-1976, German-American)

• Together with Walter Baade, classified supernovae into Types I and II (sub-divided based on their spectra).
• Co-discovered the near-Earth Apollo asteroid 1620 Geographos, and the planetary nebula M2-9.

Bernard-Ferdinand Lyot (1897-1952, French)

• Invented the coronagraph in order to observe the corona (the aura of plasma that surrounds the Sun) without having to wait for a solar eclipse.

Otto Struve (1897-1963, Russian-born American)

• Struve made detailed spectroscopic studies of close binary stars, discovered interstellar matter (H II regions), and was an early advocate of the possibility of extraterrestrial life.

Fritz Zwicky (1898-1974, Swiss-American)

• Zwicky was the first to theorize the existence of unseen dark matter in the universe and discovered 18 supernovas in 4 years, when previously only 12 had been known of.
• Also anticipated the discovery of quasars and proposed the existence of – and then observed – dwarf galaxies.

Cecilia Payne-Gaposchkin (1900-1979, British-American)

• Established that stars are composed primarily of hydrogen and that accordingly, this was the most abundant element in the Universe, with helium second.
• In leading Harvard’s Department of Astronomy, was the first woman to head a department at that university.

Jan Hendrik Oort (1900-1992, Dutch)

• Oorrt was the first to measure the distance between our solar system and the center of the Milky Way. He also calculated its mass and determined the period for the sun to complete one revolution of the galaxy.
• Proposed the existence of a huge spherical cloud of icy comets (the Oort cloud) left behind from the formation of the solar system.

George Gamow (1904-1968, Russian-American)

• Explained how high levels of helium and hydrogen in the universe could be the result of the reactions that occurred during the Big Bang.
• The first to put forward the idea that solar energy comes from the process of nuclear fusion and discovered a theoretical explanation of alpha decay via quantum tunneling.

Karl Guthe Jansky (1905-1950, American)

• Pioneer of radio astronomy when he discovered radio waves emanating from space.

Gerard Kuiper (1905-1973, Dutch-American)

• Discovered comet-like debris at the edge of the solar system beyond Pluto that was then named the Kuiper belt. He also discovered several moons in the outer solar system and the atmosphere of Saturn’s moon Titan.

Bruno B. Rossi (1905-1993, Italian)

• Pioneer of x-ray astronomy and space plasma physics. Also participated in the discovery of the first known x-ray source outside the solar system (Scorpius X-1).

Bart Bok (1906-1983, Dutch-American)

• Discovered small dark clouds of interstellar gas and dust that collapse to form new stars. These were then to be named Bok globules.

Clyde Tombaugh (1906-1997, American)

• Discovered Pluto photographically in 1930, using the telescope at the Lowell Observatory in Arizona.
• Also discovered hundreds of asteroids as well as galaxy clusters, variable stars, and superclusters.

Fred Lawrence Whipple (1906-2004, American)

• Proposed the “dirty snowball” model of cometary hypothesis relating to the amount of ice in a comet’s mass.
• Also invented the Whipple shield, used to protect spacecraft from collisions with micrometeoroids and orbital debris.

Hannes Alfvén (1908-1995, Swedish)

• Developed the theory of magnetohydrodynamics (MHD) – the study of the magnetic properties of electrically conducting fluids – that has implications for astrophysics.

Viktor Ambartsumian (1908-1996, Soviet-Armenian)

• One of the founders of theoretical astrophysics.

Subrahmanyan Chandrasekhar (1910-1995, Indian-American)

• Made important theoretical contributions concerning the structure and evolution of stars and black holes.
• He found that white dwarf stars have a limit of 1.4 solar masses and any star larger than this cannot be stable as a white dwarf. This is now called the Chandrasekhar limit.

Carl Keenan Seyfert (1911-1960, American)

• Studied a group of galaxies which are now named Seyfert galaxies.

