Exoplanets

Extracted Attributes

• Definition

  Planets located outside our Solar System

• Detection Bias

  85% of detected exoplanets are within the tidal locking zone

• Research Focus

  Search for extraterrestrial life, planetary habitability, liquid water

• Common Exoplanet Types

  Super-Earths, Mini-Neptunes, Gas giants, Neptunian, Terrestrial

• Range of Orbital Periods

  Less than an hour to thousands of years

• Primary Detection Methods

  Transit photometry, Doppler spectroscopy

• Current Confirmed Exoplanets

  6,007 (as of 2025-09-17)

• Key Observational Instrument

  James Webb Space Telescope (JWST)

• Most Massive Exoplanet Known

  HR 2562 b (approx. 30 times the mass of Jupiter)

• Least Massive Exoplanet Known

  Draugr (approx. 2 times the mass of the Moon)

• Closest Known Exoplanets Distance

  4.2 light-years

• Closest Known Exoplanets Host Star

  Proxima Centauri

• Existence of Extragalactic Planets

  Evidence suggests

• Current Confirmed Planetary Systems

  4,483 (as of 2025-09-17)

• Estimated Rogue Planets (Milky Way)

  Billions or more

• Estimated Potentially Habitable Earth-sized Planets (Milky Way)

  11 billion (rising to 40 billion including red dwarfs)

• Estimated Earth-sized planets in habitable zone (Sun-like stars)

  1 in 5

Timeline

• First possible evidence of an exoplanet was noted. (Source: wikipedia)

  1917

• A different planet was first detected. (Source: wikipedia)

  1988

• First confirmed detection of an exoplanet around a pulsar. (Source: summary)

  1992

• First detection of an exoplanet around a main-sequence star. (Source: summary)

  1995

• Upsilon Andromedae became the first main-sequence star known to have multiple planets. (Source: web_search_results)

  1999

• The planet first detected in 1988 was confirmed. (Source: wikipedia)

  2003

• It was recognized that the first possible evidence of an exoplanet had been noted in 1917. (Source: wikipedia)

  2016

• 6,007 confirmed exoplanets in 4,483 planetary systems. (Source: summary)

  2025-09-17

Exoplanet

An exoplanet or extrasolar planet is a planet outside of the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detected in 1988, was confirmed in 2003. In 2016, it was recognized that the first possible evidence of an exoplanet had been noted in 1917. As of 17 September 2025, there are 6,007 confirmed exoplanets in 4,483 planetary systems, with 1,009 systems having more than one planet. There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. About 1 in 5 Sun-like stars are estimated to have an "Earth-sized" planet in the habitable zone. Assuming there are 200 billion stars in the Milky Way, it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if planets orbiting the numerous red dwarfs are included. The least massive exoplanet known is Draugr, which is about twice the mass of the Moon. The most massive exoplanet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter. However, according to some definitions of a planet (based on the nuclear fusion of deuterium), it is too massive to be a planet and might be a brown dwarf. Known orbital times for exoplanets vary from less than an hour (for those closest to their star) to thousands of years. Some exoplanets are so far away from the star that it is difficult to tell whether they are gravitationally bound to it. The nearest exoplanets are located 4.2 light-years (1.3 parsecs) from Earth and orbit Proxima Centauri, the closest star to the Sun. At the other extreme, there is evidence for extragalactic planets – exoplanets located in other galaxies. The discovery of exoplanets has intensified interest in the search for extraterrestrial life. There is special interest in planets that orbit in a star's habitable zone (sometimes called "goldilocks zone"), where it is possible for liquid water, a prerequisite for life as we know it, to exist on the surface. However, the study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life. In collaboration with ground-based and other space-based observatories, the James Webb Space Telescope (JWST) is expected to give more insight into exoplanet traits, such as their composition, environmental conditions, and habitability. Rogue planets are those that are not in planetary systems. Such objects are generally considered in a separate category from planets, especially if they are gas giants, often counted as sub-brown dwarfs. The rogue planets in the Milky Way possibly number in the billions or more.

