# Famous Astronomers

#### Nicolaus Copernicus 1473 - 1543

Copernicus was a Polish astronomer and mathematician who was a proponent of the view of an Earth in daily motion about its axis and in yearly motion around a stationary sun. This theory profoundly altered later workers' view of the universe, but was rejected by the Catholic church.

#### Tycho Brahe 1546 - 1601

Tycho Brahe was a Danish astronomer who is best known for the astronomical observations which led Kepler to his theories of the Solar system.

#### Galileo Galilei 1564 - 1642

Galileo Galilei was an Italian scientist who formulated the basic law of falling bodies, which he verified by careful measurements. He constructed a telescope with which he studied lunar craters, and discovered four moons revolving around Jupiter and espoused the Copernican cause.

#### Johannes Kepler 1571 - 1630

Johannes Kepler was a German mathematician and astronomer who discovered that the Earth and planets travel about the sun in elliptical orbits. He gave three fundamental laws of planetary motion. He also did important work in optics and geometry.

#### John Baptiste Riccioli 1598 - 1671

Riccioli was an Italian astronomer who made telescopic lunar studies and published detailed lunar maps in which he introduced much nomenclature for lunar objects; discovered the first double star (Mizar)

#### Giovanni Domenico Cassini 1625 - 1712

Giovanni Cassini was an Italian mathematician and astronomer who studied the curve which is the locus of a point the product of whose distances from two fixed foci is constant.

#### Christiaan Huygens 1629 - 1695

Christiaan Huygens was a Dutch mathematician who patented the first pendulum clock, which greatly increased the accuracy of time measurement. He laid the foundations of mechanics and also worked on astronomy and probability.

#### Sir Isaac Newton 1643 - 1727

Isaac Newton was the greatest English mathematician of his generation. He laid the foundation for differential and integral calculus. His work on optics and gravitation make him one of the greatest scientists the world has known.

#### Edmond Halley 1656 - 1742

Edmond Halley was an English astronomer who calculated the orbit of the comet now called Halley's comet. He was a supporter of Newton.

#### Charles Messier 1730 - 1817

The celebrated French astronomer Charles Messier became famous in his lifetime for the discovery of 20 comets, 13 of which are still credited to him.

#### Joseph-Louis Lagrange 1736 - 1813

Lagrange excelled in all fields of analysis and number theory and analytical and celestial mechanics.

#### William Herschel 1938 - 1832

Herschel was a British astronomer best known for his discovery of Uranus and its two brightest moons, Titania and Oberon; Saturn's moons, Mimas and Enceladus; the ice caps of Mars, several asteroids and binary stars. He also cataloged 2,500 deep sky objects.

#### Giuseppe Piazzi 1746 - 1826

Piazzi was an Italian astronomer who discovered the largest asteroid, Ceres; accurately measured positions of many stars, resulting in a star catalog.

#### Johann Bode 1747 - 1826

Bode was a German astronomer who popularized a relationship giving planetary distances from the Sun, which became known as ``Bode's law''; predicted an undiscovered planet between Mars and Jupiter, where the asteroids were later found.

#### Pierre-Simon Laplace 1749 - 1827

Laplace proved the stability of the solar system. In analysis Laplace introduced the potential function and Laplace coefficients. He also put the theory of mathematical probability on a sound footing.

#### Heinrich Wilhelm Olbers 1758 - 1840

Olbers was a German astronomer and inventor who invented the first successful method for calculating cometary orbits; discovered several comets, including the comet of 1815, now called Olber's comet; discovered the asteroids Pallas and Vesta; posed the famous Olber's paradox: ``Why is the night sky dark?'' .

#### Friedrich Wilhelm Bessel 1784 - 1846

Bessel determined the positions and proper motions of stars and discoveredthe parallax of 61 Cygni. He also used a method of mathematical analysis involving what is now known as the Bessel function.

#### Joseph Von Fraunhofer 1787 - 1826

He was a German astronomer who made detailed wavelength measurements of hundreds of lines in the solar spectrum; designed an achromatic objective lens.

#### Johann Franz Encke 1791-1865

Discovered the first short-period comet, now called Encke's comet.

#### Fredrich Von Struve 1793-1864

Struve was a German-born Russian who founded the study of double stars; published catalog of over 3000 binary stars; first to measure distance to the star Vega.

#### Willhelm Beer 1797-1850

Beer was a German astronomer who prepared and published maps of the Moon and Mars.

#### Thomas Henderson 1798-1844

Henderson was a Scotttish astronomer and was the first person to measure the distance to a star (Alpha Centuri).

#### William Lassell 1799-1880

British astronomer who discovered Triton, the largest satellite of Neptune.

#### George Biddell Airy 1801 - 1892

Airy was Lucasian professor at Cambridge and Astronomer Royal. He made many major contributions to mathematics and astronomy.

#### Urbain Jean Joseph Le Verrier 1811 - 1877

Urbain Le Verrier is best known for the calculations which led to the discovery of Neptune.

#### Johann Gottfried Gelle 1812-1910

The first person to observe Neptune, based on calculations by French mathematician, Urbain Le Verrier; however, Neptune's discovery is usually credited to Le Verrier and English astronomer, John Crouch Adams, who first predicted its position.

#### Anders Angstrom 1814-1874

A Swedish astronomer who discovered hydrogen in the solar spectrum; source of the Angstrom unit.

#### Daniel Kirkwood 1814-1895

Kirkwood was an American astronomer who discovered the ``Kirkwood gaps'' in the orbits of the asteroids between Mars and Jupiter; explained the gaps in Saturn's rings.

#### William Huggens 1824-1910

A British astronomer and the first to show that some nebulae, including the great nebula in Orion, have pure emission spectra and thus must be gaseous.

#### Sir Joseph Lockyer 1836-1920

A British astronomer who discovered in the solar spectrum a previously unknown element that he named helium.

#### Henry Draper 1837-1882

An american astronomer who made the first photograph of a stellar spectrum (that of Vega); later photographed spectra of over a hundred stars and published them in a catalog; studied spectrum of Orion Nebula, which he showed was a dust cloud.

#### Edward Charles Pickering 1846-1919

An American astronomer who discovered the first spectroscopic binary star, Mizar.

#### Jacobus Cornelius Kapteyn 1851 - 1922

The Dutch astronomer discovered that the proper motions of stars were not random, but stars could be divided into two streams moving in opposite directions, representing the rotation of our galaxy.

#### Edward Barnard 1857-1923

An American astronomer who discovered eight comets and Almathea, the fifth moon of Jupiter; also discovered star with largest proper motion, now called Barnard's star .