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

**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** 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.

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 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** 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.

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

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.

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

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.

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

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

**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.

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?'' .

**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.

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

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

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.

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

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

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

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

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

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.

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

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.

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.

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

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.

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

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.

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 .