Web Search Results

• Exoplanets, worlds beyond the Solar System - The Planetary Society

  An exoplanet, short for “extrasolar planet,” is any planet that isn’t in the Solar System. Some are gas giants like Jupiter and Saturn, some are rocky like Mercury or Mars, and others are icy like Neptune or Uranus. A select fraction — we’re not quite sure how many — could be like Earth, rocky and with liquid water on their surfaces. [...] > ## Highlights > > Scientists have discovered more than 5,000 planets outside of the Solar System, or “exoplanets”. > Most stars in our galaxy have at least one exoplanet, and many are unlike any of the worlds in the Solar System. > Some exoplanets could be habitable and are prime targets in the search for life beyond Earth. ## What are exoplanets? [...] There are also many exoplanets that don’t look like anything we have in the Solar System. One of the most common kinds of planets are “super-Earths” and “mini-Neptunes”, so called because they are larger than Earth but smaller than Neptune. No world like this exists around the Sun. There are also planets, called “free-floating” or “rogue planets,” that originally formed around a star but then got thrown out to drift through space alone. There are planets that orbit their host stars in hours,

• Exoplanets - NASA Science

  An exoplanet is any planet beyond our solar system. Most of them orbit other stars, but some free-floating exoplanets, called rogue planets, are untethered to any star. We’ve confirmed more than 6,000 exoplanets, out of the billions that we believe exist. Image 39: The TRAPPIST-1 star, an M dwarf, is seen to the left of its seven planets. It is glowing red, while the planets are about the same sizes, but their colors and surface features differ. Unable to render the provided source [...] The official number of exoplanets — planets outside our solar system — confirmed by NASA has reached 6,000. The first exoplanet around a Sun-like star was discovered 30 years ago. Since then, the number has rapidly increased as technologies improve. Thousands more candidate planets await confirmation, and each confirmed planet enables scientists to learn more about the conditions under which planets can form, how common planets like Earth might be, and where to look for them. [...] So far scientists have categorized exoplanets into the following types: Gas giant, Neptunian, super-Earth, and terrestrial, with subcategories — such as mini-Neptunes — within those groups. How are they alike or different? What makes them special? Learn More about Exoplanet Types Image 47 Image 48: HD 40307 g, a super earth exoplanet is on a poster featuring a skin diver without a parachute. Exoplanet Travel Bureau

• What Is an Exoplanet? | NASA Space Place – NASA Science for Kids

  What Is an Exoplanet? The Short Answer: All of the planets in our solar system orbit around the Sun. Planets that orbit around other stars are called exoplanets. All of the planets in our solar system orbit around the Sun. Planets that orbit around other stars are called exoplanets. Exoplanets are very hard to see directly with telescopes. They are hidden by the bright glare of the stars they orbit. [...] One way to search for exoplanets is to look for "wobbly" stars. A star that has planets doesn’t orbit perfectly around its center. From far away, this off-center orbit makes the star look like it’s wobbling. Image 13: an animation of a wobbling star and its transiting planet, from the side. An orbiting planet (small blue ball) causes a star (large yellow ball) to orbit slightly off-center. From a distance, this makes it look like the star is wobbling. [...] So far, thousands of planets have been discovered by the Kepler mission. And more will be found by NASA's Transiting Exoplanet Survey Satellite (TESS) mission, which is observing the entire sky to locate planets orbiting the nearest and brightest stars. We now know that exoplanets are very common in the universe. And future NASA missions have been planned to discover many more! ### Want to learn even more about exoplanets? Visit NASA Exoplanets 101. article last updated January 10, 2022

• Exoplanet - Wikipedia

  The convention for naming exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union (IAU). For exoplanets orbiting a single star, the IAU designation is formed by taking the designated or proper name of its parent star, and adding a lower case letter. Letters are given in order of each planet's discovery around the parent star, so that the first planet discovered in a system is designated "b" (the parent star is [...] Initially, the most known exoplanets were massive planets that orbited very close to their parent stars. Astronomers were surprised by these "hot Jupiters", because theories of planetary formation had indicated that giant planets should only form at large distances from stars. But eventually more planets of other sorts were found, and it is now clear that hot Jupiters make up the minority of exoplanets. In 1999, Upsilon Andromedae became the first main-sequence star known to have multiple [...] > Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars, brown dwarfs or stellar remnants and that have a mass ratio with the central object below the L4/L5 instability (M/Mcentral < 2/(25+√621)) are "planets" (no matter how they formed).

• Exoplanets - Center for Astrophysics | Harvard & Smithsonian

  Since large planets orbiting close to their stars block more light, most exoplanets we know of are larger than Earth. In fact, the most common exoplanet types identified so far are super-Earths, which are probably rocky planets larger in size than Earth, and mini-Neptunes, worlds slightly smaller than Uranus and Neptune. [...] Exoplanets Breadcrumb Home > Research > Research Topics > Exoplanets Until the 1990s, the only planets we knew existed were in orbit around the Sun. Since 1992, astronomers have discovered thousands of exoplanets: worlds in orbit around other stars. Based on the data we have, researchers think there could be hundreds of billions of planets in the Milky Way alone. [...] Astronomers first discovered exoplanets orbiting neutron stars in 1992, followed by the first exoplanets in orbit around ordinary stars in 1995. Those first worlds were much larger than Jupiter, and detected by the way their gravity tugged back on their host stars.

• Instance Of

  Q838795