William Fowler (1911-1995, American)

• Conducted experimental studies of nuclear reactions that advanced astrophysics and developed, with others, a complete theory of the formation of chemical elements in the universe.

Famous astronomers of the 21st century

Grote Reber (1911-2002, American)

• Built the first radio telescope and for nearly a decade he was the world’s only radio astronomer.

John Archibald Wheeler (1911-2008, American)

• Theoretical physicist who made contributions to the understanding of quantum gravity and coined many terms such as “wormhole”.

Carl Friedrich von Weizsäcker (1912-2007, German)

• Contributed theoretical work on planetary formation in the early Solar System and proposed (with Hans Bethe) the proton-proton reaction as the thermonuclear energy source for the sun.

James Van Allen (1914-2006, American)

• Discovered the magnetosphere of the Earth. The Van Allen radiation belts are named after him following their discovery by his Geiger–Müller tube instruments on satellites in 1958.

Sir Fred Hoyle (1915-2001, British)

• Coined the term “Big Bang” but rejected the theory in favor of the steady-state model of the universe.
• A prominent author of science fiction, he believed that early life forms were transported by comets and that the interaction of a comet with the Earth is how life appeared on our planet.

Robert H. Dicke (1916-1997, American)

• Proposed that it was possible to detect radiation left over from the Big Bang and invented the microwave radiometer to detect this.

Margaret Burbidge (1919-now, British-American)

• One of the pioneers in the spectroscopic study of quasars, she proved that all the elements except the very lightest, are produced by nuclear processes inside stars. Discovered that the galaxy M82 has a massive black hole at its center.

Thomas Gold (1920-2004, Austrian-British)

• Helped create the Steady State theory of the universe (now mostly abandoned in favor of the Big Bang Theory).
• Coined the term “magnetosphere” for a planet or object controlling particles by way of magnetic fields.
• Contributed to our understanding of cosmology, the nature of pulsars as rotating neutron stars, and the origin of planetary hydrocarbons.

George Howard Herbig (1920-2013, American)

• Discovered Herbig-Haro objects – gas clouds associated with newly born stars.

Chushiro Hayashi (1920-2010, Japanese)

• Delivered the astrophysical calculations that led to the Hayashi tracks of star formation.
• Also calculated the maximum radius for a star of a given mass – now known as the Hayashi limit.

Edwin Ernest Salpeter (1924-2008, Austrian–Australian–American)

• Explained how the triple-alpha process could make carbon from helium in stars.
• Co-developed the Bethe-Salpeter equation, which describes the interactions between a pair of fundamental particles under a quantum field theory.

Antony Hewish (1924-now, British)

• Hewish led the research group that discovered the first pulsar – a highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation.

Allan Rex Sandage (1926-2010, American)

• Identified the first quasar – a supermassive black hole surrounded by an orbiting accretion disk of gas.
• Accurately estimated the age of the universe.

Vera Rubin (1928-2016, American)

• Pioneered work on galaxy rotation rates and ultimately concluded that 90% or more of the universe is made of invisible dark matter.

Bernard F. Burke (1928-now, American)

• Co-discovered that Jupiter is a source of radio waves.

Irwin I. Shapiro (1929-now, American)

• Pioneered radar techniques for various astrophysical research activities.

Riccardo Giacconi (1931-now, Italian-American)

• Pioneer of x-ray astronomy that led to the discovery of the first cosmic x-ray sources from outside the solar system.

Sir Roger Penrose (1931-now, British)

• Put forward possible evidence of an earlier universe that existed before the Big Bang and advanced thought on black holes.
• His Penrose Interpretation predicts the relationship between quantum mechanics and general relativity.

Arno Allan Penzias (1933-now, German-American)

• Co-discovered (with Robert Woodrow Wilson) the cosmic microwave background radiation left over from the Big Bang. This led to wide acceptance of the Big Bang theory and the main opposing theory, the Steady State theory, was virtually abandoned.

