Key points from the poster
- The poster paints more than 500 exoplanets found before October 2015, about a quarter of those known at the time.
- Planets are placed by mean temperature (left to right, -200 °C to 2000 °C) and density (bottom to top, 1 to 20 g/cm3).
- Nine Solar System bodies are included for comparison: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
- Text panels describe four classes: gas giants, gas dwarfs, ice giants and terrestrial (rocky) planets.
- The poster says about 1 in 5 Sun-like stars has an Earth-sized planet in the habitable zone, implying more than 20 billion potentially habitable planets in the Milky Way.
All figures are from the graphic, drawn by Martin Vargic of Halcyon Maps.
The exoplanets infographic in text
Title: Exoplanets. Credit: “Drawn by Martin Vargic, www.halcyonmaps.com”. Each planet is a painted sphere with its catalogue name underneath, such as HD80606 b, Kepler 62 f or 55 Cancri e. Cold gas giants sit to the left, hot Jupiters and lava worlds to the right, and dense rocky planets towards the top.
Temperature axis (bottom, “Mean temperature”): -200 °C / -328 °F, -150 °C / -238 °F, -100 °C / -148 °F, -50 °C / -58 °F, 0 °C / -32 °F (sic), 100 °C / 212 °F, 200 °C / 392 °F, 500 °C / 932 °F, 1000 °C / 1832 °F, 1500 °C / 2732 °F, 2000 °C / 3632 °F.
Density axis (right, “Density”): 1 g/cm3 / 62 lb/ft3, 2 g/cm3 / 125 lb/ft3, 3 g/cm3 / 187 lb/ft3, 4 g/cm3 / 250 lb/ft3, 5 g/cm3 / 312 lb/ft3, 6 g/cm3 / 374 lb/ft3, 7 g/cm3 / 437 lb/ft3, 8 g/cm3 / 500 lb/ft3, 10 g/cm3 / 624 lb/ft3, 20 g/cm3 / 1247 lb/ft3.
Some of the largest labelled planets: HD 33564 b, PSR B1620-26 b, 47 Uma d, HD 125612 d, HR 8799 e, HD 5891 b, Kepler 75 b, Kepler 14 b, GU Piscium B, WASP-89 b, XO-3 b, HAT-P-7b and Kepler-76 b.
Introduction (summary, figures as printed): The visualisation shows more than 500 exoplanets found before October 2015, about a quarter of all exoplanets then known, arranged by temperature and density. It names super-earths, hot jupiters, hot neptunes, water worlds, gas dwarfs and superdense diamond planets. Each picture is based on the planet’s estimated radius and temperature, with density, age and stellar metallicity also considered, and “the true nature of the portrayed exoplanets might turn out to be radically different”. Nearly 2000 exoplanets were known “as of October 2005” (sic), most found with the Kepler space telescope. There is estimated to be at least one planet per star on average. Around 1 in 5 Sun-like stars has a planet 1 to 2 times the size of Earth in the habitable zone, which puts the number of potentially habitable planets in the Milky Way above 20 billion. The closest confirmed exoplanet is given as Gliese 674 b, 14.8 light years away, with unconfirmed candidates around Tau Ceti and Alpha Centauri b.
History panel (summary): In 1584 Giordano Bruno said there were “countless suns and countless earths” and was accused of heresy. The panel traces the idea back to ancient Greece, then to Copernicus and to Edwin Hubble’s finding that nebulae were galaxies far outside our own, and says almost the whole 20th century passed without convincing proof of planets around other stars.
Detection panel (summary): Peter van de Kamp’s late 1960s claim of two planets around Barnard’s Star was not verified. The panel dates the first widely accepted detection to 1993, when Alexander Wolszczan reported planet-sized objects orbiting a pulsar, and the first planet around a Sun-like star to 1995, when Michel Mayor and Didier Queloz found one at 51 Pegasi using the radial velocity method. It ends with the French CoRoT mission (2006) and NASA’s Kepler Space Telescope (2009), which it calls the most successful exoplanet mission.
