Commentariolus
Circulates a short manuscript outlining a heliocentric planetary system.
Astronomy topic guide · World History Database
History of Exoplanet Discovery
The modern search for planets beyond the Solar System moved from speculation to confirmed discovery in the early 1990s. Planets around a pulsar were confirmed first, followed in 1995 by 51 Pegasi b, the first confirmed planet orbiting a Sun-like star. Radial-velocity surveys revealed many hot Jupiters, while transit missions such as Kepler demonstrated that planets are common. Astronomers now study exoplanet sizes, masses, atmospheres and system architectures, with space telescopes extending the field from discovery into detailed characterisation.
What this chronology covers
Exoplanet astronomy progressed because different detection methods reveal different kinds of worlds. Pulsar timing demonstrated that planets could be detected indirectly with extraordinary precision. Radial-velocity surveys found massive planets close to their stars, while transit surveys measured planetary radii across large samples. Direct imaging, microlensing and atmospheric spectroscopy have since expanded the field. The result is a historical shift from asking whether other planetary systems exist to studying how common and diverse they are.
47matching astronomy records
2,423records in the complete astronomy database
Selected database timeline
The records below are drawn from the existing World History Database astronomy collection and arranged chronologically. For very broad subjects, the page shows a substantial selection rather than duplicating the entire parent database.
Sunspots
Previous sunspot observations had been misinterpreted as planetary transits, until Galileo gave the correct explanation in 1612
Transit of Mercury Prediction
Kepler's Rudolphine Tables predict that Mercury will cross the face of the Sun in November 1631.
Transit of Venus Prediction
Kepler's Rudolphine Tables predict a transit of Venus for 1631, although the event is not visible from Europe.
First Telescopic Planetary Transit
Records the first telescopic observation of a planetary transit.
Transit of Mercury Observed
Observes Mercury crossing the Sun as predicted by Kepler.
Transit of Venus Prediction
Horrocks corrects earlier calculations and predicts that Venus will transit the Sun in December 1639.
Transit of Venus Observed
Horrocks observes the first recorded transit of Venus from Much Hoole after projecting the Sun's image safely.
Transit of Venus Observed
Crabtree independently observes the 1639 transit of Venus after Horrocks alerts him to the predicted event.
Astronomical Unit
Gregory proposes using observations of a planetary transit from widely separated locations to determine the scale of the Solar System.
Mercury Transit Timing
Halley's Mercury transit observations strengthen interest in using accurately timed planetary transits to refine measurements of the Solar System.
Transit of Mercury
Halley observes a transit of Mercury from Saint Helena and carefully records the event for later astronomical analysis.
Transit of Venus Method
Halley publishes a method for using future transits of Venus to calculate the Earth-Sun distance more accurately.
Transit of Mercury
Messier documents the transit of Mercury
Indian Ocean Transit Observations
Contributes to international efforts to determine the astronomical unit.
Transit of Venus Expedition
Attempts to observe the Venus transit during an extended scientific voyage.
Atmosphere of Venus
Lomonosov observes a luminous arc during the transit of Venus and concludes that the planet possesses an atmosphere.
Transit of Venus Expedition
Mason observes the transit of Venus from the Cape of Good Hope after wartime conditions disrupt the expedition's original destination.
Transit of Venus Expedition
Dixon joins Charles Mason in observing the transit of Venus from the Cape of Good Hope for international distance measurements.
Transit of Venus
Le Gentil reaches Pondicherry for the 1769 transit but clouds prevent him from observing the event after years of travel.
Transit of Venus Expedition
Cook's expedition observes the transit of Venus from Tahiti as part of an international effort to determine the astronomical unit.
Transit of Venus Observed
Green makes timed observations of the Venus transit from Tahiti during Cook's scientific expedition.
Transit of Venus Observed
Rittenhouse leads observations of the transit of Venus in Pennsylvania for measurements of the Earth-Sun distance.
Airy Transit Circle
Installs the transit instrument later defining the Greenwich prime meridian.
Transit of Venus Photography
Janssen uses his photographic revolver during the transit of Venus to record a rapid sequence of solar images.