John N. Bahcall (1934-2005, American)

• Made important theoretical contributions to understanding solar neutrinos and quasars and was part of the development of the Hubble Space Telescope.

Carl Sagan (1934-1996, American)

• Popularized astronomy with the public through the 1980 television series The Cosmos (remade in recent years with Neil deGrasse Tyson), as well as popular science books and science fiction novels (Contact – later made into the 1997 movie of the same name).
• Promoted the Search for Extraterrestrial Intelligence (SETI) program and assembled the first physical messages sent into space.
• Warned that nuclear war could lead to a ”nuclear winter” (a term he coined).

Robert Woodrow Wilson (1936-now, American)

• As above, co-discoverer (with Arno Allan Penzias) of the cosmic microwave background radiation, which proved the best-available evidence for the Big Bang.
• https://en.wikipedia.org/wiki/Robert_Woodrow_Wilson

James W. Christy (1938-now, American)

• Discovered Pluto’s moon, which he named Charon.

William Kenneth Hartmann (1939-now, American)

• Co-developed the most widely accepted theory of the formation of the Moon and the Earth’s tilt – that it resulted from the collision of a planet called Theia around 4.5bn years ago.

Kip Thorne (1940-now, American)

• One of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity.
• Contributed to the theoretical understanding of black holes and gravitational radiation. Co-founded the Laser Interferometer Gravitational Wave Observatory Project (LIGO) – a multi-institution gravitational wave experiment.
• Co-conceived the concept of the Christopher Nolan movie, Interstellar, and wrote the book The Science of Interstellar to explain the ideas that the movie was based on.

Joseph Hooton Taylor Jr. (1941-now, American)

• Co-discovered (Russell Alan Hulse) the first pulsar in a binary system which led to the first confirmation of the existence of gravitational radiation.

Stephen Hawking (1942-now, British)

• The first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics and devised the theoretical prediction that black holes emit radiation and eventually evaporate – called the “Hawking radiation theory”.
• His 1988 book, A Brief History of Time, sold more than 10 million copies and has been translated in 35 languages. A brilliant and prominent mind of the 20th and 21st centuries. His success has been despite being completely immobile as a result of Lou Gehrig’s disease. His life was the basis of the 2014 movie, The Theory of Everything.

Jocelyn Bell Burnell (1943-now, British)

• Co-discovered the first pulsar as a student and went on to discover three more. This is a neutron star that produces electromagnetic radiation.

Charles Thomas Bolton (1943-now, American)

• Discovered the first identified black hole, Cygnus X-1.

James Ludlow Elliott (1943-2011, American)

• Discovered the rings of Uranus and observed global warming on Triton, the largest moon of Neptune.

Alan Guth (1947-now, American)

• Developed a new theory called the inflationary universe that complements the Big Bang Model and predicts that the universe is flat and infinite.

Russell Alan Hulse (1950-now, American)

• As above, co-discovered the first binary pulsar with Joseph Hooton Taylor Jr.

Neil deGrasse Tyson (1958-now, American)

• A popular advocate of modern science and astronomy by hosting the television series, Cosmos: A SpaceTime Odyssey.
• He has published several popular books about astronomy, astrophysics, and black holes.

Rafael Rebolo López (1961-now, Spanish)

• Led the Spanish team (along with Maria Rosa Zapatero Osorio and Eduardo Martín) in 1994 that discovered the first confirmed Brown Dwarf – substellar objects that occupy the mass range between the heaviest gas giant planets and the lightest stars.
• Discovered several giant exoplanets in 2000.

Michael E. Brown (1965-now, American)

• Discovered many trans-Neptunian objects (TNOs) including Eris, a dwarf planet that was the first TNO discovered that is larger than Pluto. This eventually led to the demotion of Pluto from a planet to a dwarf planet.
• Listed as one of Time Magazine’s 100 Most Influential People in 2006.

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