Few areas of astronomy or astrophysics have been as explosive over recent years as the cottage industry of extrasolar planet discoveries. At the time of writing in early 2015, astronomers know of more than 1,800 planets orbiting more than 1,100 stars other than the Sun, all relatively nearby in the Milky Way Galaxy. The most productive discoverer of exoplanets, NASA's Kepler spacecraft, has produced a total of some 1,000 confirmed exoplanets and 2,900 exoplanet candidates that await confirmation with additional data. The pace of discoveries and confirmations has been so dizzying ‒ especially during the busiest periods of analyzing data from various instruments dedicated to the task ‒ that the count of exoplanets has changed from week to week.
Speculations and crude research on the existence of planets beyond the solar system go back a long way. In the sixteenth century, Italian philosopher Giordano Bruno (1548–1600) speculated on the “infinity of worlds” that should exist out in the vastness of the stars. Similarly, in the conclusion of his fantastic tome Principia Mathematica, Isaac Newton suggested that stars are the centers of systems like the Sun and planets.
The first claims of a detection of exoplanets rolled along in the nineteenth century. Claims of detecting a “dark body” affecting the orbit of the star 70 Ophiuchi, a 4th-magnitude star lying 16.6 light-years distant, stretch back to 1855, when observers at the East India Company's Madras Observatory reported wobbles in the star's position in the sky. Similarly, American astronomer Thomas Jefferson Jackson See (1866–1962), an eccentric underachiever, claimed observations that proved such a body in 70 Oph throughout the 1890s. But these were subsequently discredited. Sixty years later, Dutch astronomer Peter van de Kamp (1901–1995), working at Swarthmore College's Sproul Observatory, claimed detection of a planet orbiting another close star, Barnard's Star. This star, also in Ophiuchus, has the highest degree of motion relative to the background stars in the sky, at a distance of only 6.0 light-years. But the van de Kamp observations also proved to be erroneous.
The first confirmed detection of a planet outside the solar system was announced in 1992, when Polish‒American astronomer Aleksander Wolszczan (1946–) and Canadian–American astronomer Dale Frail described their detection of two planets orbiting the pulsar PSR B1257+12.