Belgian Venus Transit Observations
The programme contributes measurements intended to refine the astronomical unit.
Belgian Venus Transit Programme
Supports measurement of the astronomical unit through coordinated observations.
Transit of Venus Expedition
Organizes Belgian observations of the transit of Venus.
Transit of Venus Expeditions
Organizes Belgian expeditions to observe the transit of Venus.
Discovery of Supernova
Zwicky and Baade coin the term "supernova" and hypothesized that they were the transition of normal stars into neutron stars, as well as the origin of cosmic rays. In support of this hypothesis, Zwicky started hunting for supernovae, and found a total of 120 by himself (and one more, SN 1963J, in concert with Paul Wild) over a stretch of 52 years
Beta Transitions Paper
Hoyle submitted research on beta transitions in a Coulomb field for scientific review.
Exoplanets
Alex Wolszczan and Dale Frail at Pennsylvania State University report evidence of 3 extra-solar planets (exoplanets) orbiting around the spinning remains of Pulsar B1257+12
Exoplanets
Alex Wolszczan and Dale Frail at Pennsylvania State University report evidence of 3 extra-solar planets (exoplanets) orbiting around the spinning remains of Pulsar B1257+12
First Confirmed Exoplanet System
Publishes evidence for planets orbiting pulsar PSR B1257+12.
Pulsar Planet Discovery
Reports the first confirmed planetary system beyond the Solar System.
First Exoplanet Atmosphere Measurement
Hubble detects sodium in the atmosphere of HD 209458b, providing the first direct atmospheric measurement of an exoplanet.
Evaporating Exoplanet Atmosphere
Vidal-Madjar leads Hubble observations showing hydrogen escaping from HD 209458b in an extended comet-like atmosphere.
Cosmic Transition from Deceleration
Riess uses very distant Type Ia supernovae to identify evidence that the universe once decelerated before dark energy became dominant and expansion began accelerating.
Transit of Venus
Pasachoff participates in scientific observations of the first transit of Venus visible since 1882.
Methane in Exoplanet Atmosphere
Swain leads Hubble observations detecting methane in HD 189733b, the first organic molecule identified in an exoplanet atmosphere.
Fomalhaut Exoplanet Imaging
Kalas leads Hubble observations that reveal a visible-light point source moving around Fomalhaut within its debris system.
Transit of Venus
Pasachoff observes the final transit of Venus of the twenty-first century, an event not repeated until 2117.
Kepler-1625b Exomoon Evidence
Teachey uses Hubble data with Kepler observations to report evidence for a possible large moon orbiting exoplanet Kepler-1625b.
Voyager 2 Heliopause Plasma Signature
Uses Voyager 2 plasma measurements to identify the sharp transition from the heliosphere into interstellar space.
Water Vapor on K2-18b
Tsiaras leads analysis of Hubble spectra detecting water vapor in the atmosphere of habitable-zone exoplanet K2-18b.
Growing Exoplanet PDS 70b
Zhou leads Hubble ultraviolet observations of the young planet PDS 70b actively accreting material from its surrounding disk.
LTT 1445Ac Size
Pass leads Hubble observations refining the radius of nearby transiting exoplanet LTT 1445Ac and confirming its Earth-like size.
Related astronomers
AryabhataProfile and database timelineBhaskara IIProfile and database timelineNicolaus CopernicusProfile and database timelineTycho BraheProfile and database timelineGalileo GalileiProfile and database timelineJohannes KeplerProfile and database timelineEdmond HalleyProfile and database timelineWilliam HerschelProfile and database timeline
Sources and editorial provenance
Compiled and edited by World History Database
Historical chronology compiled from the World History Database and checked against major scientific and historical reference sources.
Last reviewed: September 2026.
- Royal Museums Greenwich — History of astronomy
- Royal Museums Greenwich — History of the telescope
- NASA Science — Hubble timeline
- NASA Science — Exoplanet discovery history
- LIGO — GW150914 first gravitational-wave detection
- Event Horizon Telescope — first black-hole image
- NASA Webb — mission science and discoveries