The original discovery image of a disk of dust and gas around the star Beta Pictoris, taken with the du Pont 2.5-meter telescope at the Las Campanas Observatory in Chile in April, 1984. Image credit: Bradford A. Smith, Richard J. Terrile, NASA.

Influential mission will later aid in the identification and study of exoplanets by watching for the dimming caused when a planet moves in front of its star.

Aleksander Wolszczan and Dale Frail announce the discovery of two rocky planets orbiting PSR B1 257+12, a pulsar in the constellation Virgo. Because they are constantly bombarded by radiation from the dead neutron star that they orbit, these rocky planets cannot support organic life.   A year later, the planet PSR B1620-26 b is found orbiting a binary system composed of a pulsar and a white dwarf. Located 1,170 light years from Earth, the planet, which is about two and a half times the size of Jupiter, takes over 100 Earth years to complete a single orbit. It is also the first planet found in a star cluster (globular cluster M4).

Didier Queloz and Michel Mayor announce their discovery of the first planet orbiting a main ­sequence star, 51 Pegasi. The planet, which is half the size of Jupiter, practically grazes the surface of its star, a revelation that baffles astronomers. Later discoveries indicate that this type of close-orbiting planet, nicknamed a "roaster," is a common phenomenon.

Research teams led by David Charbonneau and Greg Henry independently observe a planet passing across the front of the star HD 209458 in the constellation Pegasus. This observation allows astronomers to analyze the atmosphere of the planet, which they believe contains water, oxygen, nitrogen, and carbon. Because of the planet's close orbit of its star, its atmosphere is being stripped off, forming a tail behind the planet similar to a comet’s. Image: Artist's concept of the HD 209458 system. (credit NASA)

Researchers from San Francisco State University and the Harvard-Smithsonian Center for Astrophysics, working independently, announce the discovery of two additional planets orbiting the star Upsilon Andromedae in the constellation Pegasus. The three-star system is the first multi-planetary system discovered around another star. Image: A simulated view of the Upsilon Andromedae system. (Credit: Sylvain Korzennik)

Astronomers from Geneva University announce the discovery of HD 28185 b, a planet that orbits about the same distance from its star as Earth does from the sun. The planet, which is nearly six times as massive as Jupiter, is the first to be found in the so-called "habitable zone" around a star, where life could possibly exist. Image: La Silla observatory in Chile, site of the discovery. (Credit: ESO)

Teams led by David Charbonneau and Timothy Brown use the spectrometer on the Hubble Space Telescope to analyze the atmospheric composition of a planet orbiting the star HD 209458.

Suitcase-sized Canadian space telescope is designed to detect brightness changes in stars, and can observe exoplanets transiting their host stars.

Infrared space telescope later begins observations of exoplanets, gathering both size and atmospheric data.

Astronomers using the Spitzer Space Telescope announce direct observation of infrared light from an exoplanet for the first time, from planets HD 209458 b and TrES-1. This marks the first time that astronomers were able to see light emanating from a planet itself, and the beginning of a new type of direct observation of planets. The discovery allows the atmospheres, sizes and orbits of planets to be analyzed. Image: Artist's concept shows what a hot star and its nearby planetary companion might look if viewed close up in visible (left) and infrared light.

French satellite detects planets as they transit across the surface of their stars. Discovers its first planet in May 2007.

Astronomers David Charbonneau and Heather Knutson report using the Spitzer Space Telescope to create the first map of an exoplanet's surface. The rough map shows the temperature of cloud cover on the surface of HD 189733 b. (Credit NASA’s Goddard Space Flight Center).

Gas giants HD 209458 b and HD 189733 b are the first two planets to have their spectra observed using the Spitzer Space Telescope, astronomers announce. The readings provide information about each planet's atmosphere. This method of detection is thought to be a way to observe signs of extraterrestrial life. [credit NASA, ESA, G. Bacon (STScI) and N. Madhusudhan (UC)]

A Delta II rocket carrying NASA’s Kepler space telescope blasts off from Cape Canaveral Air Force Station in Florida. Kepler will stare for four years at a patch of sky containing 150,000 stars, watching for tiny dips in starlight as planets crossed in front of some of them. The pioneering spacecraft will find more than 1,000 confirmed exoplanets—a gold rush of discovery—before a malfunction ends its primary mission in 2013.

