The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for l...

Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of icy trans-Neptunian objects. It was the first such object to be discovered. It is the largest and second-most massive known dwarf planet in the S...

Venus is the second planet from the Sun and the sixth largest. On June 8 2004, Venus will pass directly between the Earth and the Sun, appearing as a large black dot travelling across the Sun's disk. This event is known as a "transit of Ve...

The zodiac is an area of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon a...

Paolo dal Pozzo Toscanelli was an Italian mathematician, astronomer, and cosmographer. Toscanelli is noted for his observations of comets and the painstaking calculation of their orbits. Among these was the comet of 1456; only named Halley'...

Gerardus Mercator, Flemish cartographer. He received a master's degree in 1532 from the University of Louvain (Belgium), where he settled. By 24 he was a skilled engraver, calligrapher, and scientific-instrument maker. He and his colleagues...

Giordano Bruno was an Italian Dominican friar, philosopher, mathematician, poet, and cosmological theorist. He is known for his cosmological theories, which conceptually extended the then-novel Copernican model. He proposed that the stars w...

Andreas Cellarius was a Dutch-German cartographer, best known for his Harmonia Macrocosmica of 1660, a major star atlas, published by Johannes Janssonius in Amsterdam. He was born in Neuhausen (now a part of Worms), and was educated in H...

Georges-Louis Leclerc, Comte de Buffon was a French naturalist, mathematician, cosmologist, and encyclopedic author. His works influenced the next two generations of naturalists, including Jean-Baptiste Lamarck and Georges Cuvier. Buffon pu...

Pierre-Simon, marquis de Laplace, was an influential French scholar whose work was important to the development of mathematics, statistics, physics, and astronomy. He summarized and extended the work of his predecessors in his five-volume M...

Caroline Lucretia Herschel was a German astronomer, whose most significant contributions to astronomy were the discoveries of several comets, including the periodic comet 35P/Herschel–Rigollet, which bears her name. She was the younger sist...

Alexander von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher, and linguist, Wilhelm von Humboldt (1767-1835). Humboldt's quantitative work on botanical geography was foundational...

Sir George Biddell Airy was an English mathematician and astronomer, Astronomer Royal from 1835 to 1881. His many achievements include work on planetary orbits, measuring the mean density of the Earth, a method of solution of two-dimensiona...

Kristian Olaf Bernhard Birkeland was a Norwegian scientist. He is best remembered as the person who first elucidated the nature of the Aurora borealis. In order to fund his research on the aurorae, he invented the electromagnetic cannon and...

Erwin Schrödinger, sometimes written as Erwin Schrodinger or Erwin Schroedinger, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum theory, which formed the basis of wave mecha...