Gas giants: the easiest to find and a large share of known exoplanets. The panel says PSR B1620-26 b was the first exoplanet found. Most known gas giants are “hot Jupiters” orbiting closer to their stars than Mercury is to the Sun, some with clouds of alkali metals, silicon or iron, and heat can inflate them into low density “puffy planets”. Above about 10 Jupiter masses objects are often classed as brown dwarfs, or “failed stars”.
Gas dwarfs: smaller gaseous planets, usually smaller than Neptune and sometimes smaller than Earth, thought to be rare. The closest Solar System equivalent named is Saturn’s moon Titan.
Ice giants: mostly heavier elements such as oxygen, nitrogen and carbon rather than hydrogen and helium, like Uranus and Neptune. Most known ice giant exoplanets are “hot neptunes” orbiting close to their stars.
Terrestrial planets: rocky worlds of silicates and heavy metals. Most known ones are “super-earths”. Other classes named are lava planets, water worlds, carbon planets with “graphite mountains and diamond cores” and cannonball planets made almost entirely of iron.
How the count has grown since 2015
The poster gives nearly 2,000 known exoplanets in late 2015. Wikipedia, citing the NASA Exoplanet Archive, lists 6,445 confirmed exoplanets in 4,834 planetary systems as of 8 October 2026 [3]. Vargic has since made a larger poster, The Exoplanet Zoo, which says more than 6,140 worlds in over 4,500 star systems have been confirmed since the first in 1992 [2].
The closest known exoplanet has also changed. Proxima Centauri b, announced in August 2016, orbits the nearest star to the Sun at about 4.2 light years [4], far closer than the poster’s Gliese 674 b at 14.8 light years.
Notes on this infographic
- First exoplanets. The poster dates Wolszczan’s pulsar planets to 1993. They were announced by Aleksander Wolszczan and Dale Frail on 9 January 1992, around the pulsar PSR B1257+12, and are generally considered the first definitive detection [3].
- PSR B1620-26 b. The poster says it was the first exoplanet found. Its planetary nature was announced in 1993 [5], after the 1992 pulsar planets [3].
- Fahrenheit error. The axis prints 0 °C as -32 °F; it should be 32 °F.
- Typing errors. “October 2005” in the introduction should be October 2015, as the first sentence says. The text also prints “galaxiest”, “infathomable”, “succesful” and “othe”.
- Artist’s impressions. As the poster says, the planets’ appearance is estimated from radius and temperature and may be very different in reality.
Questions about exoplanets
How many exoplanets have been discovered?
Wikipedia, citing the NASA Exoplanet Archive, lists 6,445 confirmed exoplanets in 4,834 planetary systems as of 8 October 2026 [3]. When Martin Vargic drew this poster in late 2015, nearly 2,000 exoplanets were known, most of them found with the Kepler space telescope. The poster shows more than 500 of them, about a quarter of the total at the time.
What was the first exoplanet discovered?
The first definitive detection is generally credited to Aleksander Wolszczan and Dale Frail, who announced planets around the pulsar PSR B1257+12 on 9 January 1992 [3]. The poster names PSR B1620-26 b as the first exoplanet found, but its planetary nature was announced in 1993 [5]. The first planet around a Sun-like star was found at 51 Pegasi in 1995 by Michel Mayor and Didier Queloz.
What is the closest exoplanet to Earth?
Proxima Centauri b is the closest known exoplanet, orbiting the nearest star to the Sun at about 4.2 light years [4]. It was announced in August 2016, after the poster was made. The poster gives Gliese 674 b, 14.8 light years away, as the closest confirmed exoplanet, with unconfirmed candidates around Tau Ceti and Alpha Centauri b.
How many habitable planets are there in the Milky Way?
The poster puts the number of potentially habitable planets in the Milky Way at more than 20 billion. It bases this on the estimate that around 1 in 5 Sun-like stars has a planet 1 to 2 times the size of Earth in its habitable zone. It also says there is estimated to be at least one planet per star on average.
Sources
- Halcyon Maps, Exoplanets, Martin Vargic’s original page for this poster.
- Halcyon Maps, The Exoplanet Zoo, his later, larger exoplanet poster.
- Wikipedia, Exoplanet.
- Wikipedia, Proxima Centauri b.
- Wikipedia, PSR B1620-26.
Last reviewed 29 October 2026