NASA’s Kepler mission announces the discovery of its first rocky exoplanet, and the smallest planet found outside the solar system up to that point. Kepler-10b, 1.4 times the size of Earth, has the density of an iron dumbbell, weighs in at 4.6 times the mass of Earth. It is also extremely hot, with an orbit more than 20 times closer to its star than Mercury to our sun.

Relying on data from the Kepler and Spitzer space telescopes, astronomers announce the creation of the first cloud map of a planet outside our solar system—a scorching world 50 percent larger than Jupiter called Kepler-7b. Spitzer helped astronomers determine that light from Kepler-7b’s star was bouncing off cloud tops in the planet’s western hemisphere.

The first Earth-sized planet orbiting within its star’s habitable zone—where liquid water could exist on a planetary surface—is revealed by the Kepler space telescope team. Kepler-186f, just 10 percent larger than Earth and thought to be rocky, orbits a star about half the size of our sun some 500 light years away.

After mechanical troubles end its first four years of observation, the Kepler mission begins anew as K2, using the pressure of sunlight to help stabilize the space telescope. This requires switching to a new field of view every three months.

Earth’s “bigger, older cousin,” Kepler-452b, makes its public debut. About 1.6 times the size of Earth, this planet’s main claim to fame is its 385-day orbit around a G2-type star—very much like our own orbit, and very much like our own sun. Considered a “super Earth,” Kepler-452b, if rocky, could have liquid water on its surface, although its true composition remains unknown.

The Kepler mission hauls in a historical cache of more than 1,200 exoplanets. Almost 40 percent could be rocky planets with a composition similar to Earth’s. Image credit: NASA/W. Stenzel.

A planet that is probably rocky and a bit more massive than Earth is discovered around our nearest neighboring star, Proxima Centauri. The new planet, Proxima b, orbits its star at a distance that could allow liquid water to form on its surface. Image credit: ESO/M. Kornmesser (artist's rendering).

NASA announces the discovery of seven sibling planets orbiting TRAPPIST-1, a star some 40 light-years away. All are in Earth’s size range and some are in the star’s habitable zone. Future studies will help determine whether they have atmospheres, oceans or even potential signs of life. Image credit: NASA/JPL-Caltech (artist's rendering).

An eighth planet is found in the Kepler-90 system – equal to our own solar system in having the largest number of known planets. All crowd closer to their star than Earth to our Sun. The discovery is made with the help of artificial intelligence.

In a two-year survey of the solar neighborhood, TESS will monitor the brightness of stars for periodic drops caused by planet transits. The TESS mission is expected to find planets ranging from small, rocky worlds to giant planets, showcasing the diversity of planets in the galaxy.

The first-ever detection of the second-most common element, long anticipated, was made with NASA’s Hubble Space Telescope. Helium was found in the atmosphere of WASP-107b, a gas giant more than 200 light-years from Earth.

The latest planet-hunting space telescope delivers its first science image, a portrait of the Large Magellanic Cloud – one of our Milky Way’s small, satellite galaxies.

NASA bids “good night” to the Kepler space telescope, instructing it to sever communications with Earth after running out of fuel and ending science operations. The spacecraft, which discovered thousands of exoplanets over its nine-year lifespan, will continue to drift in a safe orbit around the Sun.

The freshly launched TESS space telescope finds its first three confirmed exoplanets: LHS 3844b, Pi Mensae c, and HD21749b. Image credit: NASA/MIT/TESS.

NASA's Exoplanet Archive announces 31 newly confirmed exoplanets discovered by ground and space-based telescopes. Five were detected by the recently launched TESS space telescope. They push the official planet count past the 4,000 mark for the first time.

The James Webb Space Telescope launched on Christmas Day, 2021. Seen here in our last look, still folded for launch, and moving away from Earth. Webb is finding the first galaxies that formed in the early universe and peering through dusty clouds to see stars forming planetary systems. It's also getting our best looks ever at exoplanet atmospheres.

The count of confirmed exoplanets ticks past the 5,000 mark, representing a 30-year journey of discovery led by NASA space telescopes. Not so long ago, we lived in a universe with only a small number of known planets, all of them orbiting our Sun. But a new raft of discoveries marks a scientific high point: More than 5,000 planets are now confirmed to exist beyond our solar system.