This is How the Habitable Exoplanets Catalog Might Look in Twenty Years
The following graphic and caption depicts a fictional optimistic scenario of the detection of life on a nearby exoplanet in the next twenty years. The graphic was created to visualize and compare future goals with our current knowledge of habitable worlds. However, getting actual planet images of Earth-like planets, and detecting life, might even take much longer than twenty years.


First Detection of Extraterrestrial Life Outside the Solar System

Astronomers are reporting today the detection of the faint signal of biological activity in the exoplanet Dagobah in the Alpha Centauri System. Dagobah, named after the swamp planet of the Star Wars films, was known to have oceans and continents just like Earth albeit slightly higher temperatures. It was discovered last year but it took additional observations by the Terrestrial Planet Imager (TPI) to detect the spectral biosignatures of a global vegetation cover. This is the first evidence of extraterrestrial life besides our Solar System and opens the possibility of many similar worlds among the hundreds of known habitable exoplanets and exomoons. There is no evidence yet of the presence of intelligent life or even animal life on this planet. Radio telescopes will be concentrating effort on detecting any artificial signals from Dagobah in the following years.

A few fun facts about the graphic
  • The graphic is dated April 1st, 2034 in the credit line. We have been detecting exoplanets for the last 22 years, since 1992.
  • The title 'First detection of extraterrestrial life outside the Solar System' implies that we already detected life in the Solar System within the next twenty years, probably on Mars or Europa.
  • The planets are not real but the name of the stellar systems are. Some already have planets (i.e. Alpha Centauri and Tau Ceti).
  • The names of the planets are taken from Sci-Fi films: Dagobah from Star Wars, New Earth (aka Planet Bob) from Titan A.E., Thermia from Galaxy Quest, Qo'noS (aka Kronos) from Star Trek, and Pandora from Avatar. Today we use cryptic names for exoplanets but we might start using more popular names in the near future.
  • The graphic suggests that the pictures of the planets are actual images. Planets that are farther away are shown with a lower spatial resolution as expected. Today we cannot yet see any Earth-size planet as a single point of light and having the technology to see details on them might take much longer than twenty years.
  • The total number of exoplanets (no exomoons yet) is based on extrapolating some current results but there is no guarantee that we will maintain such a pace of discovery. Probably the numbers are on the high end of the spectrum.

This is How the Habitable Exoplanets Catalog Should Look Now
(using the same format as the graphic above)


Astronomers know that most of the nearly 1,800 confirmed exoplanets that have been detected so far are not good for life. They are either too big or too hot for life. Only up to twenty exoplanets appear to have some of the physical requirements for life. The graphic above shows the top five. All are larger than Earth (aka Super-Earths) and we are not sure about their potential for life since we know very little of them, and therefore classified as just potentially habitable. Future observations with larger and better telescopes will be necessary to identify those really habitable or even those inhabited, if any.

This is How the Habitable Exoplanets Catalog Looks Now
(the usual format listing all objects)

Click image for more details, or click here for larger version.

These are artistic representations of all the planets around other stars (exoplanets) with any potential to support surface life as we know it. All of them are larger than Earth and we are less certain about their composition and habitability, but they represent the best objects of interest for future observations. They are ranked from best to worst with the Earth Similarity Index (ESI), a measure of Earth-likeness, but none yet seems to be a true Earth-like planet. This selection of worlds is also subject to change as new interpretations or astronomical observations are made. Earth, Mars, Jupiter, and Uranus are shown for scale on the right.

Potentially Habitable Exoplanets
Database Subterran
(Mars-size)		 Terran
(Earth-size)		 Superterran
(Super-Earth)		 Total
Habitable Exoplanets Catalog (1)
 0 0 20 20
NASA Kepler Candidates (2)
 1 7 61 69

All Known Exoplanets

Confirmed Exoplanets (3)

NASA Kepler Candidates (4)

1,779

3,845

Table Notes
(1) The database of the Habitable Exoplanets Catalog includes both confirmed and unconfirmed exoplanets.
(2) Numbers based on the NASA Kepler Candidates waiting for confirmation, but some already confirmed.
(3) Confirmed planets listed by the Extrasolar Planets Encyclopedia plus any recent corrections.
(4) Most of NASA Kepler Candidates are still unconfirmed exoplanets.

And The Habitable Exoplanets Catalog Twenty Years Ago
(there was no need for it)


By April 1st, 1994 we only knew of two confirmed exoplanets discovered by the Arecibo Observatory on 1992. At that time there was no need for a catalog of exoplanets less a catalog of habitable exoplanets. First potentially habitable exoplanets were discovered by 2010.